bluuebunny/crossref_metadata_2025_split huggingface dataset:
One-Step, Labeled-Antibody Assay for Measuring Free Thyroxin. II. Performance in a Multicenter Trial
Authors: Sheehan C P , Christofides N D 
Published: January 2020

Abstract
The technical and diagnostic performance of a labeled antibody radioassay for free thyroxin (Amerlex-MAB* FT4) was examined in a multicenter trial. The overall mean within-assay precision (CV) in eight centers was 6.2% at 30 pmol/L and 3.6% at 13 pmol/L concentrations of FT4. Between-assay precision was 5.4% at 18 pmol/L and 6.8% at 50 pmol/L. The euthyroid central 95% reference range for FT4 was 11.3 to 24.3 pmol/L. Results of the method correlated well with those of an analog radioimmunoassay: [Amerlex-MAB* FT4] = 1.09 [Amerlex-M FT4] + 1.50 pmol/L (r = 0.96, n = 732). Clinical performance of the assay was better than that of first-generation analog tracer assays for sera from patients with nonthyroidal illness or binding-protein abnormalities.
New Enzymatic Method with Tryptophanase for Determining Potassium in Serum
Authors: Kimura Shigeki , Asari Seishi , Hayashi Sadao , Yamaguchi Yoshihisa , Fushimi Ryo , Amino Nobuyuki , Miyai Klyoshi 
Published: January 2020

Abstract
We established a simple and rapid enzymatic method for measuring potassium ion in serum by using tryptophanase (EC 4.1.99.1) purified from Escherichia coli K12 strain (E. coli K12 IFO 3301). The presence of pyridoxal 5-phosphate promotes this enzymatic reaction, and potassium and (or) ammonium ions further accelerate it, with ammonium and potassium ions providing equivalent acceleration. We eliminated endogenous ammonium ion by using glutamate dehydrogenase (GLDH; EC 1.4.1.4), then produced ammonium ion in the presence of tryptophanase, tryptophan, and pyridoxal 5-phosphate. The concentration of formed ammonium ion, which was proportional to that of potassium ion in sample, was determined by adding GLDH to produce NADP+ in the presence of 2-oxoglutarate and NADPH; we then read the change of absorbance at 340 nm. The standard curve was linear for potassium ion concentrations up to 7.00 mmol/L. The within-assay variation (CV) was 0.89% at 5.51 mmol/L and 1.32% at 3.37 mmol/L. The day-to-day CVs were 0.99% at 6.85 mmol/L and 1.71% at 3.52 mmol/L. Analytical recoveries ranged from 98.7% to 108.9%. The correlation coefficient between values obtained with this enzymatic assay (y) and by flame photometry (x) was 0.995: y = 0.984x + 0.091 mmol/L (Sy.x = 0.105, n = 100). The presence of hemoglobin, bilirubin, or other cations little affects this system.
Biological Variation Data Applied to the Selection of Serum Lipid Ratios Used as Risk Markers of Coronary Heart Disease
Authors: Ortolá J , Castiñeiras M J , Fuentes-Arderiu X 
Published: January 2020

Abstract
The biological variation of several relative lipid quantities, calculated as the ratios between the concentrations of various serum lipids and apolipoproteins, has been estimated over a one-year period. The medians of the within-subject biological coefficient of variation, separated by sex when significant differences exist, were 15.4% for [apolipoprotein A-I]/[apolipoprotein B], 6.8% for [high-density lipoprotein (HDL)-cholesterol]/[cholesterol], 10.5% and 17.6% (women and men, respectively) for [HDL2-cholesterol]/[HDL-cholesterol], 13.6% for [HDL2-cholesterol]/[HDL3-cholesterol], 10.6% for [low-density lipoprotein (LDL)-cholesterol]/[apolipoprotein B], 10.6% and 8.7% (women and men, respectively) for [LDL-cholesterol]/[cholesterol], and 6.3% for [LDL-cholesterol]/[HDL-cholesterol]. From these data, we have calculated the critical difference for significant change detection, the index of individuality, and the goal for the between-day imprecision. Concerning within-subject biological variation, the best ratios for the detection of risk of coronary heart disease and the monitoring of intervention are [LDL-cholesterol]/[HDL-cholesterol] and [HDL-cholesterol]/[cholesterol]. The index of individuality obtained in this study indicates that the use of population-based reference values is inadequate for interpreting the ratios studied.
Serum Steroid Hormonal Profiles by Reversed-Phase Liquid Chromatography in Patients with 17-Hydroxylase Deficiency and in an Affected Family
Authors: Wei Jl-Qing , Wei Ji-Lu , Lucarelli Claudio , Zhou Xian-Teng , Wang De-Quan , Dai Wen-Ju , Li Shan , Li Si-Min , Liu Rong-Tang 
Published: January 2020

