Publications by authors named "Piero Rinaldo"

99 Publications

Maternal serum lipidomics identifies lysophosphatidic acid as a predictor of small for gestational age neonates.

Mol Omics 2021 Sep 14. Epub 2021 Sep 14.

International Center for Maternal and Newborn Health, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.

To discover lipidomic alterations during pregnancy in mothers who subsequently delivered small for gestational age (SGA) neonates and identify predictive lipid markers that can help recognize and manage these mothers, we carried out untargeted lipidomics on maternal serum samples collected between 24-28 weeks of gestation. We used a nested case-control study design and serum from mothers who delivered SGA and appropriate for gestational age babies. We applied untargeted lipidomics using mass spectrometry to characterize lipids and discover changes associated with SGA births during pregnancy. Multivariate pattern recognition software Collaborative Laboratory Integrated Reports (CLIR) was used for the post-analytical recognition of range differences in lipid ratios that could differentiate between SGA and control mothers and their integration for complete separation between the two groups. Here, we report changes in lipids from serum collected during pregnancy in mothers who delivered SGA neonates. In contrast to normal pregnancies where lysophosphatidic acid increased over the course of the pregnancy owing to increased activity of lysophospholipase D, we observed a decrease (32%; = 0.05) of 20:4-lysophosphatidic acid in SGA mothers, which could potentially compromise fetal growth and development. Integration of lipid ratios in an interpretive tool (CLIR) could completely separate SGA mothers from controls demonstrating the power of untargeted lipidomic analyses for identifying novel predictive biomarkers. Additional studies are required for further assessment of the lipid biomarkers identified in this report.
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http://dx.doi.org/10.1039/d1mo00131kDOI Listing
September 2021

Limited Expansion of Human Hepatocytes in FAH/-Deficient Swine.

Tissue Eng Part A 2021 Oct 7. Epub 2021 Oct 7.

Department of Surgery, Mayo Clinic, Rochester, Minnesota, USA.

The mammalian liver's regenerative ability has led researchers to engineer animals as incubators for expansion of human hepatocytes. The expansion properties of human hepatocytes in immunodeficient mice are well known. However, little has been reported about larger animals that are more scalable and practical for clinical purposes. Therefore, we engineered immunodeficient swine to support expansion of human hepatocytes and identify barriers to their clinical application. Immunodeficient swine were engineered by knockout of the recombinase-activating gene 2 () and fumarylacetoacetate hydrolase (FAH). Immature human hepatocytes (ihHCs) were injected into fetal swine by intrauterine cell transplantation (IUCT) at day 40 of gestation. Human albumin was measured as a marker of engraftment. Cytotoxicity against ihHCs was measured in transplanted piglets and control swine. We initially detected higher levels of human albumin in cord blood of newborn FAH/-deficient (FR) pigs compared with immunocompetent controls (196.26 ng/dL vs. 39.29 ng/dL,  = 0.008), indicating successful engraftment of ihHCs after IUCT and adaptive immunity in the fetus. Although rare hepatocytes staining positive for human albumin were observed, levels of human albumin did not rise after birth, but declined, suggesting rejection of xenografted ihHCs. Cytotoxicity against ihHCs increased after birth by 3.8% (95% CI: [2.1%-5.4%],  < 0.001) and inversely correlated with declining levels of human albumin ( = 2.1 × 10,  = 0.17). Circulating numbers of T cells and B cells were negligible in FR pigs. However, circulating natural killer (NK) cells exerted cytotoxicity against ihHCs. NK cell activity was lower in immunodeficient piglets after IUCT than in naive controls (30.4% vs. 40.1%,  = 0.011, 95% CI for difference [2.7%-16.7%]). In conclusion, ihHCs were successfully engrafted in FR swine after IUCT. NK cells were a significant barrier to expansion of hepatocytes. New approaches are needed to overcome this hurdle and allow large-scale expansion of human hepatocytes in immunodeficient swine. Impact statement There is currently a need for robust expansion of human hepatocytes. We describe an immunodeficient swine model into which we engrafted immature human hepatocytes (ihHCs). We identified the mechanism of the eventual graft rejection by the intact NK cell population, which has not been previously shown to have a significant role in xenograft rejection. By both improving engraftment and reducing NK cell-mediated cytotoxicity toward the graft through intrauterine cell transfer, we confirmed the presence of residual adaptive immunity in this model of immunodeficiency and the ability to induce hyposensitization in the NK cell population by taking advantage of the fetal microenvironment.
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http://dx.doi.org/10.1089/ten.TEA.2021.0057DOI Listing
October 2021

The low excretor phenotype of glutaric acidemia type I is a source of false negative newborn screening results and challenging diagnoses.

JIMD Rep 2021 Jul 5;60(1):67-74. Epub 2021 Apr 5.

Biochemical Genetics Laboratory, Mayo Clinic Rochester Minnesota USA.

Background: Glutaric acidemia type I (GA1) is an organic acidemia that is often unrecognized in the newborn period until patients suffer an acute encephalopathic crisis, which can be mistaken for nonaccidental trauma. Presymptomatic identification of GA1 patients is possible by newborn screening (NBS). However, the biochemical "low-excretor" (LE) phenotype with nearly normal levels of disease metabolites can be overlooked, which may result in untreated disease and irreversible neurological sequelae. The LE phenotype is also a potential source of false negative (FN) NBS results that merits further investigation.

Methods: Samples from six LE GA1 patients were analyzed by biochemical and molecular methods and newborn screen outcomes were retrospectively investigated.

Results: Five LE GA1 patients were identified that had normal NBS results and three of these presented clinically with GA1 symptoms. One additional symptomatic patient was identified who did not undergo screening. Semiquantitative urine organic acid analysis was consistent with a GA1 diagnosis in two (33%) of the six patients, while plasma glutarylcarnitine was elevated in four (67%) of the six and urine glutarylcarnitine was elevated in four (80%) of five patients. Five variants were identified in these patients; three of which have not been previously linked to the biochemical LE phenotype.

Conclusions: The data presented here raise awareness of potential FN NBS results for LE GA1 patients. The LE phenotype is not protective against adverse clinical outcomes, and the possibility of FN NBS results calls for high vigilance amongst clinicians, even in the setting of a normal NBS result.
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http://dx.doi.org/10.1002/jmd2.12217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260482PMC
July 2021

Validation of a multiplex flow immunoassay for detection of IgG antibodies against SARS-CoV-2 in dried blood spots.

