Publications by authors named "Dimitar Gavrilov"

39 Publications

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

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

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

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
February 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 Mar 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
January 2021

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

Genomic Analysis of Historical Cases with Positive Newborn Screens for Short-Chain Acyl-CoA Dehydrogenase Deficiency Shows That a Validated Second-Tier Biochemical Test Can Replace Future Sequencing.

Int J Neonatal Screen 2020 Jun 26;6(2). Epub 2020 May 26.

Department of Pediatrics, University of California, San Francisco, CA 94158 USA.

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is a rare autosomal recessive disorder of β-oxidation caused by pathogenic variants in the gene. Analyte testing for SCADD in blood and urine, including newborn screening (NBS) using tandem mass spectrometry (MS/MS) on dried blood spots (DBSs), is complicated by the presence of two relatively common variants (c.625G>A and c.511C>T). Individuals homozygous for these variants or compound heterozygous do not have clinical disease but do have reduced short-chain acyl-CoA dehydrogenase (SCAD) activity, resulting in elevated blood and urine metabolites. As part of a larger study of the potential role of exome sequencing in NBS in California, we reviewed sequence and MS/MS data from DBSs from a cohort of 74 patients identified to have SCADD. Of this cohort, approximately 60% had one or more of the common variants and did not have the two rare variants, and thus would need no further testing. Retrospective analysis of ethylmalonic acid, glutaric acid, 2-hydroxyglutaric acid, 3-hydroxyglutaric acid, and methylsuccinic acid demonstrated that second-tier testing applied before the release of the newborn screening result could reduce referrals by over 50% and improve the positive predictive value for SCADD to above 75%.
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http://dx.doi.org/10.3390/ijns6020041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423011PMC
June 2020

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

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

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

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

Mitochondrial 3-Hydroxy-3-Methylglutaryl-CoA Synthase Deficiency: Unique Presenting Laboratory Values and a Review of Biochemical and Clinical Features.

JIMD Rep 2018 14;40:63-69. Epub 2017 Oct 14.

Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.

We report an 8-month-old infant with decreased consciousness after a febrile episode and reduced oral intake. He was profoundly acidotic but his lactate was normal. Serum triglycerides were markedly elevated and HDL cholesterol was very low. The urine organic acid analysis during the acute episode revealed a complex pattern of relative hypoketotic dicarboxylic aciduria, suggestive of a potential fatty acid oxidation disorder. MRI showed extensive brain abnormalities concerning for a primary energy deficiency. Whole exome sequencing revealed heterozygotic HMGCS2 variants. HMGCS2 encodes mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase-2 (HMGCS2), which catalyzes the irreversible and rate-limiting reaction of ketogenesis in the mitochondrial matrix. Autosomal recessive HMG-CoA synthase deficiency (HMGCS2D) is characterized by hypoketotic hypoglycemia, vomiting, lethargy, and hepatomegaly after periods of prolonged fasting or illness. A retrospective analysis of the urine organic acid analysis identified 4-hydrox-6-methyl-2-pyrone, a recently reported putative biomarker of HMGCS2D. There was also a relative elevation of plasma acetylcarnitine as previously reported in one case. Our patient highlights a unique presentation of HMGCS2D caused by novel variants in HMGCS2. This is the first report of HMGCS2D with a significantly elevated triglyceride level and decreased HDL cholesterol level at presentation. Given this, we suggest that HMGCS2D should be considered in the differential diagnosis when hypertriglyceridemia, or low HDL cholesterol levels are seen in a child who presents with acidosis, mild ketosis, and mental status changes after illness or prolonged fasting. Although HMGCS2D is a rare disorder with nonspecific symptoms, with the advent of next-generation sequencing, and the recognition of novel biochemical biomarkers, the incidence of this condition may become better understood.
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http://dx.doi.org/10.1007/8904_2017_59DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6122033PMC
October 2017

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

Cyanide-Nitroprusside Colorimetric Assay: A Rapid Colorimetric Screen for Urinary Cystine.

J Appl Lab Med 2017 Jul;2(1):55-64

Division of Nephrology and Hypertension.