Abstract
We used an optimized isocratic reversed-phase high-performance liquid-chromatographic procedure to separate and measure 12 steroid hormones, and studied the steroid hormone profiles in sera from three patients with 17-hydroxylase deficiency (17-OHD). Two of the patients were sisters, one of whom (II-3), expressing normotension and primary amenorrhea, was diagnosed on the basis of chromatographic data and followed up for seven years. The untreated patients had obvious abnormalities on chromatograms of serum extracts, characterized by markedly increased corticosterone (B) and decreased or undetectable cortisol (F) and cortisone (E). The concentration of 11-deoxycorticosterone was much greater in the patient with classical symptoms than in the normotensive patient. In all three patients, concentrations of aldosterone were within the normal range, but concentrations of progesterone were much lower than in the patients with 21-hydroxylase deficiency. We evaluated the responses to corticotropin and dexamethasone. HPLC evaluation of the serum steroid profiles before and after corticotropin stimulation in the affected family showed that in the parents and one other sibling, concentrations of F before and after stimulation were within the normal ranges. The sums of the ratio of B to F before and the ratio of B to F after corticotropin stimulation (sigma B/F) in the parents and the other sibling were 0.292, 0.496, and 0.614, respectively, all much higher than the normal value (mean +/- SD: 0.164 +/- 0.038). Thus the sigma B/F value may be a hormonal marker of heterozygotes carrying this defect.
VALAB: Expert System for Validation of Biochemical Data
Authors: Valdiguié P M , Rogari E , Philippe H 
Published: January 2020

Abstract
In large laboratories that use "high-throughput" equipment, it is now possible to use artificial intelligence techniques to aid decision making and validation of data. This paper describes an artificial intelligence project, VALAB, that has been carried out in our laboratory. VALAB, an expert system that permits real-time validation of data, is designed to be equivalent to validation by the laboratory director. The decision produced by the expert system is based on several factors, including correlation between repeated laboratory results, physiological association between different variables, the hospital department from which the test was ordered, and the patient's age and sex. In 200 abnormal chemistry profiles randomly selected, VALAB's ability to detect abnormal cases (i.e., sensitivity = 0.75) was exceeded by only one of seven laboratory experts. However, all seven experts outperformed VALAB's measured specificity of 0.63. The VALAB system incorporates greater than 4000 rules. Operational since November 1988, it has validated greater than 50,000 medical patients' reports in real time.
Prevalence of Anti-Thyroid Peroxidase Antibodies in Serum in the Elderly: Comparison with Other Tests for Anti-Thyroid Antibodies
Authors: Roti Elio , Gardini Eliana , Minelli Roberta , Bianconi Lina , Braverman Lewis E 
Published: January 2020

Abstract
Autoimmune thyroid disease, especially chronic thyroiditis, is prevalent in elderly women and is probably the major cause of hypothyroidism in this population. The reported prevalence of chronic thyroiditis is variable, depending on the area of residence and the method(s) used to detect the presence of anti-thyroid antibodies. The recent finding that thyroid peroxidase (TPO) is the antigen for the thyroid anti-microsomal antibody (AbM) has resulted in the development of sensitive radioimmunoassays (RIA) to detect the presence of AbTPO. We have determined the prevalence of AbTPO (by RIA) in sera from 342 elderly subjects, 248 women and 94 men (mean age 80 years) residing in Reggio Emilia, Italy, and compared the results with other methods for detecting anti-thyroid antibodies, including anti-thyroglobulin (AbTg) and AbM measured by passive hemagglutination (PH) of tanned erythrocytes, and AbM measured by RIA. The prevalence of positive AbTPO was 2.3% in the men and 10.2% in the women, only slightly higher than the prevalence of AbM. However, in the antibody-positive sera, the mean value for AbTPO was approximately 20-fold greater than the upper limit of the normal range, whereas the mean value for AbM was only threefold greater. The prevalence of positive titers for AbM and AbTg measured by PH was far lower, 1.2% and 3.2%, respectively, and those sera weakly positive for AbM and AbTg by PH were strongly positive for AbTPO by RIA. AbTPO RIA may be more useful than AbM and AbTg hemagglutination and AbM RIA for detecting the presence of autoimmune thyroid disease.
Denaturing Gradient Gel Electrophoresis for Rapid Detection of Latent Carriers of a Subtype of Acute Intermittent Porphyria with Normal Erythrocyte Porphobilinogen Deaminase Activity
Authors: Bourgeois F , Gu Xue-Fan , Deybach J C , Te Velde M P , Rooij F de , Nordmann Y , Grandchamp B 
Published: January 2020

