bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantifying the bias associated with use of discrepant analysis
Authors: Lipman Harvey B , Astles J Rex 
Published: January 2020

AbstractDiscrepant analysis is a widely used technique for estimating the performance parameters of a laboratory test. In discrepant analysis, each specimen is initially tested with the candidate test and a comparison method, and when the results of the two tests disagree, a confirmatory test is used to resolve the discrepancy. Discrepant analysis usually produces biased estimates. This report quantifies this bias and shows that it is usually positive, leading to overestimation of the performance parameters of a laboratory test. The direction and magnitude of the bias are predictably influenced by the analytical sensitivity and specificity of the candidate test, comparison method, and confirmatory test. The proportion of abnormal specimens tested also affects the magnitude of the bias, particularly the estimates of analytical sensitivity and positive predictive value when this proportion is low. Alternative approaches are suggested.
Mechanisms of dopamine and dobutamine interference in biochemical tests that use peroxide and peroxidase to generate chromophore
Authors: Karon Brad S , Daly Thomas M , Scott Mitchell G 
Published: January 2020

Abstract
Dopamine and dobutamine have recently been shown to produce a negative interference in several biochemical tests that use peroxide and peroxidase to generate a chromophore. To define the chemical mechanism of this interference, we examined the effects of dopamine and dobutamine in various peroxidase-based biochemical tests. Dopamine interfered stoichiometrically with peroxidase-based tests that use 4-aminophenazone to form chromophore but interfered little in those that use other compounds to generate chromophore. Dopamine reacts with 4-aminophenazone in the presence of peroxide and peroxidase to form a novel quinone-imine dye, with a smaller absorptivity than the chromophore formed in the absence of dopamine. The smaller absorptivity of this novel chromophore results in negative interference by reducing the total absorbance at the wavelength used to measure analyte. In contrast, dobutamine interfered stoichiometrically with all peroxidase-based tests studied, regardless of whether 4-aminophenazone was used to form the chromophore. Dobutamine was rapidly oxidized by peroxide in the presence of peroxidase, thus depleting the peroxide necessary to generate chromophore. Dopamine and dobutamine demonstrate two distinct general mechanisms of interference in peroxidase-based biochemical tests.
Cardiac troponin I measurement with the ACCESS® immunoassay system: analytical and clinical performance characteristics
Authors: Christenson Robert H , Apple Fred S , Morgan David L , Alonsozana Gladys L , Mascotti Kristin , Olson Marilyn , McCormack Robert T , Wians Frank H , Keffer Joseph H , Duh Show-Hong 
Published: January 2020

AbstractWe evaluated the ACCESS® cardiac troponin I (cTnI) immunoassay as a marker for myocardial infarction (MI). Total imprecision was 6.0% to 13.5%, the minimum detectable concentration was 0.007 μg/L, and the limit of quantitation was 0.046 μg/L. Comparison of cTnI measurement between the ACCESS and Stratus systems (n = 114) showed a proportional difference: ACCESS cTnI = 0.0996 Stratus cTnI + 0.049 μg/L (r = 0.811). Fifty-nine of 61 ambulatory patients without cardiac symptoms had no detectable cTnI (95% range, 0.00 to 0.025 μg/L). The optimum cutoff for discriminating MI (n = 289, 45 with MI) was 0.15 μg/L by receiver operator characteristic curve analysis; at this cutoff, the ACCESS cTnI assay showed a sensitivity of 88.9% (95% CI, 79.7–98.1%) and specificity of 91.8% (95% CI, 88.4–95.2%). The ACCESS cTnI assay results showed 89.4% and 93.0% concordance with the MB isoenzyme of creatine kinase (CK-MB) mass and Stratus cTnI results, respectively, for classification of patients with suspected MI. The ACCESS cTnI assay appears to show sensitivity and specificity comparable with those of both CK-MB mass and Stratus cTnI assays for the diagnosis of MI in patients presenting within 12 h of onset of symptoms.
Molecular diagnosis of medium-chain acyl-CoA dehydrogenase deficiency by oligonucleotide ligation assay
Authors: Romppanen Eeva-Liisa , Mononen Tarja , Mononen Ilkka 
Published: January 2020