PLoS One 2021 28;16(5):e0252621. Epub 2021 May 28.

Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America.

Background: Dried blood spots (DBS) are an established specimen type for clinical testing given their low cost, ease of collection and storage, and convenient shipping capabilities through the postal system. These attributes are complementary to the expansion of SARS-CoV-2 serologic testing, which may be used to inform community seroprevalence rates.

Methods: The Luminex xMAP SARS-CoV-2 Multi-Antigen assay utilizes magnetic beads labeled with three viral antigens (nucleocapsid [NC], receptor binding domain [RBD], spike S1 subunit) to detect anti-viral IgG-class antibodies, and has Food and Drug Administration (FDA) Emergency Use Authorization (EUA) for use in serum and plasma. This assay was modified for use with DBS and validated against paired sera tested by one of two reference assays: the Roche Diagnostics Elecsys anti-SARS-CoV-2 ECLIA or the Euroimmun anti-SARS-CoV-2 IgG ELISA.

Results: 159 paired DBS and serum specimens analyzed using the modified Luminex xMAP assay on DBS and the reference methods on serum showed an overall concordance of 96.9% (154/159). Use of multivariate pattern recognition software (CLIR) for post-analytical interpretation of the Luminex xMAP DBS assay results, instead of manufacturer provided interpretive thresholds, increased overall qualitative result concordance to 99.4% (158/159) between the modified Luminex xMAP DBS and reference results.

Conclusions: Use of DBS for detection of antibodies against SARS-CoV-2 provides comparable results to those obtained using serum. DBS concordance was improved with multivariate pattern recognition software (CLIR). We demonstrate that DBS are a reliable specimen type for SARS-CoV-2 antibody detection using the modified Luminex xMAP assay.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0252621PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8162624PMC
June 2021

A new D-galactose treatment monitoring index for PGM1-CDG.

J Inherit Metab Dis 2021 09 22;44(5):1263-1271. Epub 2021 Jun 22.

Department of Laboratory Medicine and Pathology, Biochemical Genetics Laboratory, Mayo Clinic, Rochester, Minnesota, USA.

Phosphoglucomutase 1 (PGM1) catalyzes the interconversion of glucose-6-phosphate to glucose-1-phosphate and is a key enzyme of glycolysis, glycogenesis, and glycogenolysis. PGM1 deficiency (OMIM: 614921) was initially defined as a glycogen storage disorder (type XIV), and later re-classified as a PGM1-congenital disorder of glycosylation (PGM1-CDG). Serum transferrin (Tf) glycan isoform analysis by liquid chromatography-mass spectrometry (LC-MS) is used as a primary diagnostic screen tool, and reveals a very unique CDG profile described as a mixture of CDG-type I and CDG-type II patterns. Oral d-galactose supplementation shows significant clinical and metabolic improvements, which are indicated by the Tf glycan isoform normalization over time in patients with PGM1-CDG. Thus, there is a need for biomarkers to guide d-galactose dosage in patients in order to maintain effective and safe drug levels. Here, we present a simplified algorithm called PGM1-CDG Treatment Monitoring Index (PGM1-TMI) for assessing the response of PGM1-CDG patients to d-galactose supplementation. For our single-center cohort of 16 PGM1-CDG patients, the Tf glycan profile analysis provided the biochemical diagnosis in all of them. In addition, the PGM1-TMI was reduced in PGM1-CDG patients under d-galactose supplementation as compared with their corresponding values before treatment, indicating that glycosylation proceeds towards normalization. PGM1-TMI allows tracking Tf glycan isoform normalization over time when the patients are on d-galactose supplementation.
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http://dx.doi.org/10.1002/jimd.12406DOI Listing
September 2021

A Novel Approach to Improve Newborn Screening for Congenital Hypothyroidism by Integrating Covariate-Adjusted Results of Different Tests into CLIR Customized Interpretive Tools.

Int J Neonatal Screen 2021 Apr 23;7(2). Epub 2021 Apr 23.

Norwegian National Unit for Newborn Screening, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, 0424 Oslo, Norway.

Newborn screening for congenital hypothyroidism remains challenging decades after broad implementation worldwide. Testing protocols are not uniform in terms of targets (TSH and/or T4) and protocols (parallel vs. sequential testing; one or two specimen collection times), and specificity (with or without collection of a second specimen) is overall poor. The purpose of this retrospective study is to investigate the potential impact of multivariate pattern recognition software (CLIR) to improve the post-analytical interpretation of screening results. Seven programs contributed reference data (N = 1,970,536) and two sets of true (TP, N = 1369 combined) and false (FP, N = 15,201) positive cases for validation and verification purposes, respectively. Data were adjusted for age at collection, birth weight, and location using polynomial regression models of the fifth degree to create three-dimensional regression surfaces. Customized Single Condition Tools and Dual Scatter Plots were created using CLIR to optimize the differential diagnosis between TP and FP cases in the validation set. Verification testing correctly identified 446/454 (98%) of the TP cases, and could have prevented 1931/5447 (35%) of the FP cases, with variable impact among locations (range 4% to 50%). CLIR tools either as made here or preferably standardized to the recommended uniform screening panel could improve performance of newborn screening for congenital hypothyroidism.
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http://dx.doi.org/10.3390/ijns7020023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8167643PMC
April 2021

Bilateral subdural hematomas and retinal hemorrhages mimicking nonaccidental trauma in a patient with D-2-hydroxyglutaric aciduria.

JIMD Rep 2021 Mar 20;58(1):21-28. Epub 2020 Nov 20.

Department of Clinical Genomics Mayo Clinic Rochester Minnesota USA.

Introduction: Nonaccidental trauma (NAT) is considered when pediatric patients present with intracranial injuries and a negative history of an accidental injury or concomitant medical diagnosis. The evaluation of NAT should include the consideration of possible medical causes including coagulation, hematologic, metabolic and other genetic disorders, as well as witnessed and unwitnessed accidental injuries.