Abstract
Acute intermittent porphyria is an autosomal dominant disorder defined by a partial deficiency of porphobilinogen deaminase (EC 4.3.1.8). Clinical manifestations of the disease are characterized by acute attacks of neurological dysfunction often linked to environmental factors. Early diagnosis of gene carriers is important in the prevention of attacks and is usually achieved by determining the porphobilinogen deaminase activity in erythrocytes. However, in a subtype of acute intermittent porphyria, the enzymatic defect is restricted to nonerythropoietic cells. Different mutations have already been described that account for this phenotype in two unrelated families. We previously detected asymptomatic carriers by using mutation-specific probes after in vitro amplification of the target DNA sequence. In this study, we investigated the DNA of eight unrelated subjects with the same subtype of acute intermittent porphyria by using the polymerase chain reaction, with subsequent analysis of the amplified products by denaturing gradient gel electrophoresis. Five of these patients shared the same single-base change. This technique was quite simple and efficient for detecting asymptomatic carriers. Importantly, it is potentially useful for studying families with the same phenotypic subtype of the disease and possibly different mutations in the same DNA region.
Serum Creatinine as an Index of Renal Function: New Insights into Old Concepts
Authors: Perrone R D , Madias N E , Levey A S 
Published: January 2020

Abstract
The serum creatinine concentration is widely interpreted as a measure of the glomerular filtration rate (GFR) and is used as an index of renal function in clinical practice. Glomerular filtration of creatinine, however, is only one of the variables that determines its concentration in serum. Alterations in renal handling and metabolism of creatinine and methodological interferences in its measurement may have a profound impact on the serum concentration of creatinine. We review the fundamental principles of physiology, metabolism, and analytical chemistry that are necessary to correctly interpret the serum creatinine concentration. These principles are then applied to important clinical circumstances, including aging, pregnancy, diabetes mellitus, drug administration, and acute and chronic renal failure. Despite numerous limitations, serum creatinine remains a useful clinical tool, but more accurate measures of renal function are frequently necessary.
Highly Sensitive, Specific Enzyme-Linked Immunosorbent Assay of Neopterin and Biopterin in Biological Samples
Authors: Ogiwara S , Kiuchi K , Nagatsu T , Teradaira R , Nagatsu I , Fujita K , Sugimoto T 
Published: January 2020

Abstract
An enzyme immunosorbent assay of neopterin and biopterin on a polystyrene microtiter plate has been developed. A conjugate of neopterin or biopterin to bovine serum albumin was used to raise a specific antiserum against neopterin or biopterin in rabbits. An incubation mixture of the antiserum and samples prepared from human serum underwent another antigen-antibody reaction with the hapten fixed on the microtiter plate. The amount of antibody bound to the fixed hapten, which is inverse to the amount of hapten in the sample, was determined by using anti-rabbit IgG-horseradish peroxidase conjugate in a usual manner by measuring absorbance at 490 nm after reaction with o-phenylenediamine and hydrogen peroxide. The minimal detectable amounts of neopterin and biopterin were approximately 0.1 pmol. The specificity of the assay was so high that the assay system for neopterin completely distinguished it from biopterin, as judged from the cross-reaction of 0.002%, and vice versa. The amounts of neopterin and biopterin in human serum determined by the present method agreed well with those determined by high-performance liquid chromatography. We used the present method to determine the concentrations of neopterin in serum from healthy control subjects and patients with cancers and systemic lupus erythematosus; the results were consistent with literature data.
Two-Site Direct Immunoassay Specific for Active Renin
Authors: Simon D , Hartmann D J , Badouaille G , Caillot G , Guyenne T T , Corvol P , Pau B , Marchand J 
Published: January 2020

