bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automated Time-resolved Immunofluorometric Assay for Toxoplasma gondii-specific IgM and IgA Antibodies: Study of More Than 130 000 Filter-Paper Blood-Spot Samples from Newborns
Authors: Sørensen Tina , Spenter Johanne , Jaliashvili Irakli , Christiansen Michael , Nørgaard-Pedersen Bent , Petersen Eskild 
Published: January 2020

Abstract
Background: To screen for congenital toxoplasmosis, we developed a time-resolved immunofluorometric assay for the simultaneous detection of Toxoplasma gondii-specific IgM and IgA in filter-paper samples collected from newborns 4–7 days after birth.
Methods: The assay was performed on the AutoDELFIATM, and results were calculated based on the ToxoM WHO Third International Reference Serum. Comparison with an in-house μ-capture immunoassay was carried out retrospectively on filter-paper samples from children with confirmed congenital toxoplasmosis. Prospectively the assay was compared with a μ-capture immunoassay on 68 394 samples and a commercially available assay on another 69 467 samples. Before serum was requested from the newborn, positive samples were tested for IgA and IgM separately and in an IgM-immunosorbent agglutination assay developed for filter-paper samples.
Results: Intra- and interassay variations (CVs) were 8% and 16%, respectively. The cutoff of 5 units/mL produced a 0.5% retest rate. The assay detected 13 of 18 (72%) samples from newborns diagnosed with congenital toxoplasmosis in the retrospective study. Prospectively, the assay identified 24 newborns who were later diagnosed with congenital toxoplasmosis. Results for all 24 cases were positive by the respective comparison method. No cases were detected solely by the IgA antibodies in the sample.
Conclusion: Neonatal screening for congenital toxoplasmosis can be automated by use of purified europium-labeled antigen for detection of T. gondii-specific IgM and IgA eluted from filter-paper samples.
Genotyping of Essential Hypertension Single-Nucleotide Polymorphisms by a Homogeneous PCR Method with Universal Energy Transfer Primers
Authors: Bengra Chikh , Mifflin Theodore E , Khripin Yuri , Manunta Paolo , Williams Scott M , Jose Pedro A , Felder Robin A 
Published: January 2020

AbstractBackground: Human hypertension is a complex, multifactorial disease with a heritability of more than 30–50%. A genetic screening test based on analysis of multiple single-nucleotide polymorphisms (SNPs) to assess the likelihood of developing hypertension would be helpful for disease management.Methods: Tailed allele-specific primers were designed to amplify by PCR six biallelic SNP loci [three in G protein-coupled receptor kinase type 4 (GRK4): R65L, A142V, and A486V; two in angiotensinogen: −6G→A and M235T; and one in aldosterone synthase: −344C→T] associated with essential hypertension. PCRs of SNP loci were coupled (via a common sequence of 21 nucleotide tails) to incorporate Universal Amplifluor™ primers labeled with fluorescein or sulforhodamine in a homogeneous format. Use of Amplifluors in SNP PCRs produced labeled amplicons, the fluorescence of which was quantified by a microplate reader and then analyzed via an Excel macro to provide genotypes for all six SNP loci. Unique restriction endonucleases were identified for five SNP loci that could independently confirm homogeneous PCR results when needed.Results: We developed six homogeneous PCR assays that were set up, performed, and fluorometrically analyzed in 96-well microplates. Allele frequencies were determined for six SNPs in 60 Italian hypertensive patients and a control group of 60 normotensive persons. A significant correlation (P = 0.034) between one SNP [GRK4 (A486V)] and the hypertensive patients was observed. Genotyping results for five of six SNPs were confirmed by digesting corresponding amplicons with locus-specific restriction endonucleases.Conclusions: We developed a simple and homogeneous fluorescent protocol that has been used to determine the SNP genotype for six loci in a population of hypertensive and normotensive persons. We also observed a significant association (P = 0.034) between one SNP (A486V) and an Italian population of mildly hypertensive patients.
Serum Paraoxonase Activity: A New Additional Test for the Improved Evaluation of Chronic Liver Damage
Authors: Ferré Natàlia , Camps Jordi , Prats Eduard , Vilella Elisabet , Paul Antoni , Figuera Lídia , Joven Jorge 
Published: January 2020