Case Presentation: We present a 7-month-old male with spells and incidental findings of bilateral subdural hematomas, retinal hemorrhages, and secondary macrocephaly, leading to investigation for NAT. Biochemical analysis showed excretion of a large amount of D-2-hydroxyglutaric in urine consistent with a biochemical diagnosis of D-2-hydroxyglutaric aciduria, a rare neurometabolic disorder characterized by developmental delay, epilepsy, hypotonia, and psychomotor retardation. None of these symptoms were present in our patient at the time of diagnosis. Molecular genetic testing revealed a pathogenic splice site variant (c.685-2A>G) and a variant of uncertain significance (c.1256G>T) with evidence of pathogenicity in the gene, consistent with a molecular diagnosis of D-2-hydroxyglutaric aciduria type I (OMIM #600721).

Conclusion: Since several metabolic disorders, including D-2-hydroxyglutaric aciduria type I, can present solely with symptoms suggestive of NAT (subdural and retinal hemorrhages), an early metabolic evaluation by urine organic acid analysis should be included in clinical protocols evaluating NAT. A methodical and nonjudgmental approach coordinated between pediatricians and metabolic specialists is also necessary to ensure that rare genetic conditions are not overlooked to prevent devastating social, legal, and financial consequences of suspected child abuse.
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http://dx.doi.org/10.1002/jmd2.12188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7932861PMC
March 2021

The Clinical Impact of CLIR Tools toward Rapid Resolution of Post-Newborn Screening Confirmatory Testing for X-Linked Adrenoleukodystrophy in California.

Int J Neonatal Screen 2020 Sep 5;6(3):62. Epub 2020 Aug 5.

Genetic Disease Screening Program, California Department of Public Health, Richmond, CA 94804, USA; (J.M.); (S.S.).

Since the start of X-linked adrenoleukodystrophy (ALD) newborn screening in California, more than half of the diagnosed cases were found to have an ATP binding cassette subfamily D member 1 () gene variant of uncertain significance (VUS). To determine retrospectively the likelihood that these were true positive cases, we used a web-based post-analytical tool in Collaborative Laboratory Integrated Reports (CLIR). Confirmatory plasma very long-chain fatty-acids (VLCFA) profiles for ALD screen positive infant boys were run through the CLIR ALD tool. We compared the distribution by variant classification (pathogenic, likely pathogenic, VUS, and no variant) with the CLIR tool score interpretation (non-informative, possibly ALD, likely ALD, and very likely ALD) and the current case diagnosis. The study showed that CLIR tool positive interpretations were consistent with 100% of the pathogenic and likely pathogenic variants on the gene if a more conservative guideline was used. The tool interpretations were also consistent with screened cases that were determined to not have disease (our no-disorder group). The CLIR tool identified 19 diagnosed ALD cases with VUS to be potential false positives, representing a 40% reduction among all diagnosed ALD cases with VUS. The reduction could be extended to 65% if a more aggressive threshold was used. Identifying such preventable false positives could alleviate the follow-up burden for patients, their families, and California Special Care Centers.
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http://dx.doi.org/10.3390/ijns6030062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7570356PMC
September 2020

Performance of Expanded Newborn Screening in Norway Supported by Post-Analytical Bioinformatics Tools and Rapid Second-Tier DNA Analyses.

Int J Neonatal Screen 2020 Sep 27;6(3):51. Epub 2020 Jun 27.

Department of Paediatrics, Division of Paediatric and Adolescent Medicine, Oslo University Hospital, 0424 Oslo, Norway; (G.G.); (R.L.); (T.R.).

In 2012, the Norwegian newborn screening program (NBS) was expanded (eNBS) from screening for two diseases to that for 23 diseases (20 inborn errors of metabolism, IEMs) and again in 2018, to include a total of 25 conditions (21 IEMs). Between 1 March 2012 and 29 February 2020, 461,369 newborns were screened for 20 IEMs in addition to phenylketonuria (PKU). Excluding PKU, there were 75 true-positive (TP) (1:6151) and 107 (1:4311) false-positive IEM cases. Twenty-one percent of the TP cases were symptomatic at the time of the NBS results, but in two-thirds, the screening result directed the exact diagnosis. Eighty-two percent of the TP cases had good health outcomes, evaluated in 2020. The yearly positive predictive value was increased from 26% to 54% by the use of the Region 4 Stork post-analytical interpretive tool (R4S)/Collaborative Laboratory Integrated Reports 2.0 (CLIR), second-tier biochemical testing and genetic confirmation using DNA extracted from the original dried blood spots. The incidence of IEMs increased by 46% after eNBS was introduced, predominantly due to the finding of attenuated phenotypes. The next step is defining which newborns would truly benefit from screening at the milder end of the disease spectrum. This will require coordinated international collaboration, including proper case definitions and outcome studies.
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http://dx.doi.org/10.3390/ijns6030051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7570219PMC
September 2020

The Combined Impact of CLIR Post-Analytical Tools and Second Tier Testing on the Performance of Newborn Screening for Disorders of Propionate, Methionine, and Cobalamin Metabolism.

Int J Neonatal Screen 2020 Jun 10;6(2):33. Epub 2020 Apr 10.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA; (A.L.P.); (G.P.); (C.T.); (D.M.); (D.O.); (K.R.); (S.T.); (P.R.).

The expansion of the recommend uniform screening panel to include more than 50 primary and secondary target conditions has resulted in a substantial increase of false positive results. As an alternative to subjective manipulation of cutoff values and overutilization of molecular testing, here we describe the performance outcome of an algorithm for disorders of methionine, cobalamin, and propionate metabolism that includes: (1) first tier screening inclusive of the broadest available spectrum of markers measured by tandem mass spectrometry; (2) integration of all results into a score of likelihood of disease for each target condition calculated by post-analytical interpretive tools created byCollaborative Laboratory Integrated Reports (CLIR), a multivariate pattern recognition software; and (3) further evaluation of abnormal scores by a second tier test measuring homocysteine, methylmalonic acid, and methylcitric acid. This approach can consistently reduce false positive rates to a <0.01% level, which is the threshold of precision newborn screening. We postulate that broader adoption of this algorithm could lead to substantial savings in health care expenditures. More importantly, it could prevent the stress and anxiety experienced by many families when faced with an abnormal newborn screening result that is later resolved as a false positive outcome.
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http://dx.doi.org/10.3390/ijns6020033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423003PMC
June 2020

Incorporation of Second-Tier Biomarker Testing Improves the Specificity of Newborn Screening for Mucopolysaccharidosis Type I.

Int J Neonatal Screen 2020 03 7;6(1):10. Epub 2020 Feb 7.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA; (J.M.L.); (A.L.W.); (G.P.); (A.L.S.); (D.G.); (D.O.); (K.R.); (D.M.); (P.R.).

