Publications by authors named "John Roller"

12 Publications

  • Page 1 of 1

Gynecologic and obstetric management of women with von Willebrand disease: summary of 3 systematic reviews of the literature.

Blood Adv 2021 Oct 21. Epub 2021 Oct 21.

McMaster University, Canada.

Von Willebrand disease, (VWD) disproportionately affects women due to potential issues with heavy menstrual bleeding (HMB), delivery complications, and postpartum hemorrhage (PPH). To systematically synthesize the evidence regarding first line management of HMB, treatment of women requiring/desiring neuraxial analgesia, and management of PPH. We searched Medline and EMBASE through October 2019 for randomized trials, comparative observational studies, and case series comparing the effects of desmopressin, hormonal therapy, and tranexamic acid (TXA) on HMB, comparing different von Willebrand factor (VWF) levels in women with VWD undergoing labor and receiving neuraxial anesthesia and the effects of TXA on PPH We conducted duplicate study selection, data abstraction, and appraisal of risk of bias. Whenever possible, we conducted meta-analyses. We assessed the quality of the evidence using the GRADE approach. We included 1 randomized trial, 3 comparative observational studies and 10 case series. Moderate certainty evidence showed that desmopressin results in a smaller reduction of menstrual blood loss (difference in mean change from baseline, 41.6 [95% CI, 16.6 to 63.6] points in pictorial blood assessment chart score as compared to TXA. There was very low certainty evidence about how first line treatments compare against each other, the effects of different VWF levels in women receiving neuraxial anesthesia, and the effects of TXA administration postpartum. Most of the evidence relevant to the gynecologic and obstetric management of women with VWD addressed by most guidelines is very low quality. Future studies addressing research priorities will be key when updating such guidelines.
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http://dx.doi.org/10.1182/bloodadvances.2021005589DOI Listing
October 2021

Surgical management of patients with von Willebrand Disease: summary of 2 systematic reviews of the literature.

Blood Adv 2021 Oct 15. Epub 2021 Oct 15.

Department of Health Research Methods, Evidence and Impact, McMaster University, Canada.

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. The management of patients with VWD undergoing surgeries is crucial to prevent bleeding complications. To systematically summarize the evidence on the management of patients with VWD undergoing major and minor surgeries to support the development of practice guidelines. We searched Medline and EMBASE through October 2019 for randomized clinical trials (RCTs), comparative observational studies and case series comparing maintaining factor VIII levels or VWF levels >0.50 IU/mL for at least 3 days in patients undergoing major surgery, and options for perioperative management of patients undergoing minor surgery. Two authors screened, abstracted data, and assessed the risk of bias. We conducted meta-analysis when possible. We evaluated the certainty of the evidence using the GRADE approach. We included 7 case series for major surgeries and 2 RCTs and 12 case series for minor surgeries. Very low certainty evidence showed that maintaining factor VIII levels, or VWF levels > 0.50 IU/mL for at least 3 consecutive days showed excellent hemostatic efficacy (as labeled by the researchers) after 74-100% of major surgeries. Low to very low certainty evidence showed that prescribing tranexamic acid and increasing VWF levels to 0.50 IU/mL resulted in less bleeding complications after minor procedures compared to increasing VWF levels to 0.50 IU/mL alone. Given the low-quality evidence to guide management decisions, a shared-decision model leading to individualized therapy plans will be important in patients with VWD undergoing surgical and invasive procedures.
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http://dx.doi.org/10.1182/bloodadvances.2021005666DOI Listing
October 2021

Hospitalization at the end of life in patients with multiple myeloma.

BMC Cancer 2021 Mar 31;21(1):339. Epub 2021 Mar 31.

Department of Hematological Malignancies and Cellular Therapeutics, Kansas University Medical Center, Kansas City, USA.

Background: Despite advances in treatment, multiple myeloma (MM) remains incurable and results in significant morbidity and mortality. Further research investigating where MM patients die and characterization of end-of-life hospitalizations is needed.

Methods: We utilized the National Inpatient Sample (NIS) to explore the hospitalization burden of MM patients at the end of their lives.

Results: The percent of patients dying in the hospital as a percent of overall MM deaths ranged from 54% in 2002 to 41.4% in 2017 (p < 0.01). Blood transfusions were received in 32.7% of these hospitalizations and infections were present in 47.8% of patients. Palliative care and/or hospice consultations ranged from 5.3% in 2002 to 31.4% in 2017 (p < 0.01).