Background: Cystinuria is an autosomal recessive disorder resulting in poor proximal tubule reabsorption of cystine in the nephron, increasing the risk of cystine stone formation. A fast, inexpensive assay to screen for urinary cystine is needed because cystine stones are difficult to noninvasively differentiate from more common calcium-containing ones. Tandem mass spectrometry (MS/MS) is sensitive and specific but is labor-intensive and costly. Alternatively, a colorimetric assay is fast and cost-effective; however, creatinine interference is an issue.

Methods: A published cyanide-nitroprusside colorimetric assay was modified for a high-throughput microplate format. Creatinine interference was reduced using 0.1 mol/L PBS and a standard reaction time of 60 s and was further corrected using a formula derived from the slope of multiple creatinine standard curves.

Results: The limit of blank was determined to be 2.6 mg/L, the limit of detection 11.9 mg/L, and the limit of quantitation 15.3 mg/L. The analytic measurement range was established as 15.3-100 mg/L cystine. Intraassay and interassay CV was calculated to be 9.6% and 8.0%, respectively, for a high-level cystine concentration (83.6 mg/L). Low-level cystine (36.4 mg/L) intraassay and interassay CV was determined to be 18.1% and 17.6%, respectively. Passing-Bablok regression analysis of colorimetric vs LC-MS/MS results revealed a slope of 1.10 and y intercept of -7.14 mg/L, with an overall bias of 2% by Bland-Altman plot analysis.

Conclusions: We analytically validated a rapid colorimetric assay suitable to quantify urinary cystine. The effect of thiol drugs on this assay remains to be determined.
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http://dx.doi.org/10.1373/jalm.2016.022582DOI Listing
July 2017

Simultaneous Testing for 6 Lysosomal Storage Disorders and X-Adrenoleukodystrophy in Dried Blood Spots by Tandem Mass Spectrometry.

Clin Chem 2016 09 20;62(9):1248-54. Epub 2016 Jul 20.

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

Background: Newborn screening for lysosomal storage disorders (LSD) has revealed that late-onset variants of these conditions are unexpectedly frequent and therefore may evade diagnosis. We developed an efficient and cost-effective multiplex assay to diagnose six LSDs and several peroxisomal disorders in patients presenting with diverse phenotypes at any age.

Methods: Three 3-mm dried blood spot (DBS) punches were placed into individual microtiter plates. One disc was treated with a cocktail containing acid sphingomyelinase-specific substrate and internal standard (IS). To the second DBS we added a cocktail containing substrate and IS for β-glucosidase, acid α-glucosidase, α-galactosidase A, galactocerebrosidase, and α-L-iduronidase. The third DBS was extracted with methanol containing d4-C26 lysophosphatidylcholine as IS and stored until the enzyme plates were combined and purified by liquid-liquid and solid-phase extraction. The extracts were evaporated, reconstituted with the extract from the lysophosphatidylcholine plate, and analyzed by flow injection tandem mass spectrometry.

Results: Reference intervals were determined by analysis of 550 samples from healthy controls. DBS from confirmed patients with 1 of the 6 LSDs (n = 33), X-adrenoleukodystrophy (n = 9), or a peroxisomal biogenesis disorder (n = 5), as well as carriers for Fabry disease (n = 17) and X-adrenoleukodystrophy (n = 5), were analyzed for assay validation. Prospective clinical testing of 578 samples revealed 25 patients affected with 1 of the detectable conditions.

Conclusions: Our flow injection tandem mass spectrometry approach is amenable to high-throughput population screening for Hurler disease, Gaucher disease, Niemann-Pick A/B disease, Pompe disease, Krabbe disease, Fabry disease, X-adrenoleukodystrophy, and peroxisomal biogenesis disorder in DBS.
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http://dx.doi.org/10.1373/clinchem.2016.256255DOI Listing
September 2016

Silent Tyrosinemia Type I Without Elevated Tyrosine or Succinylacetone Associated with Liver Cirrhosis and Hepatocellular Carcinoma.