Enzyme-based newborn screening for Mucopolysaccharidosis type I (MPS I) has a high false-positive rate due to the prevalence of pseudodeficiency alleles, often resulting in unnecessary and costly follow up. The glycosaminoglycans (GAGs), dermatan sulfate (DS) and heparan sulfate (HS) are both substrates for α-l-iduronidase (IDUA). These GAGs are elevated in patients with MPS I and have been shown to be promising biomarkers for both primary and second-tier testing. Since February 2016, we have measured DS and HS in 1213 specimens submitted on infants at risk for MPS I based on newborn screening. Molecular correlation was available for 157 of the tested cases. Samples from infants with MPS I confirmed by molecular analysis all had significantly elevated levels of DS and HS compared to those with confirmed pseudodeficiency and/or heterozygosity. Analysis of our testing population and correlation with molecular results identified few discrepant outcomes and uncovered no evidence of false-negative cases. We have demonstrated that blood spot GAGs analysis accurately discriminates between patients with confirmed MPS I and false-positive cases due to pseudodeficiency or heterozygosity and increases the specificity of newborn screening for MPS I.
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http://dx.doi.org/10.3390/ijns6010010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7422968PMC
March 2020

Immune dysfunction in MGAT2-CDG: A clinical report and review of the literature.

Am J Med Genet A 2021 01 12;185(1):213-218. Epub 2020 Oct 12.

Department of Pediatrics, School of Medicine, University of Washington, Seattle, Washington, USA.

Glycosylation is a critical post/peri-translational modification required for the appropriate development and function of the immune system. As an example, abnormalities in glycosylation can cause antibody deficiency and reduced lymphocyte signaling, although the phenotype can be complex given the diverse roles of glycosylation. Human MGAT2 encodes N-acetylglucosaminyltransferase II, which is a critical enzyme in the processing of oligomannose to complex N-glycans. Complex N-glycans are essential for immune system functionality, but only one individual with MGAT2-CDG has been described to have an abnormal immunologic evaluation. MGAT2-CDG (CDG-IIa) is a congenital disorder of glycosylation (CDG) associated with profound global developmental disability, hypotonia, early onset epilepsy, and other multisystem manifestations. Here, we report a 4-year old female with MGAT2-CDG due to a novel homozygous pathogenic variant in MGAT2, a 4-base pair deletion, c.1006_1009delGACA. In addition to clinical features previously described in MGAT2-CDG, she experienced episodic asystole, persistent hypogammaglobulinemia, and defective ex vivo mitogen and antigen proliferative responses, but intact specific vaccine antibody titers. Her infection history has been mild despite the testing abnormalities. We compare this patient to the 15 previously reported patients in the literature, thus expanding both the genotypic and phenotypic spectrum for MGAT2-CDG.
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http://dx.doi.org/10.1002/ajmg.a.61914DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8098812PMC
January 2021

Novel biomarkers and age-related metabolite correlations in plasma and dried blood spots from patients with succinic semialdehyde dehydrogenase deficiency.

Orphanet J Rare Dis 2020 09 23;15(1):261. Epub 2020 Sep 23.

Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences Building Room 210C, Washington State University, 412 E. Spokane Falls Boulevard, Spokane, WA, 99202-2131, USA.

Background: Previous work has identified age-related negative correlations for γ-hydroxybutyric acid (GHB) and γ-aminobutyric acid (GABA) in plasma of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD). Using plasma and dried blood spots (DBS) collected in an ongoing natural history study, we tested the hypothesis that other biomarkers would follow a similar age-related negative correlation as seen for GHB/GABA. Samples (mixed sex) included: patients (n = 21 unique samples, 1-39.5 yrs) and parallel controls (n = 9 unique samples, 8.4-34.8 yrs). Archival control data (DBS only; n = 171, 0.5-39.9 yrs) was also included.

Results: Metabolites assessed included amino acids (plasma, DBS) and acylcarnitines, creatine, creatinine, and guanidinoacetate (DBS only). Age-related negative correlations for glycine (plasma, DBS) and sarcosine (N-methylglycine, plasma) were detected, accompanied by elevated proline and decreased levels of succinylacetone, argininosuccinate, formaminoglutamate, and creatinine. Significantly low acylcarnitines were detected in patients across all chain lengths (short-, medium- and long-chain). Significant age-dependent positive correlations for selected acylcarnitines (C6-, C12DC(dicarboxylic)-, C16-, C16:1-, C18:1-, C18:2OH-carnitines) were detected in patients and absent in controls. Receiver operating characteristic (ROC) curves for all binary comparisons revealed argininosuccinate and succinylacetone to be the most discriminating biomarkers (area > 0.92).

Conclusions: Age-dependent acylcarnitine correlations may represent metabolic compensation responsive to age-related changes in GHB and GABA. Our study highlights novel biomarkers in SSADHD and expands the metabolic pathophysiology of this rare disorder of GABA metabolism.
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http://dx.doi.org/10.1186/s13023-020-01522-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510106PMC
September 2020

A Comparative Effectiveness Study of Newborn Screening Methods for Four Lysosomal Storage Disorders.

Int J Neonatal Screen 2020 Jun 30;6(2). Epub 2020 May 30.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.

Newborn screening for one or more lysosomal disorders has been implemented in several US states, Japan and Taiwan by multiplexed enzyme assays using either tandem mass spectrometry or digital microfluidics. Another multiplex assay making use of immunocapture technology has also been proposed. To investigate the potential variability in performance of these analytical approaches, we implemented three high-throughput screening assays for the simultaneous screening for four lysosomal disorders: Fabry disease, Gaucher disease, mucopolysaccharidosis type I, and Pompe disease. These assays were tested in a prospective comparative effectiveness study using nearly 100,000 residual newborn dried blood spot specimens. In addition, 2nd tier enzyme assays and confirmatory molecular genetic testing were employed. Post-analytical interpretive tools were created using the software Collaborative Laboratory Integrated Reports (CLIR) to determine its ability to improve the performance of each assay vs. the traditional result interpretation based on analyte-specific reference ranges and cutoffs. This study showed that all three platforms have high sensitivity, and the application of CLIR tools markedly improves the performance of each platform while reducing the need for 2nd tier testing by 66% to 95%. Moreover, the addition of disease-specific biochemical 2nd tier tests ensures the lowest false positive rates and the highest positive predictive values for any platform.
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http://dx.doi.org/10.3390/ijns6020044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423013PMC
June 2020

Does metabolomic profile differ with regard to birth weight?