Abstract
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a recessively inherited defect in the mitochondrial β-oxidation of fatty acids. A single nucleotide change, the A985→G transition, in the MCAD gene accounts for ∼90% of all the disease-causing mutations in the patients. We have used PCR to amplify a segment of the human MCAD gene and typed the allelic sequence variation at base 985 by a colorimetric oligonucleotide ligation assay (OLA). PCR/OLA provides a technique that permits differentiation of the homozygotes, heterozygotes, and normals for the A985→G allele in the MCAD gene. Genotyping of 1908 random Finnish DNA samples by OLA identified 10 carriers of the mutant allele, but no homozygotes were found. The calculated carrier frequency for the A985→G mutation was 1:191 (95% confidence limits, 1:118–1:501), and the calculated frequency for the A985→G homozygotes was 1:147 000 (95% confidence limits, 1:56 000–1:1 004 000).
Plasma concentration, kinetic constants, and gene polymorphism of angiotensin I-converting enzyme in centenarians
Authors: Faure-Delanef Laurence , Baudin Bruno , Bénéteau-Burnat Bénédicte , Beaudoin Jean-Christophe , Giboudeau Jacqueline , Cohen Daniel 
Published: January 2020

Abstract
We have determined serum activity and kinetic constants of angiotensin I-converting enzyme (ACE), parallel to an insertion/deletion (I/D) polymorphism in its gene, in French centenarians and controls 20–70 years of age because this enzyme could have an impact on cardiovascular risk, and thus on longevity. Both the ACE D allele and ACE D/D genotype were more frequent in centenarians in comparison with controls, without sex-related differences nor significant correlation with a cardiovascular pathology. In centenarians, I/D polymorphism was correlated with circulating ACE activity (D/D genotype, 89.0 ± 36.8 U/L; I/D genotype, 63.5 ± 26.0 U/L; and I/I genotype, 55.1 ± 39.4 U/L). The Michaelis constants for two substrates were identical whatever the genotype and were not different between centenarians and controls, i.e., 0.30 ± 0.03 mmol/L for furylacryloyl-phenylalanyl-glycyl-glycine and 1.35 ± 0.05 mmol/L for hippuryl-histidyl-leucine; for the latter, the optimal pH and activating concentration of chloride did not depend on I/D polymorphism. The maximal velocities with both substrates reflected the distribution of serum ACE activity as a function of the genotypes, in centenarians and in controls. In conclusion, plasma ACE activity is subject to a similar genotypic influence in centenarians as in adults 20–70 years of age; however, ACE itself appears to be functionally similar for each genotype. Furthermore, the D allele as well as the higher serum ACE activities associated with the D/D genotype cannot discriminate individuals at high risk for cardiovascular diseases, major causes of mortality before the age of 100 years.
New sensitive method for the detection of the A3243G mutation of human mitochondrial deoxyribonucleic acid in diabetes mellitus patients by ligation-mediated polymerase chain reaction
Authors: Urata Michiyo , Wakiyama Machiko , Iwase Masanori , Yoneda Makoto , Kinoshita Sachiko , Hamasaki Naotaka , Kang Dongchon 
Published: January 2020

Abstract
An adenine-to-guanine mutation at nucleotide position (np) 3243 in the mitochondrial tRNALeu(UUR) gene is closely associated with various clinical phenotypes of diabetes mellitus. Because the mutation creates a new restriction site for the restriction enzyme ApaI, the mutation is usually detected and quantified by ApaI cleavage of the PCR products including np 3243. The sensitivity of the conventional method is, however, 5–10% heteroplasmy. The percentage of heteroplasmy of the mutation is usually highest in the affected tissues and is much lower in peripheral blood cells, which are used most frequently for the analysis. The sensitivity of the conventional method, however, is not sufficient to detect the mutation from peripheral blood cells. Utilizing ligation-mediated polymerase chain reaction, we have developed a feasible and sensitive method to detect 0.01% heteroplasmy of the 3243 mutation in peripheral leukocytes.
K-ras mutations in stools and tissue samples from patients with malignant and nonmalignant pancreatic diseases
Authors: Berndt Christoph , Haubold Katrin , Wenger Frank , Brux Brigitte , Müller Joachim , Bendzko Peter , Hillebrand Timo , Köttgen Eckhard , Zanow Jürgen 
Published: January 2020

Abstract
Mutant-enriched PCR and reverse dot blot hybridization in microplates were applied for examining K-ras status in stools and tissue samples from patients with pancreatic tumors and chronic pancreatitis. In tissue samples, K-ras mutations were found in 32 of 35 cases of ductal adenocarcinoma, in 5 of 7 periampullary cancers, in 1 cystadenocarcinoma, and in 3 of 5 patients with chronic pancreatitis. In stools, mutated K-ras was seen in 10 of 25 cases of ductal adenocarcinoma, in 1 case of cystadenocarcinoma, and in 2 of 6 cases of chronic pancreatitis. These data indicate that the K-ras status of stool samples may help identify pancreatic carcinoma and persons at risk for cancer development; however, it does not allow discrimination of malignant from nonmalignant diseases.
Measurement of LDL particle size in whole plasma and serum by high performance gel-filtration chromatography using a fluorescent lipid probe
Authors: Scheffer Peter G , Bakker Stephan J L , Heine Robert J , Teerlink Tom 
Published: January 2020