AbstractBackground: Paraoxonase 1 (PON1) is an ester hydrolase present in serum and in the liver. The aims of the present study were to investigate the following: (a) the relationship between serum PON1 activity alterations and the degree of liver damage in patients with chronic liver disease; (b) the influence of genetic variability on serum PON1 activity; and (c) the efficacy of serum PON1 activity measurement, alone and in combination with standard liver function tests, in the assessment of liver damage.Methods: We studied 68 patients with liver cirrhosis, 107 patients with chronic hepatitis, and 368 apparently healthy volunteers. Baseline and salt-stimulated PON1 activities were measured by the hydrolysis of paraoxon. PON1 genotyping at positions 55 and 192 was analyzed by PCR and restriction isotyping.Results: Baseline and stimulated PON1 activities were decreased (P &lt;0.001) in chronic hepatitis and in liver cirrhosis. PON1 activity was significantly correlated with serum total proteins, albumin, and bilirubin in patients but not in controls. There were no significant differences with respect to allele and genotype frequencies between patients and controls. The combination of baseline serum PON1 with five standard biochemical tests had a higher classification accuracy (94% of patients; 96% of controls) than the five standard tests alone (75% of patients; 96% of controls). ROC plots demonstrated a high diagnostic accuracy for baseline serum PON1 [area under the curve, 0.89 (95% confidence interval, 0.86–0.93) in chronic hepatitis and 0.96 (95% confidence interval, 0.94–0.99) in cirrhosis]. Baseline PON1 provided the highest ROC area for cirrhosis vs controls.Conclusions: The significant decrease of PON1 activity in chronic liver diseases is related to the degree of hepatic dysfunction and not to allelic or genotypic differences. Addition of serum PON1 activity measurement to the current battery of tests may improve the evaluation of chronic liver diseases.
Bleomycin-detectable Iron Assay for Non-Transferrin-bound Iron in Hematologic Malignancies
Authors: von Bonsdorff Leni , Lindeberg Enni , Sahlstedt Leila , Lehto Jari , Parkkinen Jaakko 
Published: January 2020

AbstractBackground: A microwell modification of the bleomycin assay for determining non-transferrin-bound iron (NTBI) was evaluated and compared with a chelation method.Methods: The bleomycin assay reagent and sample volumes were halved, and measurements were done in microwell plates. Samples from patients treated for hematologic malignancies were studied. The chelation method was based on mobilization of NTBI with a chelator and measurement of the ultrafiltered iron-chelator complex. NTBI results were also compared with transferrin saturation and the distribution of transferrin iron forms by urea-polyacrylamide gel electrophoresis.Results: The bleomycin assay intraassay imprecision (CV) was 7.7% and 8.2% and the interassay imprecision was 18% and 9.8% for a low (0.2 μmol/L) and a high (1.5 μmol/L) control, respectively. Hemolysis increased measured NTBI. A detection limit of 0.1 μmol/L was established based on the interference of nonvisible hemolysis and on accuracy studies. In patient samples, NTBI exceeded the detection limits only when transferrin saturation was &gt;80%. Compared with the chelation method, the bleomycin assay gave clearly lower NTBI concentrations. The chelation method also gave positive results at &lt;80% transferrin saturation. The recovery of iron added as ferric nitrilotriacetate to serum was 33% by the bleomycin assay and 64% by the chelation assay.Conclusions: The microwell version of the bleomycin assay is reproducible. When hemolyzed samples were excluded, bleomycin-detectable iron was found only when the transferrin saturation was &gt;80%, suggesting high specificity. Bleomycin-detectable iron constitutes only a portion of the NTBI measured by the chelation method.
Predominant Hematopoietic Origin of Cell-free DNA in Plasma and Serum after Sex-mismatched Bone Marrow Transplantation
Authors: Lui Yanni YN , Chik Ki-Wai , Chiu Rossa WK , Ho Cheong-Yip , Lam Christopher WK , Lo YM Dennis 
Published: January 2020