Pediatr Res 2021 04 29;89(5):1144-1151. Epub 2020 Jun 29.

Faculty of Pharmaceutical Sciences, School of Health Science, Univeristy of Iceland, Reykjavik, Iceland.

Background: Macrosomia and child obesity are growing health-care issues worldwide. The purpose of the study was to evaluate how extremely high or low birth weight affects metabolic markers evaluated in newborn screening.

Methods: The study was register-based and included full-term singletons born in Iceland from 2009 to 2012 with newborn screening samples taken 72-96 h after birth. Three groups based on birth weight were compared: low birth weight (<2500 g), appropriate-for-gestational age, and extreme macrosomia (≥5000 g). The comparison was adjusted for possible confounding factors.

Results: Compared to appropriate-for-gestational age neonates, both low birth weight and extreme macrosomia were associated with higher levels of glutamic acid. The amino acids alanine and threonine were increased in low birth weight neonates. Free carnitine and some medium- and long-chain acylcarnitines were higher in low birth weight infants. Hydroxybutyrylcarnitine was lower in low birth weight infants, but higher in extremely macrosomic neonates. Acetylcarnitine was higher in low birth weight and extremely macrosomic neonates. Succinylcarnitine was lower and hexadecenoylcarnitine higher in macrosomic newborns.

Conclusion: Low birth weight and extremely macrosomic neonates show distinctive differences in their metabolomic profile compared to appropriate-for-gestational age newborns. The differences are not explained by gestational age.

Impact: The key message of this article is that both low birth weight and extremely macrosomic newborns show dissimilar metabolomic profiles compared to appropriate-for-gestational age neonates. The article contributes to knowledge on what affects evaluation of results in newborn screening. The impact of this article is to provide information on metabolism at both ends of the birth weight range after accounting for confounding factors including gestational age.
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http://dx.doi.org/10.1038/s41390-020-1033-0DOI Listing
April 2021

Laboratory monitoring of patients with hereditary tyrosinemia type I.

Mol Genet Metab 2020 08 6;130(4):247-254. Epub 2020 Jun 6.

Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, Rochester, MN, USA. Electronic address:

Background: The prognosis of patients with Hereditary Tyrosinemia Type 1 (HT-1) has greatly improved with early detection through newborn screening and the introduction of nitisinone (NTBC) therapy. A recent guideline calls for periodic monitoring of biochemical markers and NTBC levels to tailor treatment; however, this is currently only achieved through a combination of clinical laboratory tests. We developed a multiplexed assay measuring relevant amino acids, succinylacetone (SUAC), and NTBC in dried blood spots (DBS) to facilitate treatment monitoring.

Methods: Tyrosine, phenylalanine, methionine, NTBC and SUAC were eluted from DBS with methanol containing internal standards for each analyte and analyzed by liquid chromatography tandem mass spectrometry over 6.5 min in the multiple reaction monitoring positive mode.

Results: Pre-analytical and analytical factors were studied and demonstrated a reliable assay. Chromatography resolved an unknown substance that falsely elevates SUAC concentrations and was present in all samples. To establish control and disease ranges, the method was applied to DBS collected from controls (n = 284) and affected patients before (n = 2) and after initiation of treatment (n = 29). In the treated patients SUAC concentrations were within the normal range over a wide range of NTBC levels.

Conclusions: This assay enables combined, accurate measurement of revelevant metabolites and NTBC in order to simplify treatment monitoring of patients with HT-1. In addition, the use of DBS allows for specimen collection at home to facilitate more standardization in relation to drug and dietary treatment.
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http://dx.doi.org/10.1016/j.ymgme.2020.06.001DOI Listing
August 2020

Longitudinal metabolomics in dried bloodspots yields profiles informing newborn screening for succinic semialdehyde dehydrogenase deficiency.

JIMD Rep 2020 May 26;53(1):29-38. Epub 2020 Feb 26.

Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences Washington State University Spokane Washington.

Analyses of 19 amino acids, 38 acylcarnitines, and 3 creatine analogues (https://clir.mayo.edu) were implemented to test the hypothesis that succinic semialdehyde dehydrogenase deficiency (SSADHD) could be identified in dried bloodspots (DBS) using currently available newborn screening methodology. The study population included 17 post-newborn SSADHD DBS (age range 0.8-38 years; median, 8.2 years; 10 M; controls, 129-353 age-matched individuals, mixed gender) and 10 newborn SSADHD DBS (including first and second screens from 3 of 7 patients). Low (informative) markers in post-newborn DBS included C2- and C4-OH carnitines, ornithine, histidine and creatine, with no gender differences. For newborn DBS, informative markers included C2-, C3-, C4- and C4-OH carnitines, creatine and ornithine. Of these, only creatine demonstrated a significant change with age, revealing an approximate 4-fold decrease. We conclude that quantitation of short-chain acylcarnitines, creatine, and ornithine provides a newborn DBS profile with potential as a first tier screening tool for early detection of SSADHD. This first tier evaluation can be readily verified using a previously described second tier liquid chromatography-tandem mass spectrometry method for γ-hydroxybutyric acid in the same DBS. More extensive evaluation of this first/second tier screening approach is needed in a larger population.
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http://dx.doi.org/10.1002/jmd2.12075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203655PMC
May 2020

Correction to: Post-mortem tissue analyses in a patient with succinic semialdehyde dehydrogenase deficiency (SSADHD). I. Metabolomic outcomes.

Metab Brain Dis 2020 06;35(5):849-850

Department of Pharmacotherapy, Health Sciences Building Room, 210C, College of Pharmacy and Pharmaceutical Sciences, Washington State University, 412 E. Spokane Falls Boulevard, Spokane, WA, 99202-2131, USA.

Upon publication, it was noted that five of the on-line supplementary figures had incorrect figure: figure legend associations. These were supplementary Figs. 6, 7, 14, 15, and 23.
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http://dx.doi.org/10.1007/s11011-020-00569-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7228844PMC
June 2020

Post-mortem tissue analyses in a patient with succinic semialdehyde dehydrogenase deficiency (SSADHD). I. Metabolomic outcomes.

Metab Brain Dis 2020 04 14;35(4):601-614. Epub 2020 Mar 14.