Hum Mutat 2016 10 8;37(10):1097-105. Epub 2016 Aug 8.

Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota.

Tyrosinemia type I (TYRSN1, TYR I) is caused by fumarylacetoacetate hydrolase (FAH) deficiency and affects approximately one in 100,000 individuals worldwide. Pathogenic variants in FAH cause TYRSN1, which induces cirrhosis and can progress to hepatocellular carcinoma (HCC). TYRSN1 is characterized by the production of a pathognomonic metabolite, succinylacetone (SUAC) and is included in the Recommended Uniform Screening Panel for newborns. Treatment intervention is effective if initiated within the first month of life. Here, we describe a family with three affected children who developed HCC secondary to idiopathic hepatosplenomegaly and cirrhosis during infancy. Whole exome sequencing revealed a novel homozygous missense variant in FAH (Chr15(GRCh38):g.80162305A>G; NM_000137.2:c.424A > G; NP_000128.1:p.R142G). This novel variant involves the catalytic pocket of the enzyme, but does not result in increased SUAC or tyrosine, making the diagnosis of TYRSN1 problematic. Testing this novel variant using a rapid, in vivo somatic mouse model showed that this variant could not rescue FAH deficiency. In this case of atypical TYRSN1, we show how reliance on SUAC as a primary diagnostic test can be misleading in some patients with this disease. Augmentation of current screening for TYRSN1 with targeted sequencing of FAH is warranted in cases suggestive of the disorder.
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http://dx.doi.org/10.1002/humu.23047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5108417PMC
October 2016

Outcome of Whole Exome Sequencing for Diagnostic Odyssey Cases of an Individualized Medicine Clinic: The Mayo Clinic Experience.

Mayo Clin Proc 2016 Mar;91(3):297-307

Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN; Center for Individualized Medicine, Mayo Clinic, Rochester, MN.

Objective: To describe the experience and outcome of performing whole-exome sequencing (WES) for resolution of patients on a diagnostic odyssey in the first 18 months of an individualized medicine clinic (IMC).

Patients And Methods: The IMC offered WES to physicians of Mayo Clinic practice for patients with suspected genetic disease. DNA specimens of the proband and relatives were submitted to WES laboratories. We developed the Genomic Odyssey Board with multidisciplinary expertise to determine the appropriateness for IMC services, review WES reports, and make the final decision about whether the exome findings explain the disease. This study took place from September 30, 2012, to March 30, 2014.

Results: In the first 18 consecutive months, the IMC received 82 consultation requests for patients on a diagnostic odyssey. The Genomic Odyssey Board deferred 7 cases and approved 75 cases to proceed with WES. Seventy-one patients met with an IMC genomic counselor. Fifty-one patients submitted specimens for WES testing, and the results have been received for all. There were 15 cases in which a diagnosis was made on the basis of WES findings; thus, the positive diagnostic yield of this practice was 29%. The mean cost per patient for this service was approximately $8000. Medicaid supported 27% of the patients, and 38% of patients received complete or partial insurance coverage.

Conclusion: The significant diagnostic yield, moderate cost, and notable health marketplace acceptance for WES compared with conventional genetic testing make the former method a rational diagnostic approach for patients on a diagnostic odyssey.
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http://dx.doi.org/10.1016/j.mayocp.2015.12.018DOI Listing
March 2016

Anesthesia and organic aciduria: is the use of lactated Ringer's solution absolutely contraindicated?

Paediatr Anaesth 2015 Aug 5;25(8):807-817. Epub 2015 May 5.

Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA.

Background: Organic acidurias (OAs) are rare inborn errors of metabolism that can present with various neurologic manifestations, propensity for acute metabolic decompensation with anion-gap metabolic acidosis, developmental delay, poor feeding, and failure to thrive.

Objective: In this case series, we outline the anesthetic management and perioperative outcomes of OA patients.

Methods: We reviewed demographic characteristics, comorbidities, and perioperative course of patients with four different OAs who underwent anesthetic care at our institution between January 1, 2000, and December 31, 2013.