Abstract
A sensitive immunoradiometric assay, without an enzymatic step and specific for active human renin, was developed with use of two monoclonal antibodies (MAbs). In this assay system, the first MAb was coupled to magnetic beads (Magnogel); the second one, directed against the active form of the enzyme, was radiolabeled with 125I. The specificity of this assay was demonstrated in experiments measuring the active plasma renin concentration in the presence or absence of inactive renin. The assay, performed in two steps, was sensitive enough to detect 0.9 pg of renin per tube (3.5 ng/L). Intra- or interassay CVs were &lt; 10%. Concentrations of active plasma renin measured in normotensive subjects were between 7 and 40 ng/L.
Evaluation of the Abbott IMx® Automated Immunoassay of Prostate-Specific Antigen
Authors: Vessella R L , Noteboom J , Lange P H 
Published: January 2020

Abstract
We detail the performance characteristics of the new IMx PSA immunoassay developed by Abbott Laboratories, addressing PSA recovery, assay reproducibility, standard curve storage, lower limit of detection, dilution linearity, and correlation with the Hybritech Tandem-R PSA immunoassay. We analyzed 686 sera for PSA retrospectively, testing 555 of these concurrently with the IMx and the Tandem-R immunoassays. The IMx PSA standard curve was linear from 0 to 100 micrograms/L, and curve storage was maintained for 4 weeks. The lower limit of detection of the IMx PSA assay was &lt; or = 0.03 microgram/L; allowing for the assay precision yielded a biological detection limit of 0.06 microgram/L. We conservatively set the clinical threshold at 0.1 microgram/L. Regression analysis of dilution linearity involving 10 samples (0.44-200 micrograms/L) resulted in coefficients of correlation ranging from 0.9972 to 1.000. Reproducibility studies with 18 specimens within the range of 0.39-413.67 micrograms/L gave intra- and interassay CVs &lt; 6.5%. The interassay 95% confidence interval for a specimen containing 0.06 microgram of PSA per liter was 0.03-0.09 microgram/L. Correlation between IMx and Tandem-R PSA assay results was excellent: r = 0.9909 and slope = 0.95. Overall, the IMx PSA immunoassay, with the conveniencies of automation, curve storage, and nonisotopic handling, provided an improved lower limit of PSA detection, which allows for earlier indication of residual or recurrent disease after radical prostatectomy.
Improved Measurement of Low-Density-Lipoprotein Susceptibility to Copper-Induced Oxidation: Application of a Short Procedure for Isolating Low-Density Lipoprotein
Authors: Kleinveld H A , Hak-Lemmers H L , Stalenhoef A F , Demacker P N 
Published: January 2020

Abstract
Low-density-lipoprotein (LDL) oxidation may provide the crucial link between plasma LDL and atherosclerotic-lesion formation. Oxidation can be induced in vitro by incubating LDL with cells or metal ions and can be measured by continuously monitoring conjugated-diene absorbance at 234 nm. Measurement of LDL oxidizability was improved by performing the assay with 0.05 g of LDL-protein per liter of phosphate buffer containing 1 mumol of EDTA, by initiating oxidation by adding CuCl2 (5 mumol/L) at 30 degrees C, and by using a short-run ultracentrifugation method for isolating LDL, which reduced the time needed for obtaining purified LDL and thus reduced in vitro oxidation. LDL apolipoprotein analysis and oxidizability determination showed that this method is better than the longer sequential-isolation procedure. Adding butylated hydroxytoluene (BHT) to plasma as an antioxidant unpredictably increased the LDL oxidation lag time, making BHT unsuitable as an antioxidant. Adding EDTA appeared to be sufficient to prevent in vitro oxidation. Additionally, the diene production correlated highly with the concentration of thiobarbituric acid-reactive substances (r = 0.97). No relation between the vitamin E content of LDL and the oxidation lag time was found.
Laboratory Evaluation of the GlucocardTM Blood Glucose Test Meter
Authors: Lewis B D 
Published: January 2020

Abstract
The Glucocard (Kyoto Daiichi Kagaku) blood glucose meter is designed for self-monitoring of blood glucose concentrations in capillary blood through use of an electrochemical test strip. Evaluated in this laboratory, the Glucocard had CVs of 4.6%, 6.6%, and 3.5% at blood glucose concentrations of 2.4, 4.1, and 18.9 mmol/L, respectively. The meter's response varied linearly with blood glucose concentration between 2.2 and 27.8 mmol/L. Hemolysis, urate, ascorbate, and acetaminophen interfered by &gt; 5%. Different hematocrits, in the range 0.20-0.70, did not affect the measured glucose concentration. Comparison with glucose results measured in whole blood with a NOVA Stat Profile 5 instrument yielded the following: Glucocard = 0.898 NOVA--0.184 (r = 0.995). The main advantages of the Glucocard are its small sample volume (5 microL), wide linear range, and fully automated sample-handling steps, which reduce user-related variability.
AxonTM Clinical Chemistry Analyzer Evaluated According to ECCLS Protocol
Authors: Brenna S , Prencipe L 
Published: January 2020