Department of Pharmacotherapy, Health Sciences Building Room 210C, College of Pharmacy and Pharmaceutical Sciences, Washington State University, 412 E. Spokane Falls Boulevard, Spokane, WA, 99202-2131, USA.

Metabolomic characterization of post-mortem tissues (frontal and parietal cortices, pons, cerebellum, hippocampus, cerebral cortex, liver and kidney) derived from a 37 y.o. male patient with succinic semialdehyde dehydrogenase deficiency (SSADHD) was performed in conjunction with four parallel series of control tissues. Amino acids, acylcarnitines, guanidino- species (guanidinoacetic acid, creatine, creatinine) and GABA-related intermediates were quantified using UPLC and mass spectrometric methods that included isotopically labeled internal standards. Amino acid analyses revealed significant elevation of aspartic acid and depletion of glutamine in patient tissues. Evidence for disruption of short-chain fatty acid metabolism, manifest as altered C4OH, C5, C5:1, C5DC (dicarboxylic) and C12OH carnitines, was observed. Creatine and guanidinoacetic acids were decreased and elevated, respectively. GABA-associated metabolites (total GABA, γ-hydroxybutyric acid, succinic semialdehyde, 4-guanidinobutyrate, 4,5-dihydroxyhexanoic acid and homocarnosine) were significantly increased in patient tissues, including liver and kidney. The data support disruption of fat, creatine and amino acid metabolism as a component of the pathophysiology of SSADHD, and underscore the observation that metabolites measured in patient physiological fluids provide an unreliable reflection of brain metabolism.
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http://dx.doi.org/10.1007/s11011-020-00550-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7180121PMC
April 2020

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.

Genet Med 2020 06 24;22(6):1108-1118. Epub 2020 Feb 24.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.

Purpose: Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations.

Methods: PSY was extracted from dried blood spots or erythrocytes with methanol containing d-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry.

Results: Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT).

Conclusion: This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.
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http://dx.doi.org/10.1038/s41436-020-0764-yDOI Listing
June 2020

Multiplex testing for the screening of lysosomal storage disease in urine: Sulfatides and glycosaminoglycan profiles in 40 cases of sulfatiduria.

Mol Genet Metab 2020 02 5;129(2):106-110. Epub 2019 Nov 5.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.

Purpose: To describe an efficient and effective multiplex screening strategy for sulfatide degradation disorders and mucolipidosis type II/III (MLII/III) using 3 mL of urine.

Methods: Glycosaminoglycans were analyzed by liquid chromatography-tandem mass spectrometry. Matrix assisted laser desorption/ionization-time of flight tandem mass spectrometry was used to identify free oligosaccharides and identify 22 ceramide trihexosides and 23 sulfatides, which are integrated by 670 calculated ratios. Collaborative Laboratory Integrated Reports (CLIR; https://clir.mayo.edu) was used for post-analytical interpretation of the complex metabolite profile and to aid in the differential diagnosis of abnormal results.

Results: Multiplex analysis was performed on 25 sulfatiduria case samples and compiled with retrospective data from an additional 15 cases revealing unique patterns of biomarkers for each disorder of sulfatide degradation (MLD, MSD, and Saposin B deficiency) and for MLII/III, thus allowing the formulation of a novel algorithm for the biochemical diagnosis of these disorders.

Conclusions: Comprehensive and integrated urine screening could be very effective in the initial workup of patients suspected of having a lysosomal disorder as it covers disorders of sulfatide degradation and narrows down the differential diagnosis in patients with elevated glycosaminoglycans.
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http://dx.doi.org/10.1016/j.ymgme.2019.10.009DOI Listing
February 2020

Temporal metabolomics in dried bloodspots suggests multipathway disruptions in aldh5a1 mice, a model of succinic semialdehyde dehydrogenase deficiency.

Mol Genet Metab 2019 12 31;128(4):397-408. Epub 2019 Oct 31.

Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, United States of America. Electronic address:

Succinic semialdehyde dehydrogenase (SSADH) deficiency (SSADHD; OMIM 271980) is a rare disorder featuring accumulation of neuroactive 4-aminobutyric acid (GABA; γ-aminobutyric acid, derived from glutamic acid) and 4-hydroxybutyric acid (γ-hydroxybutyric acid; GHB, a short-chain fatty acid analogue of GABA). Elevated GABA is predicted to disrupt the GABA shunt linking GABA transamination to the Krebs cycle and maintaining the balance of excitatory:inhibitory neurotransmitters. Similarly, GHB (or a metabolite) is predicted to impact β-oxidation flux. We explored these possibilities employing temporal metabolomics of dried bloodspots (DBS), quantifying amino acids, acylcarnitines, and guanidino- metabolites, derived from aldh5a1, aldh5a1 and aldh5a1 mice (aldehyde dehydrogenase 5a1 = SSADH) at day of life (DOL) 20 and 42 days. At DOL 20, aldh5a1 mice had elevated C6 dicarboxylic (adipic acid) and C14 carnitines and threonine, combined with a significantly elevated ratio of threonine/[aspartic acid + alanine], in comparison to aldh5a1 mice. Conversely, at DOL 42 aldh5a1 mice manifested decreased short chain carnitines (C0-C6), valine and glutamine, in comparison to aldh5a1 mice. Guanidino species, including creatinine, creatine and guanidinoacetic acid, evolved from normal levels (DOL 20) to significantly decreased values at DOL 42 in aldh5a1 as compared to aldh5a1 mice. Our results provide a novel temporal snapshot of the evolving metabolic profile of aldh5a1 mice while highlighting new pathomechanisms in SSADHD.
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http://dx.doi.org/10.1016/j.ymgme.2019.10.003DOI Listing
December 2019

Cold storage of porcine hepatocyte spheroids for spheroid bioartificial liver.

Xenotransplantation 2019 07 10;26(4):e12512. Epub 2019 Apr 10.

Department of Surgery, Mayo Clinic, Rochester, Minnesota.

Background And Aims: Cell-based therapies for liver disease such as bioartificial liver rely on a large quantity and high quality of hepatocytes. Cold storage was previously shown to be a better way to preserve the viability and functionality of hepatocytes during transportation rather than freezing, but this was only proved at a lower density of rat hepatocytes spheroids. The purpose of this study was to optimize conditions for cold storage of high density of primary porcine hepatocyte spheroids.

