bluuebunny/crossref_metadata_2025 huggingface dataset:
Cholinesterase inhibition: complexities in interpretation
Authors: Lotti M
Published: January 2020

Cholinesterases are measured to assess exposures to or effects of organophosphorus esters and carbamates. Plasma butyrylcholinesterase is usually most sensitive to inhibitors, but it has no known physiological function(s); its inhibition reflects exposure. The physiological function of erythrocyte acetylcholinesterase (AChE) also is not known, but the enzyme is the same as that involved in synaptic transmission and its measurement is used to mirror effects on the nervous system. Erythrocyte AChE has large inter- and intraindividual variation, and small changes are detectable by comparison with preexposure values. The relation between inhibition of erythrocytes and nervous tissue AChE depends on the pharmacokinetics of inhibitors. Usually, erythrocyte AChE inhibition overestimates that in the nervous system. Pharmacodynamic factors such as spontaneous reactivation and aging of inhibited enzyme should also be considered in assessing AChE inhibition. Other factors, such as timing of measurement, add complexity because erythrocyte AChE inhibition persists longer than that in the nervous tissues. Cholinergic transmission might also be impaired because of direct effects of organophosphorus esters and carbamates on receptors.
Serum oncoproteins in asbestosis patients
Authors: Partanen R , Koskinen H , Oksa P , Hemminki K , Carney W , Smith S , Brandt-Rauf P
Published: January 2020

Using ELISAs, we determined the concentrations of transforming growth factor alpha (TGF-alpha), the extracellular domain of the erbB-2 receptor (erbB-2 ECD), and mutant p53 protein in stored serum samples of asbestosis patients with and without cancer and control subjects (without asbestosis or cancer). The percentage of individuals in these three groups with increased serum concentrations of TGF-alpha, erbB-2 ECD, and mutant p53, respectively, were: asbestosis patients with cancer, 36%, 16%, 19%; asbestosis patients without cancer, 38%, 19%, 6%; control subjects, 0%, 5%, 10%. Although differences in serum positivity for these oncoproteins were apparent among these groups, the differences did not achieve statistical significance (P > 0.05). In several of the cancer cases, increased concentrations of TGF-alpha, erbB-2 ECD, and mutant p53 were also detected in the stored serum samples collected years before the clinical diagnosis of disease.
External quality assessment in clinical neurochemistry: survey of analysis for cerebrospinal fluid (CSF) proteins based on CSF/serum quotients
Authors: Reiber H
Published: January 2020

Participants (230) from Germany and 20 laboratories in 11 European countries took part in a newly designed cerebrospinal fluid (CSF) survey distributed by INSTAND. Conventional proficiency testing for albumin, IgG, IgA, and IgM in CSF and serum, for total protein in CSF, and for oligoclonal IgG in CSF and serum was combined with evaluation and interpretation of CSF/serum quotients in quotient diagrams. The correct detection of a blood-CSF barrier dysfunction and the pattern of intrathecal immunoglobulin synthesis was judged. The accuracy of CSF/serum quotients and their clinically relevant interpretation was given first priority as a new concept in quality assessment. The main result of the surveys was to confirm that CSF/serum quotients of proteins represent method-independent values approaching the quality of reference values. This finding has consequences for internal quality control of CSF analysis and for accreditation bodies. The sensitivity of the methods for quantifying IgA and IgM in CSF and for detecting oligoclonal IgG fractions is discussed.
Simultaneous determination of alcohols and ethylene glycol in serum by packed- or capillary-column gas chromatography
Authors: Livesey J F , Perkins S L , Tokessy N E , Maddock M J
Published: January 2020

We developed a packed-column chromatographic procedure capable of simultaneous quantitation of methanol, ethanol, isopropanol, acetone, and ethylene glycol. This method was then updated to a rapid, sensitive, wide-bore capillary method. The packed-column system uses direct injection of 1 microL of Na2WO4/H2SO4-deproteinized serum onto a 1.8 m x 2 mm (i.d.) column packed with 80/100 HayeSep R. A linear temperature gradient from 90 to 205 degrees C allows complete elution of all components within 20 min; minimum detection limits are 2 mmol/L. The wide-bore capillary method uses 0.1 microL of sample deproteinized by ultrafiltration, injected onto a 30 m x 0.53 mm (i.d.) 3-microns Rtx-200 (Restek) column. Baseline resolution to a minimum detection limit of 0.1 mmol/L of all compounds is achieved in 5 min with a linear temperature gradient from 40 to 250 degrees C and dual internal standards of n-propanol and 1,2-butanediol.
Discordance between results for serum troponin T and troponin I in renal disease
Authors: Bhayana V , Gougoulias T , Cohoe S , Henderson A R
Published: January 2020

Two patients were investigated for unexplained increases in troponin T. In the first patient, who had rhabdomyolysis and acute renal failure, troponin T reached a peak value of 13.50 micrograms/L (67.5-fold the upper reference limit). The second patient had chronic renal failure and the troponin T peak value was 2.85 micrograms/L (14.3-fold the upper reference limit). Clinical investigations indicated no evidence of myocardial damage. Serum or plasma specimens were analyzed for total creatine kinase (CK), CK-2 mass, CK-2 isoform ratio, myoglobin, troponin T, troponin I, and myosin light chains; all except troponin I were at above-normal concentrations. We also investigated six additional renal patients with above-normal troponin T; troponin I was slightly increased in only one of these six patients. Our findings demonstrate discordance between results for troponin T and troponin I in renal patients.
Measurement and physiological significance of lipoprotein and hepatic lipase activities in preheparin plasma
Authors: Watson T D , Tan C E , McConnell M , Clegg S K , Squires L F , Packard C J
Published: January 2020