AbstractWe have recently described a technique for measuring LDL size by high performance gel-filtration chromatography (HPGC) with UV detection (Scheffer et al., Clin Chem 1997;43:1904–12). A drawback of this method is the necessity of LDL isolation before chromatography. We now describe a modification of this method based on selective detection of lipoproteins by postcolumn labeling with parinaric acid, a fluorescent lipid probe. Measuring the size of isolated LDL by HPGC in 56 subjects, we obtained diameters of 25.72 ± 0.60 nm with UV detection and of 25.74 ± 0.58 nm with fluorescence detection. The modified method is suitable for LDL size measurement in whole plasma or serum. LDL sizes measured in whole plasma correlated strongly with the respective values in isolated LDL (r = 0.976) but were on average 0.18 nm larger (P &lt; 0.001). CVs for within- and between-series imprecision were &lt;0.25%. The present method requires only 5 μL plasma or serum without sample preparation and is suitable for the unattended analysis of large series of samples.
Enzyme immunoassay of urinary mevalonic acid and its clinical application
Authors: Hiramatsu Makoto , Hayashi Akio , Hidaka Hideki , Ueshima Hirotsugu , Kanno Takashi 
Published: January 2020

AbstractWe have developed an enzyme immunoassay for mevalonic acid (MVA), using a specific monoclonal antibody. The intra- and interassay coefficients of variation calculated on two urine samples were 3.3% and 3.4%, respectively, in the intraassay precision test and 3.5% and 6.9% in the interassay evaluation. Pravastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, was administered to nine healthy men, and in all cases, their MVA excretion rates then decreased. The more MVA that was excreted in the urine before the pravastatin administration, the greater a reduction of MVA excretion was observed. The daily MVA excretions in healthy men (n = 120) and women (n = 105) were 2.32 μmol/day (SD, 0.82 μmol/day) and 1.85 μmol/day (SD, 0.47 μmol/day), respectively. In streptozotocin-induced diabetic rats (n = 14), the plasma cholesterol concentrations and MVA excretion rates were increased, and a positive correlation was observed between the plasma cholesterol and the urinary MVA concentrations.
K-ras gene mutations in the diagnosis of fine-needle aspirates of pancreatic masses: prospective study using two techniques with different detection limits
Authors: Mora Josefina , Puig Pere , Boadas Jaume , Urgell Eulàlia , Montserrat Enric , Lerma Enrique , González-Sastre Francesc , Lluís Fèlix , Farré Antoni , Capellá Gabriel 
Published: January 2020

Abstract
Detection of K-ras mutations may be useful in the evaluation of pancreatic cancer. The aim of this study was to assess, in a prospective design, the diagnostic utility of K-ras mutation analysis in 62 consecutive fine-needle aspirates of pancreatic masses, using two PCR-based techniques—standard and enriched—with detection limits of a mutant allele in the presence of 102 or 103 wild-type alleles, respectively. Cytology alone offered a diagnostic sensitivity of 75%. The enriched higher sensitivity detection technique, in combination with cytology, offered a diagnostic sensitivity of 91% without false positives. The molecular analysis would have contributed to diagnosis in an additional 14 cases of pancreatic cancer. The standard technique contributed to diagnosis in an additional 9 cases. These results strongly support the use of the enriched method of detecting K-ras mutations as a complement to cytology in the evaluation of pancreatic masses.
Cardiac troponin I and minor cardiac damage: biochemical markers in a clinical model of myocardial lesions
Authors: Manuel del Rey José , Madrid Antonio Hernández , Valiño José Manuel , Rubí José , Mercader José , Moro Concepción , Ripoll Eduardo 
Published: January 2020