Abstract
Background: Despite current interest in the biology and diagnostic applications of cell-free DNA in plasma and serum, the cellular origin of this DNA is poorly understood. We used a sex-mismatched bone marrow transplantation model to study the relative contribution of hematopoietic and nonhematopoietic cells to circulating DNA.
Methods: We studied 22 sex-mismatched bone marrow transplantation patients. Paired buffy coat and plasma samples were obtained from all 22 patients. Matching serum samples were also obtained from seven of them. Plasma DNA, serum DNA, and buffy coat were quantified by real-time PCR of the SRY and β-globin gene DNA. To investigate the effects of blood drawing and other preanalytical variables on plasma DNA concentrations, blood samples were also collected from 14 individuals who had not received transplants. The effects of blood sampling by syringe and needle, centrifugation, and time delay in blood processing were studied.
Results: The median percentage of Y-chromosome DNA in the plasma in female patients receiving bone marrow from male donors (59.5%) differed significantly (P &lt;0.001) from that in the male patients receiving bone marrow from female donors (6.9%). This indicated that plasma DNA in the bone marrow transplantation recipients was predominantly of donor origin. Compared with paired plasma samples, serum samples had a median 14-fold higher DNA concentration, with the additional DNA being of donor origin. Control experiments indicated that none of the three tested preanalytical variables contributed to a significant change in cell-free DNA concentration.
Conclusions: After bone marrow transplantation, the DNA in plasma and serum is predominantly hematopoietic in origin. Apart from the biological implications of this observation, this finding suggests that plasma and serum can be used as alternative materials for the study of postbone marrow transplantation chimerism.
Comparison of the Emit Immunoassay with HPLC for Therapeutic Drug Monitoring of Mycophenolic Acid in Pediatric Renal-Transplant Recipients on Mycophenolate Mofetil Therapy
Authors: Weber Lutz T , Shipkova Maria , Armstrong Victor W , Wagner Natalie , Schütz Ekkehard , Mehls Otto , Zimmerhackl Lothar B , Oellerich Michael , Tönshoff Burkhard 
Published: January 2020

AbstractBackground: HPLC is currently the preferred method for accurate measurement of mycophenolic acid (MPA). This study was designed to validate the Emit compared with HPLC in relation to clinical outcome measurements.Methods: Pediatric renal-transplant recipients (n = 50) on an immunosuppressive triple regimen consisting of cyclosporin A, prednisone, and mycophenolate mofetil (600 mg/m2 twice per day) were investigated in an open-label prospective study. Pharmacokinetic profiles over 12 h were obtained at 1 week, 3 weeks, 3 months, and 6 months posttransplant. Plasma MPA was measured by both reversed-phase HPLC and the Emit immunoassay.Results: There was an association between the risk of acute rejection episodes and low area under the curve values from t0 to t12h (AUC0–12) for MPA (MPA-AUC0–12) or predose concentrations of MPA derived from both HPLC and Emit measurements. According to ROC analysis, an AUC value of 33.8 mg · h/L for MPA from t0 to t12h (MPA-AUC0–12) determined by HPLC had a diagnostic sensitivity of 80% and a diagnostic specificity of 57%. The corresponding value of the Emit was 36.1 mg · h/L. For the predose concentration (MPA-c12), a concentration of 1.2 mg/L determined by HPLC and 1.4 mg/L determined by Emit gave a sensitivity of 80% and a specificity of 60%, respectively. There was no association of any pharmacokinetic variables derived from total MPA measurements with an increased risk of side effects related to mycophenolate mofetil.Conclusions: The Emit assay appears to have a comparable diagnostic efficacy to HPLC for assessing the risk of acute rejection in pediatric renal-transplant recipients. However, because of the cross-reactivity of the antibody used in the Emit assay with the active MPA acyl glucuronide metabolite, the decision thresholds for the Emit were higher than those calculated from HPLC measurements.
The Tortuous Road to the Adoption of katal for the Expression of Catalytic Activity by the General Conference on Weights and Measures
Authors: Dybkær René 
Published: January 2020

