bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting behavior of an enzyme-linked immunoassay model by using commercially available neural network software
Authors: Vertosick F T , Rehn T
Published: January 2020

Setting up new immunoassays can be a laborious and expensive task. A relatively new form of multivariate analysis known as neural networks can be applied to this problem with potential savings in reagents and technician time. Neural network software programs for personal computers are now available. We applied one such software package (Brainmaker) to a model ELISA system for measuring human serum albumin. Random combinations of four variable ELISA conditions (antigen concentration, primary and secondary antibody titers, and time for chromagen development) were used to train a three-layered feed-forward network. The trained network was then used to predict measured absorbances as a function of the four input variables in separate cross-validation sets. The network adequately predicted the effect of the input variables on the absorbance produced. With use of such methods, optimal conditions for the linear dependence of absorbance on antigen concentration can be evaluated on the computer rather than in the laboratory, with subsequent savings of time and money.
Antibodies to casein kinase II in sera of patients with mixed connective tissue disease: evaluation with recombinant proteins
Authors: Wiemann C , Bodenbach L , Pyerin W
Published: January 2020

In this study we determined the prevalence of autoantibodies against casein kinase II (CKII) in patients positive for anti-70K marker antibodies, which is indicative of mixed connective tissue disease. An anti-CKII ELISA was established with the use of bacterially expressed recombinant CKII proteins. Eight out of 52 anti-70K-positive sera (15%) were positive for anti-CKII antibodies, which recognized preferentially the CKII alpha subunit. All control sera (n = 52) were anti-CKII negative. Thus, the occurrence of anti-CKII antibodies may be of value for differential diagnosis.
Optimal collection and storage conditions for catecholamine measurements in human plasma and urine
Authors: Boomsma F , Alberts G , van Eijk L , Man in 't Veld A J , Schalekamp M A
Published: January 2020

Improvements in methodologies for measuring concentrations of catecholamines (CA) have led to an increasing use of these compounds as markers in the screening of patients and in long-term clinical trials. Because of the associated logistical problems, we have investigated the unresolved question of optimal conditions for sample preparation and for storage of plasma and urine samples. Results show that blood should be centrifuged within 1 h after collection; the use of a refrigerated centrifuge is not necessary. Once plasma is prepared, CA are stable for 1 day at 20 degrees C, 2 days at 4 degrees C, 1 month at -20 degrees C (or 6 months with added glutathione), and up to 1 year at -70 degrees C. CA are stable at 4 degrees C for 1 month in unpreserved urine and for 4 months in urine preserved with EDTA and sodium metabisulfite. In acidified urine, CA were nearly unchanged after 1 year at 4 and -20 degrees C.
Europium(III) trisbipyridine cryptate label for time-resolved fluorescence detection of polymerase chain reaction products fixed on a solid support
Authors: Lopez E , Chypre C , Alpha B , Mathis G
Published: January 2020

We report a method for the nonradioactive detection of specific amplified target DNA, based on a new long-lived fluorescent label, europium(III) trisbipyridine cryptate [TBP-(Eu3+)]. After a polymerase chain reaction with a set of nested primers, microtiter affinity-collected hybrids were recognized by a TBP(Eu3+)-labeled antibody. The particular structure of the label containing the energy transfer units (bipyridine moieties) enables direct fluorescence measurement on the solid phase. Moreover, its stability and long lifetime contribute to the enhancement of the signal-to-noise ratio. The usefulness of this new label is illustrated by the detection of human papillomavirus type 16 DNA in clinical smears.
Coronary artery disease risk predicted by plasma concentrations of high-density lipoprotein cholesterol, apolipoprotein AI, apolipoprotein B, and lipoprotein(a) in a general Chinese population
Authors: Wu J H , Kao J T , Wen M S , Wu D
Published: January 2020

We measured lipid and lipoprotein concentrations in blood samples from control subjects and patients with coronary artery disease (CAD) in Taiwan. We found significant differences (P < 0.01) in the concentrations of high-density lipoprotein cholesterol (HDLC), apolipoprotein AI (ApoAI), apolipoprotein B (ApoB), and lipoprotein(a) [Lp(a)]. Concentrations of HDLC < 350 mg/L, ApoAI < 900 mg/L, ApoB > 800 mg/L, and Lp(a) > 200 mg/L occurred, respectively, 2.8, 5.2, 1.7, and 2.3 times more frequently in the patients than in the control group. If one considers HDLC at < 350 mg/L, ApoAI at < 900 mg/L, ApoB at > 800 mg/L, and Lp(a) at > 200 mg/L as separate risk factors for CAD, the ratio of individual patients to control subjects having 4, 3, 2, 1, or 0 risk factors was [symbol: see text] 9.4, 2.1, 0.2, 0.2, respectively. Individuals displaying three or more risk factors were found 15 times more frequently in the CAD group than in the control group. These risk factors may be used clinically for the prediction and prevention of CAD in the general population.
Hepatic and lipoprotein lipases selectively assayed in postheparin plasma
Authors: Henderson A D , Richmond W , Elkeles R S
Published: January 2020