Results: Eleven patients with OA underwent 19 anesthetic procedures, of which 13 were <2 h in duration and seven were outpatient procedures. One patient with methylmalonic acidemia developed metabolic acidosis during a 10-h procedure with substantial blood loss but lacked evidence that this acidosis could be attributed to his underlying metabolic disease. The patients who received hydration with lactated Ringer's solution and/or nitrous oxide anesthetic had a perioperative course free of metabolic complication. Two patients died within 30 days of surgery from causes likely to be unrelated to anesthetic exposure.

Conclusions: Our patients with various forms of metabolically compensated OAs tolerated anesthetics for surgical procedures without metabolic decompensation, even when lactated Ringer's solution was used for hydration. Measures to prevent protein catabolism and intraoperative events that may precipitate metabolic acidosis, in addition to close monitoring of acid-base status during more extensive procedures, must be part of perioperative treatment of these patients.
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http://dx.doi.org/10.1111/pan.12673DOI Listing
August 2015

Newborn screening for lysosomal storage disorders.

Semin Perinatol 2015 Apr 16;39(3):206-16. Epub 2015 Apr 16.

Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, MN, USA; Department of Medical Genetics, Mayo Clinic College of Medicine, Rochester, MN.

Every newborn in the U.S. is screened for at least 29 disorders, where evidence suggests that early detection is possible and beneficial. With new or improved treatment options and development of high-throughput screening tests, additional conditions have been proposed for inclusion in newborn screening programs. Among those are several lysosomal storage disorders that have been evaluated in limited pilot studies or that are already included in a few national or international newborn screening programs. These conditions include Pompe disease, Niemann-Pick type A/B disease, Fabry disease, Krabbe disease, Mucopolysaccharidoses types I and II, and Gaucher disease. Here, we review the current state of newborn screening for these lysosomal storage disorders.
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http://dx.doi.org/10.1053/j.semperi.2015.03.005DOI Listing
April 2015

Outcomes of four patients with homocysteine remethylation disorders detected by newborn screening.

Genet Med 2016 Feb 9;18(2):162-7. Epub 2015 Apr 9.

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

Purpose: We evaluated the clinical outcome in homocysteine remethylation disorders following newborn screening (NBS) and initiation of early specific treatment.

Methods: Five patients with remethylation disorders were included in this study.

Results: Two asymptomatic patients (one with cblG and one with cblE) were identified by NBS using an approach that combines a postanalytical interpretive tool (available on the Region 4 Stork (R4S) collaborative project website, http://www.clir-r4s.org) and a second-tier test for total homocysteine determination. Both the initial screening and the second-tier test are performed on the same blood spot, with no additional patient contact, resulting in no false-positive outcomes. Two additional patients with methylenetetrahydrofolate reductase deficiency were detected by NBS using low methionine as a marker. Although already symptomatic despite the early diagnosis, the latter two patients greatly improved with treatment and their outcomes are compared with that of another patient with methylenetetrahydrofolate reductase deficiency and significant morbidity who was diagnosed clinically at 3 months of age.

Conclusion: Early detection by NBS and timely and specific treatment considerably improve at least short-term outcomes of homocysteine remethylation disorders. When a remethylation disorder is suspected, group-specific treatment could be started prior to the completion of in vitro confirmatory testing because all disorders from this group require similar intervention.
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http://dx.doi.org/10.1038/gim.2015.45DOI Listing
February 2016

Measurement of psychosine in dried blood spots--a possible improvement to newborn screening programs for Krabbe disease.

J Inherit Metab Dis 2015 Sep 12;38(5):923-9. Epub 2015 Mar 12.

Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN, 55905, USA.

Background: Newborn screening (NBS) for Krabbe disease (KD) in New York and Missouri is conducted by measuring galactocerebrosidase (GALC) activity using tandem mass spectrometry (MS/MS). These NBS efforts have shown that the incidence of KD is unexpectedly low (1:400,000) while many individuals (ca. 1:6000) with reduced GALC activity and genotypes of uncertain significance are detected and subjected to follow up testing. Psychosine (PSY) is a putative marker of KD progression and can be measured in dried blood spots (DBS). We sought to determine the role that PSY levels play in NBS for KD, follow up, and treatment monitoring.