Conclusion: Our study demonstrates that patients with MM dying in the hospital have a significant requirement for blood transfusions and have a high infection burden. We also show that palliative care and hospice involvement at the end of life has increased over time but remains low, and that ultimately, inpatient mortality has decreased over time, but MM patients die in the hospital at a higher rate than the general population.
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http://dx.doi.org/10.1186/s12885-021-08079-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8011131PMC
March 2021

Reconciling LED and monochromator-based measurements of spectral responsivity in solar cells.

Appl Opt 2019 Aug;58(22):6173-6181

Irradiance spectral responsivity is an important measurement characteristic for a solar cell and has served as a primary reference cell calibration parameter for a growing number of national laboratories in recent years. This paper discusses the process by which a packaged reference cell is calibrated using the power spectral responsivity from a monochromator-based measurement coupled with discrete irradiance responsivity measurements from a light-emitting diode (LED) array source to uniformly illuminate the cell. To accurately transfer the responsivity from a calibrated detector cell to a fully packaged reference cell, differences in the measurements of power and irradiance responsivities due to the two separate lighting sources must be reconciled. The spectral effects of using LEDs, as well as other physical packaging effects, are discussed in detail, and a comprehensive treatment of the uncertainty components from both approaches is presented.
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http://dx.doi.org/10.1364/AO.58.006173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839411PMC
August 2019

Epstein-Barr viremia and post-transplant lymphoproliferative disorders in patients undergoing haploidentical stem cell transplantation with post-transplant cyclophosphamide.

Hematol Oncol Stem Cell Ther 2019 Sep 9;12(3):171-173. Epub 2018 Dec 9.

Division of Hematologic Malignancies and Cellular, Therapeutics (HMCT), University of Kansas Medical Center, Kansas City, MO, USA.

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http://dx.doi.org/10.1016/j.hemonc.2018.11.002DOI Listing
September 2019

Utility of Routine Surveillance Imaging for Hodgkin Disease following Autologous Transplant: Experiences from a Single Institution.

Acta Haematol 2018;139(1):52-57. Epub 2018 Jan 17.

Division of Hematologic Malignancies and Cellular Therapeutic (HMCT), University of Kansas Medical Center, Kansas City, KS, USA.

Background: Surveillance scans performed after autologous stem cell transplant (auto-HCT) for patients with Hodgkin disease (HD) have no proven survival benefit.

Methods: We studied survival differences among patients with HD after auto-HCT whose recurrences were detected on clinical history and exam, versus those detected on routine surveillance scan.

Results: Among the 98 patients with HD that underwent auto-HCT from 2000 to 2014 at our institution, 30 relapsed, of which 21 were detected radiologically and 9 clinically. There were no statistically significant differences in patient characteristics between the 2 groups. The median time to progression was 118 days for the clinical cohort and 284 days for the radiological cohort (p = 0.05). Median overall survival (OS) was 728 days for the clinical cohort, and was not reached for the radiological cohort (p = 0.02).

Discussion: In our review, most patients with HD after auto-HCT were diagnosed radiologically. Patients whose relapse was diagnosed clinically were likely to be detected earlier and have a shorter OS. Patients with aggressive disease may be detected when clinically relevant, regardless of scanning. Routine scanning may not be necessary in the majority of patients with HD following auto-HCT.
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http://dx.doi.org/10.1159/000484549DOI Listing
March 2019

Utility of routine surveillance imaging for diffuse large B-cell lymphoma post autologous transplant: A single center experience.

Hematol Oncol Stem Cell Ther 2018 Sep 19;11(3):135-141. Epub 2017 Dec 19.

Division of Hematologic Malignancies and Cellular Therapeutic (HMCT), University of Kansas Medical Center, USA.

Surveillance scans after autologous stem cell transplant (auto-HCT) for patients with relapsed/refractory (RR) diffuse large B Cell lymphoma (DLBCL) have no proven survival benefit. We studied survival differences among patients with RR DLBCL post auto-HCT whose recurrences were detected clinically versus with routine surveillance imaging. Among the 139 patients with RR DLBCL that underwent auto-HCT from 2000 to 2014 at our institution, 37 relapsed: 21 clinical and 16 radiological. The median time to progression was 167 days for the clinical cohort and 565 days for the radiological cohort (p = 0.03), and median overall survival (OS) was 587 days and not reached, respectively (p = 0.006). Most patients with relapsed DLBCL after auto-HCT were diagnosed clinically and were likely to be detected earlier and have a shorter OS. Relapse in patients with aggressive disease will likely be detected when clinically apparent, and the outcome of these patients is independent of the way the relapse is diagnosed. Thus, universal scanning after auto-HCT appears to have little benefit.
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http://dx.doi.org/10.1016/j.hemonc.2017.11.003DOI Listing
September 2018

Spectral dependence of carrier lifetimes in silicon for photovoltaic applications.