Sensitive, reliable procedures are reported for the selective assay of lipoprotein lipase (LPL) and hepatic lipase (HL) in postheparin plasma samples. LPL is inhibited in the HL assay by inclusion of 0.76 mol/L sodium chloride in the substrate. In the LPL assay, specificity is attained by pretreating the sample with sodium dodecyl sulfate, which selectively denatures HL. This LPL method was validated by direct comparison with a procedure in which HL is inactivated by an antiserum to human HL. We used the described assays to quantify LPL and HL activity in 32 normal adults, demonstrating a clear sex difference for both enzymes. On average, the men displayed higher HL and lower LPL activities than did the women.
Transcriptional activation of the estrogen receptor
Authors: Wei L L
Published: January 2020

Almost all breast cancer tumors progress to a hormone-resistant state. Evidence is presented that the existence of mutant estrogen receptors may explain some hormone-resistant phenotypes. Breast tumor cells bearing a mutant receptor that is constitutively active and does not bind hormone would have unregulated cell growth and thus appear to be hormone-independent. Alternatively, breast cancer cells may contain estrogen receptors that are transcriptionally inactive but when co-expressed with wild-type receptors render normal estrogen receptors inactive. These cells would be considered estrogen receptor-positive but would be hormone-resistant. The hormone-resistant phenotype could be further complicated by the finding that other nonreceptor proteins may also modulate the transcriptional activity of estrogen receptors. These findings, if substantiated in vivo, could add to the complexity of the hormone-resistant phenotype. Different strategies of treatment will need to be developed to effectively treat the various subtypes of hormone-resistant breast tumors.
c-myc oncogene expression in estrogen-dependent and -independent breast cancer
Authors: Shiu R P , Watson P H , Dubik D
Published: January 2020

We demonstrate that c-myc gene expression is essential for growth of breast cancer cells. It also plays an important role in the progression of human breast cancer. c-myc gene amplification may be important for cancer cell invasion, but perhaps not essential for nodal metastasis. We also provide compelling evidence that the c-myc oncogene is an estrogen target gene in hormone-responsive breast cancer. Hormonal progression of breast cancer could be brought about by the enhanced expression of the c-myc gene, with gene amplification and enhanced c-myc mRNA stability being two major mechanisms involved.
Automated assay of methylmalonic acid in serum and urine by derivatization with 1-pyrenyldiazomethane, liquid chromatography, and fluorescence detection
Authors: Schneede J , Ueland P M
Published: January 2020

Determination of methylmalonic acid (MMA) in serum has been established as an accurate test for the diagnosis of cobalamin deficiency. We describe here the development and performance of a liquid-chromatographic assay of MMA in blood and urine. The assay is based on our recent finding that one of the carboxylic acid moieties of some short-chain dicarboxylic acids reacts with the fluorogenic reagent 1-pyrenyldiazomethane in an aqueous medium, whereas the other remains underivatized (Anal Chem 1992; 63:315-9). The pH-dependent ionization of the free carboxylic acid group of 1-pyrenylmethyl monoesters permits retention on anion-exchange columns, which are used for solid-phase extraction. The analysis is done with a cyanopropyl column coupled in series with an octadecyldimethylsilyl column. Solid-phase extraction and sample injection are carried out automatically by a Gilson ASPEC sample processor. The assay response varies linearly with MMA concentration in the range 0.1-1000 mumol/L in serum. The within-day and between-day CVs are 2.8-10.9%, and the detection limit of 5 fmol injected (approximately 20 nmol/L in serum) is sufficiently low to determine MMA in serum (mean 0.187 mumol/L, SD 0.084, range 0.044-0.431, n = 44) and urine from healthy subjects.
A theoretical evaluation of linearity
Authors: Kroll M H , Emancipator K
Published: January 2020

The measure of linearity is an important part of the evaluation of a method. According to the NCCLS guidelines (Document EP6-P), results of a linearity experiment are fit to a straight line and judged linear either by visual evaluation, which is subjective, or by the lack-of-fit test. This approach depends on the precision of the method, is not necessarily conclusive, and fails to be quantitative. We define linearity as a measure of how well a first-order (linear) polynomial fits the data compared with a higher-order (nonlinear) polynomial. The major property of a linear polynomial is that the first derivative is a constant. The nonlinearity of a method can be measured by the difference between these two polynomials (first-order and higher-order) at specific values or, as an average, the root-mean difference. This approach is independent of the precision of the assay and is conclusive, quantitative, and objective.
New insight into the comparative power of quality-control rules that use control observations within a single analytical run
Authors: Parvin C A
Published: January 2020

The error detection characteristics of quality-control (QC) rules that use control observations within a single analytical run are investigated. Unlike the evaluation of QC rules that span multiple analytical runs, most of the fundamental results regarding the performance of QC rules applied within a single analytical run can be obtained from statistical theory, without the need for simulation studies. The case of two control observations per run is investigated for ease of graphical display, but the conclusions can be extended to more than two control observations per run. Results are summarized in a graphical format that offers many interesting insights into the relations among the various QC rules. The graphs provide heuristic support to the theoretical conclusions that no QC rule is best under all error conditions, but the multirule that combines the mean rule and a within-run standard deviation rule offers an attractive compromise.
Simultaneous quantification of mannitol, 3-O-methyl glucose, and lactulose in urine by HPLC with pulsed electrochemical detection, for use in studies of intestinal permeability
Authors: Kynaston J A , Fleming S C , Laker M F , Pearson A D
Published: January 2020