Methods: PSY was eluted from DBS with methanol containing N,N-dimethyl-D-erythro-sphingosine as internal standard (IS). Liquid chromatography-MS/MS was conducted over 17 minutes in the multiple reaction monitoring positive mode to follow the precursor to product species transitions for PSY and IS. Separation of the structural isomers PSY and glucosylsphingosine was accomplished by hydrophilic interaction liquid chromatography.

Results: Pre-analytical and analytical factors were studied and revealed satisfactory results. PSY was also measured in DBS collected from controls (range: <8 nmol/L, N = 220), KD patients at various disease stages (range: 8-112, N = 26), and GALC mutation carriers (range: <15 nmol/L, N = 18).

Conclusions: PSY measurement in DBS could serve as a 2nd tier assay in NBS for KD, simplify and reduce the cost of follow up protocols, help determine disease progression, and be used to monitor KD patients following hematopoietic stem cell transplantation. However, additional chronological measurements of PSY in KD patients are required to confirm these possibilities.
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http://dx.doi.org/10.1007/s10545-015-9822-zDOI Listing
September 2015

Streamlined determination of lysophosphatidylcholines in dried blood spots for newborn screening of X-linked adrenoleukodystrophy.

Mol Genet Metab 2015 Jan 27;114(1):46-50. Epub 2014 Nov 27.

Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. Electronic address:

Background: Pre-symptomatic hematopoietic stem cell transplantation is essential to achieve best possible outcomes for patients with the childhood cerebral form of X-linked adrenoleukodystrophy (X-ALD). We describe a high-throughput method for measurement of C20-C26 lysophosphatidylcholines (LPCs) and biochemical diagnosis of X-ALD using the same dried blood spots (DBS) routinely used for newborn screening.

Methods: LPCs are extracted from 3-mm DBS punch with methanol containing an isotopically labeled LPC as internal standard. This extract is transferred to a 96-well plate, evaporated and then reconstituted in mobile phase for flow injection analysis tandem mass spectrometry (FIA-MS/MS) in selected reaction monitoring mode for measurement of four different LPCs (C20, C22, C24, C26) and the internal standard (d4-C26-LPC). Analysis time is 1.5min per sample.

Results: The mean CVs from the intra- and inter-assay experiments for LPCs were 6.3-15.1% for C20-LPC, 4.4-18.6% for C22-LPC and 4.5-14.3% for C24-LPC. Limits of detection were determined for C20-LPC (LOD=0.03μg/mL), C22-LPC (0.03μg/mL), C24-LPC (0.03μg/mL) and C26-LPC (0.01μg/mL). Reference ranges were established from DBS of 130 newborns and 20 adults. Samples of patients with X-ALD (n=16), peroxisomal biogenesis disorders (n=8), and X-ALD carriers (n=12) were analyzed blindly and all were correctly identified.

Conclusion: Analysis of LPC species by FIA-MS/MS is a fast, simple and reliable method to screen for X-ALD and other peroxisomal disorders in DBS. To maximize specificity, abnormal results can be verified by a 2nd tier assay using LC-MS/MS.
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http://dx.doi.org/10.1016/j.ymgme.2014.11.013DOI Listing
January 2015

A macro-enzyme cause of an isolated increase of alkaline phosphatase.

Clin Chim Acta 2015 Feb 21;440:169-71. Epub 2014 Nov 21.

Division of Laboratory Genetics, Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, United States; Department of Pediatrics and Adolescent Medicine, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, United States.

Background: Macroenzyme complexes of serum enzymes and antibody can increase the circulating enzymatic activity and may lead to unnecessary additional testing and procedures. Laboratory physicians and scientists need to be aware of techniques to identify macroenzyme complexes when suspected.

Case Report: To investigate the possibility of a macro-alkaline phosphatase in the serum of a 74 year old male with persistently increased alkaline phosphatase we coupled a protein A/G agarose affinity chromatography technique with isoenzyme electrophoresis to look for the presence of macro-alkaline phosphatase.