AbstractRadiofrequency (RF) catheter ablation is the curative treatment of choice for many cardiac arrhythmias. After RF ablation there is always a small localized endomyocardial necrosis, necessary to abolish the arrhythmia. We designed this study to determine the serum concentrations of several cardiac markers in patients who underwent RF catheter ablation. The study shows a higher frequency of increase of serum cardiac troponin I (cTnI) than of creatine kinase (CK), the CK MB isoenzyme (CK-MB), or myoglobin. A pathological value of cTnI was found in 47 of 51 patients (92%) in the ablation group. The area under the ROC curve for cTnI was 0.9375, significantly higher than for the other biochemical markers (0.86, 0.76, and 0.75 for CK-MB, myoglobin, and CK, respectively), with P &lt;0.05. We conclude that the serum concentration of cTnI is the best biochemical marker for detecting the minor myocardial damage produced by RF ablation.
Correlation between total homocysteine and cyclosporine concentrations in cardiac transplant recipients
Authors: Cole David EC , Ross Heather J , Evrovski Jovan , Langman Loralie J , Miner Steven ES , Daly Paul A , Wong Pui-Yuen 
Published: January 2020

Abstract
Increased circulating total homocysteine (tHcy) has been implicated as an independent risk factor for atherosclerotic disease. In cardiac transplant patients, accelerated coronary atherosclerosis is an important cause of late allograft failure; however, studies of tHcy in this at-risk group are limited. We sampled a cohort of 72 subjects 3.95 ± 3.14 (mean ± SD) years after transplantation and found that all had tHcy concentrations above our upper reference limit (15.0 μmol/L). The mean tHcy in the transplant group (25.4 ± 7.1 μmol/L) was significantly greater than in our reference group (9.0 ± 4.3 μmol/L; n = 457; P &lt;0.001). We also examined the effect of age, gender, time since transplant, serum folate and cobalamin, total protein, urate, creatinine, albumin, and trough whole blood cyclosporine concentrations. In a multiple linear regression model, only creatinine (mean 144 ± 52 μmol/L; P = 0.021) and trough cyclosporine concentrations (191 ± 163 μg/L; P = 0.015) were independent positive predictors of tHcy, whereas serum folate (8.35 ± 7.43 nmol/L; P = 0.018) and time since transplant (P = 0.049) were significant negative predictors. We conclude that hyperhomocysteinemia is a common characteristic of cardiac transplant recipients. Our analysis suggests that folate and renal glomerular dysfunction are important contributory factors; however, whole blood cyclosporine concentrations may also predict the degree of hyperhomocysteinemia in this population and therefore influence interpretation of any apparent response to treatment.
Automated measurement of serum ferroxidase activity
Authors: Erel Ozcan 
Published: January 2020

Abstract
A method is described for automated measurement of serum ceruloplasmin ferroxidase activity. In this method, Fe2+ ions are used as the substrate. In addition, a new calibration system without ceruloplasmin is also presented. Optimum assay reaction conditions were determined. Maximal catalytic activity was obtained at 0.45 mol/L acetate buffer, pH 5.8. The reagents and calibrator are stable for at least 6 months. Significant correlations between serum ferroxidase and p-phenylenediamine oxidase activities (r = 0.96; P &lt;0.0001) and copper concentration (r = 0.93; P &lt;0.0001) were found. The range for serum ceruloplasmin ferroxidase activity in healthy persons was 198-1107 U/L, and in patients with bronchial asthma it was 601-1912 U/L.
Lyophilized bovine hemoglobin as a possible reference material for the determination of hemoglobin derivatives in human blood
Authors: Maas Bart H A , Buursma Anneke , Ernst Rob A J , Maas Anton H J , Zijlstra Willem G 
Published: January 2020

Abstract
We investigated the suitability of a lyophilized bovine hemoglobin (LBH) preparation containing various fractions of oxyhemoglobin (O2Hb), carboxyhemoglobin (COHb), and methemoglobin (MetHb) for quality assessment in multicomponent analysis (MCA) of hemoglobin derivatives. It was demonstrated that a stable preparation of these components after reconstitution yields a hemoglobin solution that is spectrophotometrically equivalent with a fresh bovine hemoglobin solution. The preparation was found to be stable for at least 1 year when it is kept at 2–8 °C and for 1 h after reconstitution. We determined the fractions of O2Hb, COHb, and MetHb of several LBH preparations, using the complete spectra of 480–650 nm with 2-nm intervals and absorptivities as determined for pure LBH solutions. A field trial involving various types of multiwavelength hemoglobin photometers showed the suitability of LBH as a quality-control material. Computer models of the various common multiwavelength hemoglobin photometers may be useful for establishing more accurate target values of LBH preparations for each type of photometer and for studying the importance of the influence of specific factors such as wavelength selection, absorptivity values, and interfering dyes.
Degradation of cardiac troponin I: implication for reliable immunodetection
Authors: Katrukha Aleksei G , Bereznikova Anastasia V , Filatov Vladimir L , Esakova Tatiana V , Kolosova Olga V , Pettersson Kim , Lövgren Timo , Bulargina Tamara V , Trifonov Igor R , Gratsiansky Nikolai A , Pulkki Kari , Voipio-Pulkki Liisa-Maria , Gusev Nikolai B 
Published: January 2020