The percentage of an oral dose of mannitol, 3-O-methyl glucose, and lactulose excreted in urine is used in noninvasive investigation of active and passive intestinal mucosal transport. We developed a high-pressure liquid-chromatographic method involving anion exchange and pulsed electrochemical detection that allows the simultaneous determination of all three sugar probes in urine. Sample preparation is simple: diluting, mixing with internal standard (melibiose), and desalting. With use of a Dionex 250 x 40 mm Carbopac PA-1 column and elution with an isocratic mixture of 120 mmol/L NaOH and 0.5 mmol/L zinc acetate, all sugars were resolved within 10 min. The standard curve of the method is linear to the following concentrations: mannitol 125 mg/L, 3-O-methyl glucose 300 mg/L, and lactulose 40 mg/L. The minimal detectable concentration of lactulose is 0.4 mg/L. Analytical recovery of the sugars is between 89.0% and 99.5%. The precision of estimation (CV) ranges from 1.76% to 5.6% overall. Reference intervals were established from results for 28 healthy children. The method is adaptable for the study of carbohydrates at low concentrations in other biological fluids.
Relation of lipoprotein(a) in 11- to 19-year-old adolescents to parental cardiovascular heart disease
Authors: Vella J C , Jover E
Published: January 2020

We studied several risk factors in relation to parental cardiovascular heart disease: total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein (apo) A-I, apo B, and lipoprotein(a) [Lp(a)] were determined in 322 serum samples (43 from subjects with and 279 without parental cardiovascular heart disease). The distribution of Lp(a) concentrations in our young population was similar to that of other white populations, i.e., markedly skewed, with higher frequencies at low values. As compared with children whose parents did not report cardiovascular heart disease, those with affected parents had a higher mean Lp(a) (0.23 vs 0.18 g/L; P < 0.05). Moreover, 42% of the children with parental cardiovascular heart disease, but only 19% of those with no parental cardiovascular heart disease, exhibited Lp(a) values > 0.30 g/L. These results suggest not only that Lp(a) is an important risk factor for cardiovascular heart disease, but also that Lp(a) is more strongly related to the risk of cardiovascular heart disease than are HDL- and LDL-cholesterol and apo A-I and B.
Cocaine and benzoylecgonine in saliva, serum, and urine
Authors: Schramm W , Craig P A , Smith R H , Berger G E
Published: January 2020

We studied the feasibility of using saliva to detect cocaine and benzoylecgonine. Saliva was collected as an ultrafiltrate directly in the mouth with an osmotic device. We analyzed by immunoassay matched samples of urine, blood, and salivary ultrafiltrate from 69 patients who had used cocaine within 24 h of sample collection. Cocaine concentrations were 4.9 times higher in saliva than in serum; benzoylecgonine concentrations were 2.5 times higher in serum. Seven urine and two serum samples had undetectable concentrations of cocaine, but all 69 saliva samples were positive for the drug. For benzoylecgonine detection, all urine samples were positive and three serum and one saliva sample were negative. We also analyzed 43 samples of saliva by gas chromatography/mass spectrometry: all were positive for benzoylecgonine, whereas 40 were positive for cocaine. We conclude that simultaneous measurement of cocaine and benzoylecgonine in saliva is suitable in screening for recent cocaine use.
Testosterone concentration is increased in whole saliva, but not in ultrafiltrate, after toothbrushing
Authors: Schramm W , Smith R H , Craig P A , Grates H E
Published: January 2020

The concentration of testosterone in whole saliva is significantly increased (by 9%) after toothbrushing. In ultrafiltrates of saliva collected at the same time as the whole saliva, testosterone concentrations after toothbrushing were unchanged. In 88% of the 162 whole-saliva specimens, but not in the ultrafiltrates, we also measured higher hemoglobin concentrations after toothbrushing. We conclude that the increase of testosterone in whole saliva after toothbrushing can be attributed to a protein-bound fraction. For analytes that are bound to serum proteins, salivary measurements can give spurious results. This problem can be avoided by using as a diagnostic medium an ultrafiltrate of saliva collected directly in the mouth.
Modified method for determining carcinoembryonic antigen in the presence of human anti-murine antibodies
Authors: Morrissey N E , Quadri S F , Kinders R , Brigham C , Rose S , Blend M J
Published: January 2020

The increasing use of monoclonal antibodies (MAbs) for disease diagnosis and therapy has created a class of patients at risk for systematic error in clinical testing due to interference by human anti-murine antibodies (HAMA). HAMA interference is often difficult to detect and can cause either an increase or a decrease in apparent concentrations of antigen present. We undertook a clinical study to test a HAMA-resistant enzyme immunoassay (EIA) format for carcinoembryonic antigen (CEA) determination. Using the Food and Drug Administration-approved CEA-EIA Monoclonal One-Step Assay (Abbott) with the addition of an acid/heat extraction of patients' specimens, we found that the resulting CEA values accurately reflected the patients' status. We demonstrated that the acid/heat-extracted specimens yield linear dilution curves and show analytical recoveries of added CEA in the range of 76-123% in HAMA-positive specimens and 86-103% in HAMA-negative specimens. The correlation of CEA values in extracted vs unextracted specimens from 184 patients and control subjects was 0.9963. The CEA detection limit of the assay was 1.6 micrograms/L for the extracted samples.
Ion-chromatographic determination of plasma oxalate reexamined
Authors: Petrarulo M , Cerelli E , Marangella M , Maglienti F , Linari F
Published: January 2020