Abstract
Background: The “unit” for “enzymic activity” (U = 1 μmol/min) was recommended by the International Union of Biochemistry and Molecular Biology (IUB) in 1961 and is widely used in medical laboratory reports. The general trend in metrology, however, is toward global standardization through defining units coherent with the International System of Units (SI).
Approach: Several proposals were advanced from the IFCC, International Union of Pure and Applied Chemistry, and IUB regarding the definition for enzymic activity as well as the terms for kind-of-quantity, units, symbol, and dimension. In 1977, international agreement was reached between these bodies and WHO that “catalytic activity” (z), of a catalyst in a given system is defined by the rate of conversion in a measuring system (in mol/s) and expressed in “katal” (symbol, kat; equal to 1 mol/s). The katal is invariant of the measurement procedure, but the numerical quantity value is not. Gaining support for the katal from the final arbiter, the General Conference on Weights and Measures, was slow, but Resolution 12 of 1999 adopted the katal (symbol, kat) as a special name and symbol for the SI-derived unit, mol/s, used in measuring catalytic activity.
Conclusions: Laboratory results for amounts of catalysts, including enzymes, measured by their catalytic activity can now officially be expressed in katals and are traceable to the SI provided that the specified indicator reaction reflects first-order kinetics. The conversion from “unit” is: 1 U = 16.667 × 10−9 kat. Further derived quantities have coherent units such as kat/L, kat/kg, and kat/kat = 1.
Detection of Epitestosterone Doping by Isotope Ratio Mass Spectrometry
Authors: Aguilera Rodrigo , Hatton Caroline K , Catlin Don H 
Published: January 2020

AbstractBackground: Epitestosterone is prohibited by sport authorities because its administration will lower the urinary testosterone/epitestosterone ratio, a marker of testosterone administration. A definitive method for detecting epitestosterone administration is needed.Methods: We developed a gas chromatography-combustion-isotope ratio mass spectrometry method for measuring the δ13C values for urinary epitestosterone. Sample preparation included deconjugation with β-glucuronidase, solid-phase extraction, and semipreparative HPLC. Epitestosterone concentrations were determined by gas chromatography-mass spectrometry for urines obtained from a control group of 456 healthy males. Epitestosterone δ13C values were determined for 43 control urines with epitestosterone concentrations ≥40 μg/L (139 nmol/L) and 10 athletes’ urines with epitestosterone concentrations ≥180 μg/L (624 nmol/L), respectively.Results: The log epitestosterone concentration distribution was gaussian [mean, 3.30; SD, 0.706; geometric mean, 27.0 μg/L (93.6 nmol/L)]. The δ13C values for four synthetic epitestosterones were low (less than or equal to −30.3‰) and differed significantly (P &lt;0.0001). The SDs of between-assay precision studies were low (≤0.73‰). The mean δ13C values for urine samples obtained from 43 healthy males was −23.8‰ (SD, 0.93‰). Nine of 10 athletes’ urine samples with epitestosterone concentrations &gt;180 μg/L (624 nmol/L) had δ13C values within ± 3 SD of the control group. The δ13C value of epitestosterone in one sample was −32.6‰ (z-score, 9.4), suggesting that epitestosterone was administered. In addition, the likelihood of simultaneous testosterone administration was supported by low δ13C values for androsterone and etiocholanolone.Conclusions: Determining δ13C values for urinary epitestosterone is useful for detecting cases of epitestosterone administration because the mean δ13C values for a control group is high (−23.8‰) compared with the δ13C values for synthetic epitestosterones.
Multicenter Evaluation of an Automated Assay for Troponin I
Authors: Uettwiller-Geiger Denise , Wu Alan HB , Apple Fred S , Jevans Anthony W , Venge Per , Olson Marilyn D , Darte Claude , Woodrum David L , Roberts Sean , Chan Stephen 
Published: January 2020

AbstractBackground: Cardiac troponin I (cTnI) is a powerful tool to aid in the diagnosis of myocardial infarction and cardiac muscle damage. We describe an assay that overcomes problems of early assays that were often affected by cTnI degradation, assay interference, poor sensitivity, and imprecision.Methods: The analytical performance of the Access® AccuTnITM assay (Beckman Coulter) was evaluated at five institutions. Controls, zero calibrator, and diluted patient samples were used to determine precision, detection limit, functional sensitivity, and linearity. The 97.5 and 99 percentiles of a reference population were determined. Common interferents and heterophilic patient samples were tested. Equimolarity was determined by assaying samples with various ratios of free and complexed cTnI. Matched samples drawn into serum, EDTA, lithium heparin, and sodium heparin sample tubes were compared.Results: Total imprecision (CVs) was 4.0–8.8% between 0.40 and 31 μg/L cTnI. The detection limit was &lt;0.01 μg/L. The 97.5 percentile upper reference limit (URL) was 0.03 μg/L (CV = 20%), and the 99 percentile URL was 0.04 μg/L (CV = 14%). Total CVs of 10% and 20% were seen at and above 0.06 and 0.03 μg/L, respectively. The assay was linear to &gt;60 μg/L and not affected by common assay interferents. An equimolar response was observed with free, complexed, phosphorylated, and dephosphorylated forms of cTnI. Results were 4% lower in serum and 14% lower in EDTA plasma than in lithium heparin plasma (P &lt;0.01), independent of cTnI concentration.Conclusion: AccuTnI is a sensitive and precise assay for the measurement of cTnI.
Setting Performance Goals and Evaluating Total Analytical Error for Diagnostic Assays
Authors: Krouwer Jan S 
Published: January 2020