AbstractWe have analyzed by different immunological methods the proteolytic degradation of cardiac troponin I (cTnI) in human necrotic tissue and in serum. cTnI is susceptible to proteolysis, and its degradation leads to the appearance of a wide diversity of proteolytic peptides with different stabilities. N- and C-terminal regions were rapidly cleaved by proteases, whereas the fragment located between residues 30 and 110 demonstrated substantially higher stability, possibly because of its protection by TnC. We conclude that antibodies selected for cTnI sandwich immunoassays should preferentially recognize epitopes located in the region resistant to proteolysis. Such an approach can be helpful for a much needed standardization of cTnI immunoassays and can improve the sensitivity and reproducibility of cTnI assays.
Analytical and clinical evaluation of an electrochemiluminescence immunoassay for the determination of CA 125
Authors: van Ingen Huub E , Chan Daniel W , Hubl Walter , Miyachi Hayato , Molina Rafael , Pitzel Lutz , Ruibal Alvaro , Rymer Jean C , Domke Ingrid 
Published: January 2020

Abstract
The CA 125 II assay on the Elecsys® 2010 analyzer was evaluated in an international multicenter trial. Imprecision studies yielded within-run CVs of 0.8–3.3% and between-day CVs of 2.4–10.9%; CVs for total imprecision in the manufacturer’s laboratory were 2.4–7.8%. The linear range of the assay extended to at least 4500 kilounits/L (three decades). Interference from triglycerides (10.3 mmol/L), bilirubin (850 μmol/L), hemoglobin (1.1 mmol/L), anticoagulants (plasma), and several widely used drugs was undetectable. Method comparisons with five other CA 125 II assays showed good correlation but differences in standardization. A 95th percentile cutoff value of 35 kilounits/L was calculated from values measured in 593 apparently healthy (pre- and postmenopausal) women. In 95% of patients with benign gynecological diseases CA 125 was ≤190 kilounits/L; 63% of patients with newly diagnosed ovarian carcinoma had values &gt;190 kilounits/L. A comparison of CA 125 values obtained with the Elecsys test and with other common CA 125 tests in monitored patients being treated for ovarian cancer showed identical patterns. In conclusion, the Elecsys CA 125 II assay is linear over a broad range, yields precise and accurate results, is free from interferences, and compares well with other assays.
Combinatorial search for diagnostic agents: Lyme antibody H9724 as an example
Authors: Tu Jian , Yu Zhiguang , Chu Yen-Ho 
Published: January 2020

AbstractTwo peptide libraries, Ac-MXXXXXBBRM and Ac-VXXXXXBBRM, were constructed on TentaGel solid support to search for ligands that bind tightly with the H9724 Lyme antibody. By using an on-bead ELISA, approximately 120 ligands were selected as candidates for further study. Matrix-assisted laser desorption ionization mass spectrometry analysis of the candidate ligands indicated a high rate of occurrence of certain amino acids at the randomized positions. On the basis of the initial screening results, a small library was designed and iteratively synthesized. Subsequent library screenings led to the identification of four peptides, Ac-PQEEGX-NH2 (X = R, K, A, D), that showed specific affinity to the antibody. This combination of solid-phase screening and iterative synthesis is an effective strategy for rapid identification of ligands that bind tightly with disease-specific antibodies and should be applicable, at least in principle, to other ligand-receptor systems. This combinatorial library approach can also be a useful tool for the discovery of novel diagnostic agents.
Radioimmunoassay for monitoring zidovudine in dried blood spot specimens
Authors: Mei Joanne V , Hannon W Harry , Dobbs Trudy L , Bell Carol J , Spruill Cathy , Gwinn Marta 
Published: January 2020

Abstract
We modified and evaluated a RIA for serum and used the modified RIA to measure zidovudine in dried blood spot specimens (DBSs) routinely collected for newborn screening and tested anonymously for maternally acquired HIV antibodies in the national HIV Seroprevalence Survey Among Childbearing Women. DBS calibration and quality-control materials were used to adapt the serum assay to the DBS matrix. The assay had a limit of detection of 24 μg/L serum and was used to measure zidovudine from both whole DBSs and the eluate remaining after HIV antibody screening. We initiated a pilot study to investigate the assay’s performance and assess its potential to determine the implementation of the US Public Health Service recommendations that HIV-infected pregnant women and newborns receive zidovudine treatment to reduce the risk of perinatal HIV transmission.