This new procedure for determining oxalic acid in plasma is based on sample deproteinization with hydrochloric acid and acetonitrile and subsequent ion-chromatographic assay of the neutralized supernate. Sample pretreatment produces very clean samples, which ensures long column life. Mean analytical recovery of oxalate (5.0-10.0 mumol/L) added to plasma samples averaged 98.6 +/- 6.2%; imprecision (CV) was 5.2% (at 2.2 mumol/L) and the detection limit was 0.5 mumol/L at a signal-to-noise ratio of 5:1. Ascorbate to oxalate conversion was < 0.2%, indicating that the procedure is free from ascorbate interference. Plasma oxalate concentrations, measured in samples from 31 healthy persons, ranged from 0.8 to 3.4 mumol/L (mean 1.89, SD 0.75 mumol/L), which agrees with results from indirect radioisotopic dilution methods.
Receiver-operating characteristic (ROC) plots: a fundamental evaluation tool in clinical medicine
Authors: Zweig M H , Campbell G
Published: January 2020

The clinical performance of a laboratory test can be described in terms of diagnostic accuracy, or the ability to correctly classify subjects into clinically relevant subgroups. Diagnostic accuracy refers to the quality of the information provided by the classification device and should be distinguished from the usefulness, or actual practical value, of the information. Receiver-operating characteristic (ROC) plots provide a pure index of accuracy by demonstrating the limits of a test's ability to discriminate between alternative states of health over the complete spectrum of operating conditions. Furthermore, ROC plots occupy a central or unifying position in the process of assessing and using diagnostic tools. Once the plot is generated, a user can readily go on to many other activities such as performing quantitative ROC analysis and comparisons of tests, using likelihood ratio to revise the probability of disease in individual subjects, selecting decision thresholds, using logistic-regression analysis, using discriminant-function analysis, or incorporating the tool into a clinical strategy by using decision analysis.
Urinary neopterin as a predictive marker of coronary artery abnormalities in Kawasaki syndrome
Authors: Iizuka T , Minatogawa Y , Suzuki H , Itoh M , Nakamine S , Hatanaka Y , Uemura S , Koike M
Published: January 2020

We investigated whether urinary neopterin concentrations respond to the pathological conditions (especially coronary artery dilatation) of Kawasaki syndrome. All of 29 children with Kawasaki syndrome had very high urinary neopterin concentrations. Increased urinary neopterin concentrations coincided with fever and with monocytosis in peripheral blood. The urinary neopterin excretion peaking within the first 8 days after onset correlated with the development of coronary artery dilatation. Increased urinary neopterin concentrations indicate that cell-mediated immunity is activated in patients with Kawasaki syndrome. Endogenous interferon-gamma and activation of monocytes/macrophages may play a role in the pathogenesis of Kawasaki syndrome. Not only do neopterin concentrations correlate with symptoms in the acute phase of Kawasaki syndrome, they also act as a predictive marker of coronary artery abnormalities in affected patients.
"Direct" and total bilirubin tests: contemporary problems
Authors: Lott J A , Doumas B T
Published: January 2020

In eight unique challenges mailed by The College of American Pathologists Comprehensive Chemistry Survey to participating laboratories within 3 years, results for direct-reacting bilirubin (DBIL) were highly variable among the 12 largest peer groups, and most of the results differed greatly from the values obtained by a referred method. Peer-group mean values for total bilirubin (TBIL) were in much better agreement with each other and with those obtained by the Reference Method for TBIL. From a review of the information on the assay of DBIL provided to us by the manufacturers, we conclude that among the major causes of the large variability and bias in DBIL assays are problems with calibration, lack of a serum blank measurement, inadequate concentrations of HCl in the reaction mixture, inappropriate use of bichromatic correction methods, and possibly the use of wetting agents or surfactants in the reagent. Within-group SDs were small and generally acceptable. The among-peer-group variability in DBIL values is attributable to bias, not imprecision. We recommend several simple changes that could improve the accuracy of DBIL determinations in clinical laboratories.
Enzyme immunoassay--a new technique for estimating hemoglobin A1c
Authors: John W G , Gray M R , Bates D L , Beacham J L
Published: January 2020

We describe a method for estimating hemoglobin A1c (HbA1c) with a commercially available enzyme immunoassay system. The method is based on microtiter plate technology, utilizing an antibody raised to hemoglobin, the epitope being the Amadori product of glucose plus the first eight amino acids on the N-terminal end of the beta chain of hemoglobin. The enzyme immunoassay displays good within-batch (CV 2.3-2.4%) and between-batch (CV 2.6-5.0%) precision, and the results were not affected by different types of anticoagulant. The method was linear within the expected range of results and showed good correlation (r = 0.88-0.98) with established methods for estimating glycohemoglobin. Using this method, we obtained a reference interval of 2.8-4.9% (central 95%) for HbA1c in a nondiabetic population. The percentages of hemoglobin that were HbA1c in diabetics (6.86% +/- 2.51%) were significantly greater (P < 0.001) than in nondiabetics (3.46% +/- 0.52%).
Differences in elastase-binding activity of alpha 1-protease inhibitor and alpha 2-macroglobulin for asthma patients and control subjects with various alpha 1-protease inhibitor phenotypes
Authors: Gaillard M C , Reichberg S B , Nogueira C M , Kilroe-Smith T A
Published: January 2020