Results: The majority of the alkaline phosphatase activity in the patient's serum sample was bound to the column and only a minor fraction (25%) of alkaline phosphatase activity was present in the column flow-through. The alkaline phosphatase activity was also found to co-elute with the immunoglobulins in the patient sample. The alkaline phosphatase activity in a control serum sample concurrently treated in the same manner did not bind to the column and was found in the column flow-through.

Conclusion: The use of protein A/G agarose affinity chromatography is a rapid and simple method that can be applied to the investigation of other macro-enzyme complexes.
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http://dx.doi.org/10.1016/j.cca.2014.11.017DOI Listing
February 2015

High-throughput immunoassay for the biochemical diagnosis of Friedreich ataxia in dried blood spots and whole blood.

Clin Chem 2013 Oct 9;59(10):1461-9. Epub 2013 Jul 9.

Division of Laboratory Genetics, Department of Laboratory Medicine and Pathology, and.

Background: Friedreich ataxia (FRDA) is caused by reduced frataxin (FXN) concentrations. A clinical diagnosis is typically confirmed by DNA-based assays for GAA-repeat expansions or mutations in the FXN (frataxin) gene; however, these assays are not applicable to therapeutic monitoring and population screening. To facilitate the diagnosis and monitoring of FRDA patients, we developed an immunoassay for measuring FXN.

Methods: Antibody pairs were used to capture FXN and an internal control protein, ceruloplasmin (CP), in 15 μL of whole blood (WB) or one 3-mm punch of a dried blood spot (DBS). Samples were assayed on a Luminex LX200 analyzer and validated according to standard criteria.

Results: The mean recovery of FXN from WB and DBS samples was 99%. Intraassay and interassay imprecision (CV) values were 4.9%-13% and 9.8%-16%, respectively. The FXN limit of detection was 0.07 ng/mL, and the reportable range of concentrations was 2-200 ng/mL. Reference adult and pediatric FXN concentrations ranged from 15 to 82 ng/mL (median, 33 ng/mL) for DBS and WB. The FXN concentration range was 12-22 ng/mL (median, 15 ng/mL) for FRDA carriers and 1-26 ng/mL (median 5 ng/mL) for FRDA patients. Measurement of the FXN/CP ratio increased the ability to distinguish between patients, carriers, and the reference population.

Conclusions: This assay is applicable to the diagnosis and therapeutic monitoring of FRDA. This assay can measure FXN and the control protein CP in both WB and DBS specimens with minimal sample requirements, creating the potential for high-throughput population screening of FRDA.
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http://dx.doi.org/10.1373/clinchem.2013.207472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914541PMC
October 2013

Aripiprazole and trazodone cause elevations of 7-dehydrocholesterol in the absence of Smith-Lemli-Opitz Syndrome.

Mol Genet Metab 2013 Sep-Oct;110(1-2):176-8. Epub 2013 Apr 10.

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

Screening for Smith-Lemli-Opitz Syndrome (SLOS) using elevated 7-dehydrocholesterol (7DHC) as a marker is sensitive, but not always specific. Elevations of 7DHC can be seen in patients who do not have a defect in 7-dehydrocholesterol reductase. These results have often been attributed to medication artifacts, but specific causes have not been well reported. We examined the medical records of patients with elevated 7DHC to determine if they had been diagnosed with SLOS; and if they had not, to identify any common medications that may have caused the elevations. We found three individuals who were affected with SLOS, and 22 with elevated 7DHC in the absence of SLOS. Seven of these individuals underwent molecular testing which showed no mutations, while the other 15 were excluded based on clinical findings and other testing. The medication history of these individuals revealed aripiprazole and trazodone as common medications to all the false positive results.
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http://dx.doi.org/10.1016/j.ymgme.2013.04.004DOI Listing
March 2014

Enhanced interpretation of newborn screening results without analyte cutoff values.