AbstractBackground: Total analytical error has been a useful metric both to assess laboratory assay quality and to set goals. It is often estimated by combining imprecision (SD) and average bias in the equation: total analytical error = bias + 1.65 × imprecision. This indirect estimation model (referred to as the simple combination model) leads to different estimates of total analytical error than that of a direct estimation method (referred to as the distribution-of-differences method) or of simulation.Methods: A review of the literature was undertaken to reconcile the different estimation approaches.Results: The simple combination model can underestimate total analytical error by neglecting random interference bias and by not properly treating other error sources such as linear drift and outliers. A simulation method to estimate total analytical error is outlined, based on the estimation and combination of total analytical error source distributions. Goals for each total analytical error source can be established by allocation of the total analytical error goal. Typically, the allocation is cost-based and uses the probability of combinations of error sources. The distribution-of-differences method, simple combination model, and simulation method to evaluate total analytical error are compared. Outlier results can profoundly influence quality, but their rates are seldom reported.Conclusions: Total analytical error should be estimated either directly by the distribution-of-differences method or by simulation. A systems engineering approach that uses allocation of the total analytical error goal into error source goals provides a cost-effective approach to meeting total analytical error. Because outliers can cause serious laboratory error, the inclusion of outlier rate estimates from large studies (e.g., those conducted by manufacturers) would be helpful in assessing assay quality.
Longitudinal Concentrations of Vitamin B12 and Vitamin B12-binding Proteins during Uncomplicated Pregnancy
Authors: Koebnick Corinna , Heins Ulrike A , Dagnelie Pieter C , Wickramasinghe Sunitha N , Ratnayaka Indrika D , Hothorn Torsten , Pfahlberg Annette B , Hoffmann Ingrid , Lindemans Jan , Leitzmann Claus 
Published: January 2020

AbstractBackground: Because reference values for vitamin B12 concentrations and vitamin B12-binding capacities for pregnant women have not been established, the reference values for nonpregnant women are often applied to assess vitamin B12 status. The aim of the present study was to describe ranges of biochemical indices of vitamin B12 status, including red blood cell (RBC) vitamin B12, saturated and unsaturated cobalamin-binding proteins, and binding capacities in all trimesters of uncomplicated pregnancy.Methods: A total of 39 healthy pregnant women with long-term daily intake of vitamin B12 &gt;2.6 μg/day and uncomplicated pregnancies participated in the study throughout their pregnancies. RBCs and serum vitamin B12, holo-haptocorrin, unsaturated cobalamin-binding proteins, unsaturated and total vitamin B12-binding capacities, total homocysteine (tHcy), and RBC count were assessed in weeks 9–12, 20–22, and 36–38 of gestation.Results: Significant changes in vitamin B12 status occurred in the course of pregnancy. Serum vitamin B12 concentrations and percentage of saturation of vitamin B12-binding proteins decreased steadily throughout pregnancy. In the third trimester, 35% of the participants had serum vitamin B12 concentrations &lt;150 pmol/L and 68.6% had &lt;15% saturation of total vitamin B12-binding capacities, but no women had RBC vitamin B12 concentrations &lt;148 pmol/L. However, the decrease in these indices was not associated with reduced hemoglobin concentrations or RBC count or with increased tHcy concentrations.Conclusions: Our findings suggest that the reference values for vitamin B12 status in nonpregnant women may not be applicable to pregnant women.