Forty-two adult patients with asthma and 30 control subjects were investigated for elastase-binding capacities of alpha 1-protease inhibitor and alpha 2-macroglobulin in plasma. The binding activities of alpha 1-protease inhibitor and alpha 2-macroglobulin in asthmatic patients with the M phenotype for the alpha 1-protease inhibitor differed in their relationship to the values in control subjects with the same phenotype [less alpha 1-protease inhibitor for asthmatics (35.1 +/- 1.8) than for controls (42.9 +/- 2.0 kU/L) (P < 0.001); more alpha 2-macroglobulin for asthmatics (6.9 +/- 0.3) than for control subjects (5.9 +/- 0.4 kU/L) (P < 0.03)]. In contrast, the patients with a deficiency allele (S, V, or Z) for alpha 1-protease inhibitor had lower activities of both alpha 1-protease inhibitor [22.1 +/- 0.1 vs 42.9 +/- 2.0 kU/L (P < 0.001)] and alpha 2-macroglobulin [4.6 +/- 0.6 vs 5.9 +/- 0.4 kU/L (P < 0.001)] than did the control subjects with the M phenotypes. The relevance of the results to the pathogenesis of asthma is discussed.
Increased phospholipase A activities in sera of intensive-care patients show sn-2 specificity but no acyl-chain selectivity
Authors: Püttmann M , Aufenanger J , von Ochsenstein E , Dürholt S , van Ackern K , Harenberg J , Hoffmann G E
Published: January 2020

Phospholipase A (PLA) activities were measured by high-performance liquid chromatography in two enzyme preparations purified from human duodenal juice and a serum pool as well as in 52 sera from 31 intensive-care patients with various diseases. On the basis of a position-specific fatty acid analysis of the natural substrate ("soybean lecithin") from a commercial PLA kit, serum activities of PLA1 could be clearly distinguished from those of PLA2, which is not possible in the usual measurements made with single-label radioactive substrates. Independent of the type of disease, all sera with highly increased PLA activities (40-200 U/L) showed nearly pure PLA2 characteristics without any preference among oleic, linoleic, and linolenic acid in the sn-2 position of the glycerophospholipid substrate. Nevertheless, very low PLA1 activities (< or = 5 U/L, most likely due to heparin perfusion therapy) could also be detected by palmitic and stearic acid release from the sn-1 position, leading to small changes in fatty acid release patterns of sera with low PLA activities. Measurements with sera from heparin-treated volunteers demonstrated that heparin therapy may initially contribute as much as 22 U/L to increased PLA1 activities but is not important under prolonged therapy. The absence of selectivity with respect to acyl-chain desaturation supports the concept of serum PLA2 as an acute-phase protein rather than a regulator of the arachidonic acid cascade.
Analysis for bismuth in tissue by electrothermal atomic absorption spectrometry
Authors: Slikkerveer A , Helmich R B , de Wolff F A
Published: January 2020

We developed a simple method for the analysis of bismuth (Bi) in biological tissue, using wet digestion for sample pretreatment. Bi was determined by electrothermal atomic absorption spectrometry with platinum as a matrix modifier to decrease the volatility of Bi. The furnace program included a gas stop for sensitivity enhancement. Analytical performance was established for Bi in kidney, liver, brain, and bone. As little as 25 ng/g wet weight can be detected in the most concentrated digests. Homogenization of bone was necessary before digestion, and its matrix showed the strongest interference. In rats exposed orally to colloidal bismuth subcitrate for 14 days, the metal could be detected in liver, kidney, and spleen but not in brain and bone. In the tissues of 12 patients who died from non-Bi-related causes, no Bi were present in kidney in the other 2.
Intra- and interlaboratory sources of imprecision in drug measurements by different techniques
Authors: Tsanaclis L M , Wilson J F
Published: January 2020

We compared the intra- and interlaboratory precision of seven techniques used to measure eight antiepileptic drugs, digoxin, and theophylline by using data from the international Healthcontrol external quality-assessment scheme. Scheme participants were supplied blind with 6 or 12 sets of duplicate lyophilized serum samples. Each set contained different drug concentrations, and duplicates were analyzed separately, 1 to 6 months apart. The intra- and interlaboratory components of assay variance were isolated and compared by Bartlett's test for homogeneity of variance. Fluorescence polarization immunoassay (Abbott) showed the best overall intra- and interlaboratory performance for a range of analytes. The largest intralaboratory errors were produced by techniques using the Syva EMIT assays. Our analysis of the data shows that for most analyte/technique combinations, intralaboratory sources of variation were more important than interlaboratory sources. Gains in assay precision will therefore result from attention to internal laboratory procedures.
Reduced bovine hemoglobin solution evaluated for use as a blood gas quality-control material
Authors: Mahoney J J , Wong R J , Van Kessel A L
Published: January 2020