Abstract
We assessed the analytical performance of the Axon system (Bayer Diagnostici), according to the European Committee for Clinical Laboratory Standards guidelines, for assay of 12 analytes: cholesterol, creatinine, glucose, total protein, urea, uric acid, alkaline phosphatase, alpha-amylase, aspartate aminotransferase, creatine kinase, sodium, and potassium. The field evaluation lasted approximately 5 months and involved the collection of approximately 10,000 data points with the Axon. The following results were obtained: The highest CVs for controls and human sera at different concentration/activity values were 2.2% for within-run imprecision (n = 60; 3 days, pooled estimate) and 3.5% for the between-day imprecision (n = 20 days). Close correlation was found with results for patients' specimens assayed with comparative instruments (Hitachi 717 for substrates and enzymes, Beckman Synchron EL/E4A for electrolytes). No drift was observed during 8 h of operation. The linearity range was broad, sometimes exceeding the manufacturer's claims. No sample-, reagent-, or cuvette-related carryover was found. Measurement of control sera gave results within +/- 5% of the assigned values. We conclude that good reliability and practicability make the Axon system suitable for laboratories with various needs.
Influence of Obesity on Plasma Fructosamine Concentration
Authors: Woo J , Cockram C , Lau E , Chan A , Swaminathan R 
Published: January 2020

Abstract
The influence of obesity on plasma fructosamine concentration was studied in 68 diabetic and 1335 nondiabetic subjects from a Chinese community. Obese nondiabetic men (body mass index &gt; 25 kg/m2) had lower fructosamine concentrations than nonobese nondiabetic men (body mass index &lt; or = 25 kg/m2); the pattern was similar for diabetic women. Stepwise multiple-regression analysis showed that, apart from known factors (total protein, albumin, and indices of glycemic control), fructosamine was also associated with body mass index and plasma fasting triglycerides. However, the contribution of these were small except in diabetic women. We conclude that the effect of obesity on fructosamine is small.
Using 16O35CL to Correct for Chloride Interference Improves Accuracy of Urine Arsenic Determinations by Inductively Coupled Plasma Mass Spectrometry
Authors: Kershisnik M M , Kalamegham R , Ash K O , Nixon D E , Ashwood E R 
Published: January 2020

Abstract
We have observed inaccurate urine arsenic values with the method of isobaric fractionation, which was designed to correct for the 40Ar35Cl interference with 75As quantitation by inductively coupled plasma mass spectrometry. Isobaric fractionation, which is based on ion intensities at m/z 77 and 82, consistently underestimates the 40Ar35Cl interference and overestimates urine arsenic. We present an improved method for identifying the argon-chloride interference. We observed that signal intensities for the species 16O35Cl and 40Ar35Cl are proportional (I75 = 0.0295 x I51 - 14.7, r2 = 0.998; where Ix is the normalized ion intensity at m/z X) in water and urine, over a broad range of chloride concentrations (0-800 mmol/L). The proportionality constant is remarkably stable within a run (mean and SD, 0.0295 +/- 0.0023, based on 10 replicates of five chloride calibrators, 0, 100, 200, 400, and 800 mmol/L). Increased sensitivity (50-fold) for detecting the 40Ar35Cl interference provides improved accuracy for urine arsenic quantitation as demonstrated by a split-sample comparison with graphite-furnace atomic absorption spectrophotometry.
Automated Analysis for Free and Short-Chain Acylcarnitine in Plasma with a Centrifugal Analyzer
Authors: Roe D S , Terada N , Millington D S 
Published: January 2020

Abstract
We describe a fully automated, spectrophotometric assay of free and total carnitine in plasma ultrafiltrates. The method, suitable for routine application in most hospital laboratories, incorporates the hydrolysis of acylcarnitines to free carnitine within the program of a Cobas Fara II centrifugal analyzer. The hydrolysis is monitored and calibrated with standard solutions containing octanoylcarnitine. Results correlated well with those from a reference isotope-dilution mass spectrometric assay. The ability to analyze a batch of samples for both free and total carnitine within 90 min enables analysis of &gt; or = 100 samples per day. Used in conjunction with acylcarnitine species identification by mass spectrometry, the Cobas assay facilitates the diagnosis of carnitine-deficiency syndromes and specific metabolic disorders.