Authors:
Gregg Marquardt Robert Currier David M S McHugh Dimitar Gavrilov Mark J Magera Dietrich Matern Devin Oglesbee Kimiyo Raymond Piero Rinaldo Emily H Smith Silvia Tortorelli Coleman T Turgeon Fred Lorey Bridget Wilcken Veronica Wiley Lawrence C Greed Barry Lewis François Boemer Roland Schoos Sandrine Marie Marie-Françoise Vincent Yuri Cleverthon Sica Mouseline Torquado Domingos Khalid Al-Thihli Graham Sinclair Osama Y Al-Dirbashi Pranesh Chakraborty Mark Dymerski Cory Porter Adrienne Manning Margretta R Seashore Jonessy Quesada Alejandra Reuben Petr Chrastina Petr Hornik Iman Atef Mandour Sahar Abdel Atty Sharaf Olaf Bodamer Bonifacio Dy Jasmin Torres Roberto Zori David Cheillan Christine Vianey-Saban David Ludvigson Adrya Stembridge Jim Bonham Melanie Downing Yannis Dotsikas Yannis L Loukas Vagelis Papakonstantinou Georgios S A Zacharioudakis Ákos Baráth Eszter Karg Leifur Franzson Jon J Jonsson Nancy N Breen Barbara G Lesko Stanton L Berberich Kimberley Turner Margherita Ruoppolo Emanuela Scolamiero Italo Antonozzi Claudia Carducci Ubaldo Caruso Michela Cassanello Giancarlo la Marca Elisabetta Pasquini Iole Maria Di Gangi Giuseppe Giordano Marta Camilot Francesca Teofoli Shawn M Manos Colleen K Peterson Stephanie K Mayfield Gibson Darrin W Sevier Soo-Youn Lee Hyung-Doo Park Issam Khneisser Phaidra Browning Fizza Gulamali-Majid Michael S Watson Roger B Eaton Inderneel Sahai Consuelo Ruiz Rosario Torres Mary A Seeterlin Eleanor L Stanley Amy Hietala Mark McCann Carlene Campbell Patrick V Hopkins Monique G de Sain-Van der Velden Bert Elvers Mark A Morrissey Sherlykutty Sunny Detlef Knoll Dianne Webster Dianne M Frazier Julie D McClure David E Sesser Sharon A Willis Hugo Rocha Laura Vilarinho Catharine John James Lim S Graham Caldwell Kathy Tomashitis Daisy E Castiñeiras Ramos Jose Angel Cocho de Juan Inmaculada Rueda Fernández Raquel Yahyaoui Macías José María Egea-Mellado Inmaculada González-Gallego Carmen Delgado Pecellin Maria Sierra García-Valdecasas Bermejo Yin-Hsiu Chien Wuh-Liang Hwu Thomas Childs Christine D McKeever Tijen Tanyalcin Mahera Abdulrahman Cecilia Queijo Aída Lemes Tim Davis William Hoffman Mei Baker Gary L Hoffman

Genet Med 2012 Jul 16;14(7):648-55. Epub 2012 Feb 16.

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

Purpose: To improve quality of newborn screening by tandem mass spectrometry with a novel approach made possible by the collaboration of 154 laboratories in 49 countries.

Methods: A database of 767,464 results from 12,721 cases affected with 60 conditions was used to build multivariate pattern recognition software that generates tools integrating multiple clinically significant results into a single score. This score is determined by the overlap between normal and disease ranges, penetration within the disease range, differences between conditions, and weighted correction factors.

Results: Ninety tools target either a single condition or the differential diagnosis between multiple conditions. Scores are expressed as the percentile rank among all cases with the same condition and are compared to interpretation guidelines. Retrospective evaluation of past cases suggests that these tools could have avoided at least half of 279 false-positive outcomes caused by carrier status for fatty-acid oxidation disorders and could have prevented 88% of known false-negative events.

Conclusion: Application of this computational approach to raw data is independent from single analyte cutoff values. In Minnesota, the tools have been a major contributing factor to the sustained achievement of a false-positive rate below 0.1% and a positive predictive value above 60%.
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http://dx.doi.org/10.1038/gim.2012.2DOI Listing
July 2012