J Appl Phys 2016 12 21;120(23). Epub 2016 Dec 21.

Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

Charge carrier lifetimes in photovoltaic-grade silicon wafers were measured by a spectral-dependent, quasi-steady-state photoconductance technique. Narrow bandwidth light emitting diodes (LEDs) were used to excite excess charge carriers within the material, and the effective lifetimes of these carriers were measured as a function of wavelength and intensity. The dependence of the effective lifetime on the excitation wavelength was then analyzed within the context of an analytical model relating effective lifetime to the bulk lifetime and surface recombination velocity of the material. The agreement between the model and the experimental data provides validation for this technique to be used at various stages of the solar cell production line to investigate the quality of the passivation layers and the bulk properties of the material.
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http://dx.doi.org/10.1063/1.4972409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5455797PMC
December 2016

Nonlinearity measurements of solar cells with an LED-based combinatorial flux addition method.

Metrologia 2016 Feb 13;53(1):76-85. Epub 2016 Jan 13.

Intelligent Measurement Systems LLC, Bozeman, MT 59715, USA.

We present a light emitting diode (LED)-based system utilizing a combinatorial flux addition method to investigate the nonlinear relationship in solar cells between the output current of the cell and the incident irradiance level. The magnitude of the light flux is controlled by the supplied currents to two LEDs (or two sets of them) in a combinatorial fashion. The signals measured from the cell are arranged within a related overdetermined linear system of equations derived from an appropriately chosen degree polynomial representing the relationship between the measured signals and the incident fluxes. The flux values and the polynomial coefficients are then solved for by linear least squares to obtain the best fit. The technique can be applied to any solar cell, under either monochromatic or broadband spectrum. For the unscaled solution, no reference detectors or prior calibrations of the light flux are required. However, if at least one calibrated irradiance value is known, then the entire curve can be scaled to an appropriate spectral responsivity value. Using this technique, a large number of data points can be obtained in a relatively short time scale over a large signal range.
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http://dx.doi.org/10.1088/0026-1394/53/1/76DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4977582PMC
February 2016

Large-area irradiance-mode spectral response measurements of solar cells by a light-emitting, diode-based integrating sphere source.

Appl Opt 2014 Jun;53(16):3565-73

An irradiance-mode absolute differential spectral response (SR) measurement system based on a light emitting diode (LED) array is described. The LEDs are coupled to an integrating sphere whose output irradiance is uniform to better than 2% over an area of 160 mm by 160 mm. SR measurements of solar cells when subject to diffuse irradiation, as provided by the integrating sphere, are compared with collimated irradiance SR measurements. Issues originating from the differences in angular response of the reference versus the test cells are also investigated. The SR curves of large-area cells with dimensions of up to 155 mm are measured and then used to calculate the cell's short circuit current (I(sc)), if illuminated by a defined solar spectrum. The resulting values of I(sc) agree well with the values obtained from secondary measurements.
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http://dx.doi.org/10.1364/AO.53.003565DOI Listing
June 2014

Absolute spectral responsivity measurements of solar cells by a hybrid optical technique.

Appl Opt 2013 Jul;52(21):5184-93

Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

An irradiance mode, absolute differential spectral response measurement system for solar cells is presented. The system is based on combining the monochromator-based approach of determining the power mode spectral responsivity of cells with an LED-based measurement to construct a curve representing the light-overfilled absolute spectral response of the entire cell. This curve can be used to predict the short-circuit current (I(sc)) of the cell under the AM 1.5 standard reference spectrum. The measurement system is SI-traceable via detectors with primary calibrations linked to the NIST absolute cryogenic radiometer. An uncertainty analysis of the methodology places the relative uncertainty of the calculated I(sc) at better than ±0.8%.
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http://dx.doi.org/10.1364/AO.52.005184DOI Listing
July 2013

Versatile light-emitting-diode-based spectral response measurement system for photovoltaic device characterization.

Appl Opt 2012 Jul;51(19):4469-76

Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

An absolute differential spectral response measurement system for solar cells is presented. The system couples an array of light emitting diodes with an optical waveguide to provide large area illumination. Two unique yet complementary measurement methods were developed and tested with the same measurement apparatus. Good agreement was observed between the two methods based on testing of a variety of solar cells. The first method is a lock-in technique that can be performed over a broad pulse frequency range. The second method is based on synchronous multifrequency optical excitation and electrical detection. An innovative scheme for providing light bias during each measurement method is discussed.
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http://dx.doi.org/10.1364/AO.51.004469DOI Listing
July 2012
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