We evaluated a new commercially available partially purified reduced bovine hemoglobin solution (RBHS) and a new tonometer for use in the quality control of blood gas analyzers. RBHS is manufactured in three different formulations, each corresponding to three different bicarbonate-buffering capacities and concentrations of total hemoglobin (ctHb). The P50 for each formulation of RBHS was determined to be as follows: 30.6 mmHg (4.08 kPa) for Level 1, 29.1 mmHg (3.88 kPa) for Level 2, and 28.2 mmHg (3.76 kPa) for Level 3. When RBHS and human blood samples were tonometered at three clinically significant values of PO2 and PCO2, the recovered values for PO2 and PCO2 in RBHS were comparable with those of the tonometered whole blood. Each level of RBHS also produced precise pH (SD < or = 0.006 pH units) and ctHb (SD = 1.0 g/L) values. In addition, when the temperature of a sample chamber was intentionally altered, the changes in RBHS blood gas values closely approximated the changes seen with human blood. RBHS shows more thermal sensitivity than either perfluorocarbon emulsions or aqueous buffers, which are currently being used as quality-control and proficiency testing materials.
Monitoring cancer antigen 125 in serum of ovarian cancer patients after administration of 131I-labeled F(ab')2 fragments of OC125 antibody
Authors: Reinsberg J , Schultes B , Wagner U , Krebs D
Published: January 2020

We evaluated the effect of repeated administration of OC125 F(ab')2 fragments on cancer antigen (CA) 125 determination in 210 serum samples from 30 patients. We found falsely high CA 125 concentrations in 142 (68%) samples, using a homologous CA 125 enzyme immunoassay (EIA) with OC125 antibodies. The Truquant OV2 method, which involves two other murine antibodies, and the IMx CA 125 method, which uses sheep antibodies as capture antibodies, resulted in only slightly increased (false-positive) values in some samples with exceptionally high CA 125 EIA values. We measured falsely low CA 125 values in 37 (18%) samples with the Truquant OV2 method. Interferences could be eliminated by removal of serum IgG. Our results suggest that interferences are to some extent caused by anti-idiotypic IgG induced by OC125 administration. Assays involving nonmurine anti-CA 125 antibodies as capture antibodies seem to be most suited for CA 125 determination after OC125 treatment, but in every case an apparent increase of CA 125 after OC125 infusion should be validated.
Candidate reference methods for determining target values for cholesterol, creatinine, uric acid, and glucose in external quality assessment and internal accuracy control. II. Method transfer
Authors: Thienpont L M , Leenheer A P , Stöckl D , Reinauer H
Published: January 2020

We describe the testing of transferability of candidate Reference Methods developed by INSTAND for cholesterol, creatinine, uric acid, and glucose. The methods are based on isotope dilution-gas chromatography--mass spectrometry. The study consisted of two parts: setup of the methods and self-evaluation for readiness in the collaborating laboratory, followed by independent measurements in parallel with INSTAND. Criteria used for judging the transferability and general reliability of the candidate Reference Methods were: the accuracy and precision of the collaborating laboratory and the agreement between the two laboratories. The accuracy was judged from the results on the Standard Reference Material 909 from the National Institute of Standards and Technology. For all analytes except glucose the bias from the certified value was < 0.7%. The mean intralaboratory imprecision ranged from 0.66% to 1.24%. The agreement between the results was tested by an advanced linear-regression analysis and Student's t-test. In general, the results demonstrate that the candidate Reference Methods developed by INSTAND can be successfully transferred without loss of their inherent precision and accuracy.
Dipyrone interference on several common biochemical tests
Authors: Gascón N , Otal C , Martínez-Brú C , Mercé J , Cortés M , Arcelus R , Queraltó J M , Sánchez J M , González-Sastre F
Published: January 2020

We studied the effect in vitro and in vivo of dipyrone on the determination of several biochemical tests in two analyzers, a Hitachi 747 and a Kodak Ektachem 700. From studies in vitro, we found significant interference by dipyrone (P < 0.05) in the determination of creatine kinase (CK), lactate dehydrogenase (LD), uric acid, triglycerides, cholesterol, aspartate aminotransferase, alanine aminotransferase, and urea nitrogen with both instruments, and in the determination of creatinine in the Ektachem analyzer. We also studied the effect of intravenously administered dipyrone in 14 patients. Dipyrone interfered significantly (P < 0.05) in the determination of CK, LD, uric acid, triglycerides, and cholesterol with both instruments, and creatinine only with the Ektachem analyzer. Using high-performance liquid chromatography (HPLC), we measured concentrations of dipyrone in the serum of patients who had received the drug and observed a negative correlation between the concentrations of dipyrone in the blood and the percentage of each analyte concentration.
Determination of trace elements in blood serum of patients with Behçet disease by total reflection x-ray fluorescence analysis
Authors: Dogan P , Dogan M , Klockenkämper R
Published: January 2020

The distribution of trace elements Fe, Cu, Zn, Se, and Rb was determined in sera from patients with the complete type of Behçet disease in the active stage and from healthy controls. Total reflection x-ray fluorescence was used for quantitative analysis; in general, atomic absorption spectrometry was used only for control of the Se values. Zn, Se, and Rb concentrations were significantly (P < 0.0001) lower for patients than for control subjects. No significant difference was determined in the Fe content. However, there was a significant increase in Cu in the patients so that the ratios Cu/Zn, Cu/Se, and Cu/Rb were significantly higher for the patients than for the control subjects (P < 0.0001).
Sandwich enzyme immunoassay of osteocalcin in serum with use of an antibody against human osteocalcin
Authors: Monaghan D A , Power M J , Fottrell P F
Published: January 2020