Methods: Porcine hepatocytes were isolated by a three-step perfusion method; hepatocyte spheroids were formed by a 24 hours rocked culture technique. Hepatocyte cell density was 5 × 10 /mL in 1000 mL spheroid forming medium. Spheroids were then maintained in rocked culture at 37°C (control condition) or cold stored at 4°C for 24, 48 or 72 hours in four different cold storage solutions: histidine-tryptophan-ketoglutarate (HTK) alone; HTK + 1 mM deferoxamine (DEF); HTK + 5 mM N-acetyl-L-cysteine (NAC); and HTK + 1 mM DEF + 5 mM NAC. The viability, ammonia clearance, albumin production, gene expression, and functional activity of cytochrome P450 enzymes were measured after recovery from the cold storage.

Results: In this study, we observed that cold-induced injury was reduced by the addition of the iron chelator. Viability of HTK + DEF group hepatocyte spheroids was increased compared with other cold storage groups (P < 0.05). Performance metrics of porcine hepatocyte spheroids cold stored for 24 hours were similar to those in control conditions. The hepatocyte spheroids in control conditions started to lose their ability to clear ammonia while production of albumin was still active at 48 and 72 hours (P < 0.05). In contrast, the viability and functionality of hepatocyte spheroids including ammonia clearance and albumin secretion were preserved in HTK + DEF group at both 48- and 72-hour time points (P < 0.05).

Conclusions: The beneficial effects of HTK supplemented with DEF were more obvious after cold storage of high density of porcine hepatocyte spheroids for 72 hours. The porcine hepatocyte spheroids were above the cutoff criteria for use in a spheroid-based bioartificial liver.
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http://dx.doi.org/10.1111/xen.12512DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6717030PMC
July 2019

Multiplex Droplet Digital PCR Method Applicable to Newborn Screening, Carrier Status, and Assessment of Spinal Muscular Atrophy.

Clin Chem 2018 12 23;64(12):1753-1761. Epub 2018 Oct 23.

Departments of Laboratory Medicine and Pathology.

Background: Spinal muscular atrophy (SMA) is a progressive neuromuscular disorder with neuronal degeneration leading to muscular atrophy and respiratory failure. SMA is frequently caused by homozygous deletions that include exon 7 of the survival motor neuron gene , and its clinical course is influenced by the copy number of a nearby 5q paralog, . Multiple ligation probe amplification (MLPA) and real-time quantitative PCR (qPCR) can detect deletions. Yet, qPCR needs normalization or standard curves, and MLPA demands DNA concentrations above those obtainable from dried blood spots (DBSs). We developed a multiplex, droplet digital PCR (ddPCR) method for the simultaneous detection of deletions and copy number variation in DBS and other tissues. An Sanger sequencing process for DBS was also developed.

Methods: , , and concentrations were simultaneously measured with a Bio-Rad AutoDG and QX200 ddPCR system. A total of 1530 DBSs and 12 SMA patients were tested.

Results: Population studies confirmed 1 to 5 exon 7 copies detected in unaffected specimens, whereas patients with SMA revealed 0 copies. Intraassay and interassay imprecisions were <7.1% CV for individuals with ≥1 copies. Testing 12 SMA-positive samples resulted in 100% sensitivity and specificity.

Conclusions: This ddPCR method is sensitive, specific, and applicable to newborn screening and carrier status determination for SMA. It can also be incorporated with a parallel ddPCR T-cell excision circles assay for severe combined immunodeficiencies.
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http://dx.doi.org/10.1373/clinchem.2018.293712DOI Listing
December 2018

Newborn screening for proximal urea cycle disorders: Current evidence supporting recommendations for newborn screening.

Mol Genet Metab 2018 06 20;124(2):109-113. Epub 2018 Apr 20.

Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, Rochester, MN, USA.

Current newborn screening (NBS) for urea cycle disorders (UCD) is incomplete as only distal UCDs are included in most NBS programs by measuring elevated amino acid concentrations. NBS for the proximal UCDs involves the detection in NBS spots of low citrulline values, a finding which is often overlooked because it is considered to be inadequate. We retrospectively analyzed NBS blood spots from known UCD patients comparing the utility of the Region 4 Stork (R4S) interpretive tools to conventional cutoff based interpretation. This study shows the utility of R4S tools in detecting all UCDs, and provides evidence to support the nomination to add proximal UCDs to the recommended uniform screening panel.
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http://dx.doi.org/10.1016/j.ymgme.2018.04.006DOI Listing
June 2018

Allelic spectrum of formiminotransferase-cyclodeaminase gene variants in individuals with formiminoglutamic aciduria.

Mol Genet Genomic Med 2017 11 11;5(6):795-799. Epub 2017 Sep 11.

Mayo Clinic College of Medicine, Rochester, Minnesota.

Background: Elevated plasma and urine formiminoglutamic acid (FIGLU) levels are commonly indicative of formiminoglutamic aciduria (OMIM #229100), a poorly understood autosomal recessive disorder of histidine and folate metabolism, resulting from formiminotransferase-cyclodeaminase (FTCD) deficiency, a bifunctional enzyme encoded by FTCD.

Methods: In order to further understanding about the molecular alterations that contribute to FIGLU-uria, we sequenced FTCD in 20 individuals with putative FTCD deficiency and varying laboratory findings, including increased FIGLU excretion.

Results: Individuals tested had biallelic loss-of-function variants in protein-coding regions of FTCD. The FTCD allelic spectrum comprised of 12 distinct variants including 5 missense alterations that replace conserved amino acid residues (c.223A>C, c.266A>G, c.319T>C, c.430G>A, c.514G>T), an in-frame deletion (c.1373_1375delTGG), with the remaining alterations predicted to affect mRNA processing/stability. These included two frameshift variants (c.990dup, c.1366dup) and four nonsense variants (c.337C>T, c.451A>T, c.763C>T, c.1607T>A).

Conclusion: We observed additional FTCD alleles leading to urinary FIGLU elevations, and thus, providing molecular evidence of FTCD deficiency in cases identified by newborn screening or clinical biochemical genetic laboratory testing.
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http://dx.doi.org/10.1002/mgg3.333DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702579PMC
November 2017

Precision newborn screening for lysosomal disorders.

Genet Med 2018 08 9;20(8):847-854. Epub 2017 Nov 9.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA.

Purpose: The implementation of newborn screening for lysosomal disorders has uncovered overall poor specificity, psychosocial harm experienced by caregivers, and costly follow-up testing of false-positive cases. We report an informatics solution proven to minimize these issues.