We have developed and thoroughly validated a solid-phase sandwich enzyme-linked immunosorbent assay (ELISA) on microtiter plates for osteocalcin in human serum with use of an antibody raised against human osteocalcin. We used a monoclonal antibody against bovine osteocalcin as the capture antibody; the second antibody was a polyclonal antibody against human osteocalcin. The amount of bound second antibody was determined with use of swine anti-rabbit antibody labeled with horseradish peroxidase. We demonstrated independence of volume and determined the recovery of added standard and within- and between-assay precision. The minimal detection limit for osteocalcin was between 1.0 and 1.5 micrograms/L and the midpoint of the standard curve ranged from 14 to 17 micrograms/L. The intraassay CV was < or = 8% in the range 2.7-52 micrograms/L; the interassay CV was usually < or = 15% in the same range. Analytical recovery of human osteocalcin standard added to serum samples was consistently > 90%. Values for osteocalcin measured in serum from 44 normal subjects were similar to those obtained with a competitive enzyme immunoassay (EIA) that used a monoclonal antibody against bovine osteocalcin. There was a good correlation between the two assays [r2 = 0.877, slope and intercept (+/- SE) = 0.88(+/- 0.051) and 0.316(+/- 0.523), respectively]. The range and mean (+/- SD) for the sandwich ELISA and the competitive EIA were 1.7-18.1 micrograms/L [8.7(+/- 4.4) micrograms/L] and 1.9-22.8 micrograms/L [9.1(+/- 4.4) micrograms/L], respectively.
Development and evaluation of an osteocalcin chemiluminoimmunoassay
Authors: Kao P C , Riggs B L , Schryver P G
Published: January 2020

We developed a competitive chemiluminoimmunoassay of osteocalcin that is similar to radioimmunoassay but uses acridinium-ester-labeled antigen instead of 125I-labeled osteocalcin; a second antibody immobilized on plastic beads is used to separate free and bound fractions. There was good correlation of the new chemiluminoimmunoassay (y) with a polyclonal antiserum (R102) radioimmunoassay (x) used in many previous clinical studies (r = 0.96, y = 0.968x + 2.69, Sy/x = 0.029, n = 86). The new assay recognized both the intact and the small fragment of osteocalcin in plasma and detected decreases of them (total, approximately 47%) after a 24-h infusion of parathyroid hormone. Patients with primary hyperparathyroidism had increased concentrations of intact osteocalcin. Children had higher concentrations of osteocalcin than adults did. Healthy women had greater osteocalcin concentrations at ages 50-70 years than earlier. Inverse correlations of bone mineral density and osteocalcin were found in healthy women and in women with osteoporosis.
Wheat germ lectin affinity electrophoresis of serum alkaline phosphatase with commercially available agarose gels
Authors: Mattiazzo M , Ramasamy I
Published: January 2020

We have modified a commercially available procedure involving precast agarose gels (Paragon Isopal System) to measure alkaline phosphatase (EC 3.1.3.1) isoenzymes. Including wheat germ lectin in the equilibration buffer improved the resolution of the bone and liver isoenzymes. Unlike previously described wheat germ lectin affinity electrophoresis methods, the procedure measures bone, liver, and biliary isoenzymes in a single step. There was good correlation between the affinity electrophoresis and the neuraminidase preincubation methods for the measurement of bone (r = 0.958) and liver (r = 0.962) alkaline phosphatase isoenzymes. However, the affinity electrophoresis method also quantified minor isoenzyme fractions that were poorly resolved by the neuraminidase method. The method is technically simple, reproducible, and capable of rapid handling of large workloads.
Measuring alveolar lavage fluid surfactant by fluorescence polarization
Authors: McCarroll N A , Van Lente F
Published: January 2020

We describe a procedure by which surfactant/albumin ratios in bronchoalveolar fluid (BALF) may be quantified with the Abbott Laboratories TDx fluorescence polarization analyzer and fetal lung maturity reagents. Adding albumin to BALF samples shifted the surfactant/albumin ratios to within the analytical range of the method. The analytical CV for assay of modified BALF samples was 2.9%. Ratios obtained for modified samples from normal individuals (n = 10), transplanted lungs (n = 23), and contralateral native lungs of the transplant recipients (n = 23) were significantly different (P = 0.006). The ratio obtained for these modified samples can be converted, if needed, to the ratio in the original sample by using a simple mathematical relationship and the albumin concentration of the sample. We propose that this ratio will be useful in evaluating the surfactant status of BALF, particularly in lung allografts.
Physician judgment in clinical settings: methodological influences and cognitive performance
Authors: Dawson N V
Published: January 2020