Methods: The Kentucky Department for Public Health outsourced testing for mucopolysaccharidosis type I (MPS I) and Pompe disease, conditions recently added to the recommended uniform screening panel, plus Krabbe disease, which was added by legislative mandate. A total of 55,161 specimens were collected from infants born over 1 year starting from February 2016. Testing by tandem mass spectrometry was integrated with multivariate pattern recognition software (Collaborative Laboratory Integrated Reports), which is freely available to newborn screening programs for selection of cases for which a biochemical second-tier test is needed.

Results: Of five presumptive positive cases, one was affected with infantile Krabbe disease, two with Pompe disease, and one with MPS I. The remaining case was a heterozygote for the latter condition. The false-positive rate was 0.0018% and the positive predictive value was 80%.

Conclusion: Postanalytical interpretive tools can drastically reduce false-positive outcomes, with preliminary evidence of no greater risk of false-negative events, still to be verified by long-term surveillance.
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http://dx.doi.org/10.1038/gim.2017.194DOI Listing
August 2018

Moonlighting newborn screening markers: the incidental discovery of a second-tier test for Pompe disease.

Genet Med 2018 08 2;20(8):840-846. Epub 2017 Nov 2.

Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.

Purpose: To describe a novel biochemical marker in dried blood spots suitable to improve the specificity of newborn screening for Pompe disease.

Methods: The new marker is a ratio calculated between the creatine/creatinine (Cre/Crn) ratio as the numerator and the activity of acid α-glucosidase (GAA) as the denominator. Using Collaborative Laboratory Integrated Reports (CLIR), the new marker was incorporated in a dual scatter plot that can achieve almost complete segregation between Pompe disease and false-positive cases.

Results: The (Cre/Crn)/GAA ratio was measured in residual dried blood spots of five Pompe cases and was found to be elevated (range 4.41-13.26; 99%ile of neonatal controls: 1.10). Verification was by analysis of 39 blinded specimens that included 10 controls, 24 samples with a definitive classification (16 Pompe, 8 false positives), and 5 with genotypes of uncertain significance. The CLIR tool showed 100% concordance of classification for the 24 known cases. Of the remaining five cases, three p.V222M homozygotes, a benign variant, were classified by CLIR as false positives; two with genotypes of unknown significance, one likely informative, were categorized as Pompe disease.

Conclusion: The CLIR tool inclusive of the new ratio could have prevented at least 12 of 13 (92%) false-positive outcomes.
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http://dx.doi.org/10.1038/gim.2017.190DOI Listing
August 2018

A Droplet Digital PCR Method for Severe Combined Immunodeficiency Newborn Screening.

J Mol Diagn 2017 09;19(5):755-765

Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota; Department of Clinical Genomics, Mayo Clinic College of Medicine, Rochester, Minnesota. Electronic address:

Severe combined immunodeficiency (SCID) benefits from early intervention via hematopoietic cell transplantation to reverse T-cell lymphopenia (TCL). Newborn screening (NBS) programs use T-cell receptor excision circle (TREC) levels to detect SCID. Real-time quantitative PCR is often performed to quantify TRECs in dried blood spots (DBSs) for NBS. Yet, real-time quantitative PCR has inefficiencies necessitating normalization, repeat analyses, or standard curves. To address these issues, we developed a multiplex, droplet digital PCR (ddPCR) method for measuring absolute TREC amounts in one DBS punch. TREC and RPP30 levels were simultaneously measured with a Bio-Rad AutoDG and QX200 ddPCR system. DBSs from 610 presumed-normal, 29 lymphocyte-profiled, and 10 clinically diagnosed infants (1 X-linked SCID, 1 RAG1 Omenn syndrome, and other conditions) were tested. Control infants showed 14 to 474 TREC copies/μL blood. SCID infants, and other TCL conditions, had ≤15 TREC copies/μL. The ddPCR lower limit of quantitation was 14 TREC copies/μL, and the limit of detection was 4 TREC copies/μL. Intra-assay and interassay imprecision was <20% CV for DBSs at 54 to 60 TREC copies/μL. Testing 29 infants with known lymphocyte profiles resulted in a sensitivity of 88.9% and a specificity of 100% at TRECs <20 copies/μL. We developed a multiplex ddPCR method for the absolute quantitation of DBS TRECs that can detect SCID and other TCL conditions associated with absent or low TRECs and validated this method for NBS.
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http://dx.doi.org/10.1016/j.jmoldx.2017.05.011DOI Listing
September 2017

Chronic Phenotype Characterization of a Large-Animal Model of Hereditary Tyrosinemia Type 1.

Am J Pathol 2017 Jan 14;187(1):33-41. Epub 2016 Nov 14.

William J. von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, Minnesota; Department of Surgery, Mayo Clinic, Rochester, Minnesota. Electronic address:

Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disease caused by deficiency in fumarylacetoacetate hydrolase, the last enzyme in the tyrosine catabolic pathway. In this study, we investigated whether fumarylacetoacetate hydrolase deficient (FAH) pigs, a novel large-animal model of HT1, develop fibrosis and cirrhosis characteristic of the human disease. FAH pigs were treated with the protective drug 2-(2-nitro-4-trifluoromethylbenzoyl)-1, 3 cyclohexandione (NTBC) at a dose of 1 mg/kg per day initially after birth. After 30 days, they were assigned to one of three groups based on dosing of NTBC. Group 1 received ≥0.2 mg/kg per day, group 2 cycled on/off NTBC (0.05 mg/kg per day × 1 week/0 mg/kg per day × 3 weeks), and group 3 received no NTBC thereafter. Pigs were monitored for features of liver disease. Animals in group 1 continued to have weight gain and biochemical analyses comparable to wild-type pigs. Animals in group 2 had significant cessation of weight gain, abnormal biochemical test results, and various grades of fibrosis and cirrhosis. No evidence of hepatocellular carcinoma was detected. Group 3 animals declined rapidly, with acute liver failure. In conclusion, the FAH pig is a large-animal model of HT1 with clinical characteristics that resemble the human phenotype. Under conditions of low-dose NTBC, FAH pigs developed liver fibrosis and portal hypertension, and thus may serve as a large-animal model of chronic liver disease.
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http://dx.doi.org/10.1016/j.ajpath.2016.09.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5225308PMC
January 2017
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