Understanding the quality of physicians' intuitive judgments is essential in determining the appropriate use of their judgments in medical decision-making (vis-a-vis analytical or actuarial approaches). As part of this process, the quality of physicians' predictions must be assessed because prediction is fundamental to common clinical tasks: determining diagnosis, prognosis, and therapy; establishing monitoring intervals; performing screening and preventive maneuvers. Critical evaluation of predictive capabilities requires an assessment of the components of the prediction process: the data available for prediction, the method used for prediction, and the accuracy of prediction. Although variation in and uncertainty about the underlying data elements are often acknowledged as a source of inaccurate predictions, prediction also can be confounded by both methodological and cognitive limitations. During the past two decades, numerous factors have been recognized that may bias test characteristics (sensitivity and specificity). These same factors may also produce bias in intuitive judgments. The use of cognitive processes to simplify judgment tasks (e.g., the availability and representativeness heuristics) and the presence of certain biases in the judgment process (e.g., ego, regret) may present obstacles to accurate estimation of probabilities by physicians. Limitations on the intuitive use of information (cognitive biases) have been demonstrated in both medical and nonmedical decision-making settings. Recent studies have led to a deepening understanding of the advantages and disadvantages of intuitive and analytical approaches to decision making. Here, many aspects of the basis for this understanding are reviewed.
Analytical goals developed from the inherent error of medical tests
Authors: Ross J W , Fraser M D
Published: January 2020

Biological variation is inherent in all medical tests and is a major source of error in clinical test interpretation. We use inherent test error due to biological variability as the touchstone by which to validate the clinical acceptability of analytical goals. Analytical goals should consist of sets of complementary limits for total error, bias, and imprecision and a medical usefulness criterion (MUC) to ensure that the total error goal is met with stated certainty. We propose analytical goals that are limits for the total error of a measurement system, the joint capability of the process control procedures and the measurement process. Thus, the goals are the allowable analytical error for proficiency evaluation, internal process control, and the total error budget for design of method performance characteristics. We define MUC as the allowable maximum proportion of test diagnostic efficiency lost due to analytical error near medical decision points. MUCs < 0.03 are not routinely clinically useful; MUCs > 0.08 allow method performance characteristics that are undesirable for general clinical use. Using MUC = 0.05 and recommendations that imprecision not exceed one-half of the biological CV, we propose that fixed bias should not exceed one-fourth to one-third of the intraindividual biological CV of the analyte and that total analytical error should not exceed 1.25 to 1.40 times the biological CV. Modification of these analytical goals may arise for reasons of documented clinical practice or process stability. Our model quantifies in medical utility terms the results of such modifications.
Cholesterol--a model system to relate medical needs with analytical performance
Authors: Wiebe D A , Westgard J O
Published: January 2020

The evolution of cholesterol testing provides an example of a systematic approach that developed to relate the medical use of a laboratory test with the analytical performance requirements for that test. Laboratories today have the capability to perform cholesterol testing with the accuracy and precision necessary to meet medical needs. This statement can be made because (a) a standard diagnostic process has been established by the National Cholesterol Education Program; (b) an accuracy base is provided through a reference method that is readily available to manufacturers and laboratories; (c) the precision of analytical systems has been improved by manufacturers; (d) operating specifications for all such systems can be established, with statistical quality-control rules to ensure adequate within-run method performance; and (e) analytical performance is monitored by proficiency testing by using national quality requirements defined by CLIA '88 for acceptability. This cholesterol model provides a logical and scientific approach that should be applicable with other analytes to assure that the analytical performance of the laboratory test satisfies medical needs.
Linking medical needs and performance goals: clinical and laboratory perspectives on thyroid disease
Authors: Hay I D , Klee G G
Published: January 2020

Diagnosis and management of thyroid disease benefit substantially from close interactions between clinicians and laboratorians. Clinicians desire reliable tests for diagnosis and management of both hypothyroidism and thyrotoxicosis. Traditionally, multitiered testing has been used, beginning with an index of free thyroxine concentration, which, if abnormal, has been followed by basal thyrotropin (TSH) measurements (for hypothyroidism) or thyrotropin-releasing hormone-stimulated TSH measurements (for thyrotoxicosis). Improvements in analytical methods for TSH have made it practical to use basal TSH measurements in serum as the first-line test for thyroid disease. However, performance guidelines are needed, because not all TSH assays work well in this role. The performance guidelines developed by the American Thyroid Association are reviewed to illustrate how they help to assure consistent analytical testing. Further improvements in TSH assays (third- and fourth-generation assays), which support measurements down to 0.01 mlU/L and 0.001 mIU/L, may provide additional advantages for classifying thyrotoxic patients and monitoring thyroxine-suppressive therapy in patients with thyroid cancer. The potential advantages of these newer assays are illustrated with case examples. Additional analytical performance monitors are proposed to help ensure that these next-generation TSH assays meet the expanded clinical needs.
Analytical performance goals for measuring prostate-specific antigen
Authors: Fritsche H A , Babaian R J
Published: January 2020

We have assessed the feasibility of using fixed-limit criteria based on medical relevance and biological variation for evaluating the analytical performance of the prostate-specific antigen (PSA) test. The estimated within-subject variation of serum PSA is on the order of 10-20% at clinical decision points. The calculated performance goals of 5-10% CV are attainable with current immunoassay technology and agree with precision goals based on clinical experience and the current clinical use of the test. However, new clinical applications of PSA may require a degree of analytical performance that current methods may not be able to provide. The PSA model demonstrates the need for biologically based fixed-limit criteria for all tumor-marker tests.