A radiochemical method for selective measurement of postheparin lipase activities was adapted to analyze lipoprotein lipase and hepatic lipase in preheparin plasma. The assay sensitivity was increased about four-fold by doubling both the volume of plasma used and the volume of lipolytic products taken for liquid scintillation counting, and was further improved by increasing the incubation period by 50% to 90 min. Rabbit antiserum to human hepatic lipase was unsuitable for the selective measurement of lipoprotein lipase because of apparent endogenous lipolytic activity. Preheparin hepatic lipase, however, was sensitive to inactivation by sodium dodecyl sulfate (SDS), the inhibition being greatest (> 90%) for plasma incubated with an equal volume of 40 mmol/L SDS. Intra- and interassay CVs for the two enzymes were 12.5-14.6% and 17.4-19.7%, respectively. In a cross-sectional study of 84 healthy subjects, pre- and postheparin hepatic lipase activities were higher in men than women, were correlated with indices of obesity, and were significantly correlated with one another, which explained the association of the former with plasma concentrations of high-density lipoprotein (HDL), HDL2, and small, dense low-density lipoproteins. There was no significant relationship between pre- and postheparin lipoprotein lipase activities, but the former were correlated with plasma concentrations of free fatty acids (FFA) and very-low-density lipoprotein. Apparently, preheparin activities of hepatic lipase, but not of lipoprotein lipase, may be a useful measure of the physiological function of "whole body" enzyme activity in cross-sectional and metabolic studies, where heparinization is not possible. Preheparin lipoprotein lipase activities, however, may reflect displacement of the enzyme by FFA and subsequent binding to remnants of triglyceride-rich lipoproteins.
Measurement of methemoglobin in neonatal samples containing fetal hemoglobin
Authors: Speakman E D , Boyd J C , Bruns D E
Published: January 2020

Because of the potential for methemoglobinemia during nitric oxide therapy in newborns, methods are needed to accurately quantify methemoglobin (MetHb) in the presence of the high concentrations of fetal hemoglobin (Hb F), bilirubin, and lipids seen in these patients. Spectral differences between fetal and adult Hbs invalidate assumptions of conventional multiwavelength Hb photometry, so we evaluated an "overdetermined" system (Ciba-Corning Model 270), in which absorbances at seven wavelengths are measured to quantify four Hb derivatives. Adult and umbilical cord blood (Hb F 96%) samples were prepared to contain known MetHb fractions. Measured MetHb was linear in cord blood to > or = 15% MetHb. Within-run precision (CV) was < 2.2% (n = 10) at each of seven MetHb fractions between 5% and 100%. Measured (y) and expected (x) MetHb fractions in cord blood were in good agreement (y = 1.0200x + 0.100, Sylx = 0). Added bilibrubin (200 mg/L serum) and lipid (30 g/L) did not interfere. No significant differences were seen for adult and cord blood samples with identical MetHb fractions (P = 0.72), whereas a significant difference was noted with an exactly determined system (P = 0.0033). At clinically relevant MetHb fractions (< 15%), a trend towards increased values in cord blood was noted with an exactly determined system (y = 1.0520x + 0.7600). We conclude that this overdetermined system measures MetHb accurately in samples from patients with large concentrations of Hb F.
Clinical capillary electrophoresis
Authors: Landers J P
Published: January 2020

Capillary electrophoresis is a relatively new analytical technique that has begun to have an impact in the clinical laboratory, both for routine analyses and for those that are more esoteric. Its potential for automated, rapid, high-efficiency separations makes it appealing as a replacement for some of the more labor-intensive assays carried out in electrophoretic gels and as a complement to companion techniques such as HPLC. Among the many attractive characteristics of this technology is its versatility for analyses of a diverse spectrum of analytes, ranging from small organic ions to macromolecular protein complexes or DNA. The focus of this commentary is to familiarize the clinical scientist with the instrumentation and principles of capillary electrophoretic separation and to review the recent research demonstrating the applicability of this technology to the clinical laboratory.
Electrochemical dehydrogenase-based homogeneous assays in whole blood
Authors: Yao H , Halsall H B , Heineman W R , Jenkins S H
Published: January 2020

An electrochemical method has been developed for determining NADH in whole blood for dehydrogenase-based assays by flow-injection analysis. NADH generated by dehydrogenase is oxidized by an electron-transfer coupling reagent, 2,6-dichloroindophenol (DCIP). The reduced form of DCIP (DCIPH2) is measured amperometrically by flow-injection analysis. Endogenous interferents were inhibited by p-hydroxymercuribenzoate. Electrode fouling by proteins was not observed under assay conditions. The Emit theophylline enzyme immunoassay and the hexokinase glucose assay were used as models. For the glucose assay, the intraassay CVs were 15% at 0.31 g/L and 3.5% at 1.82 g/L. Recoveries of glucose from whole blood (compared with that for aqueous standards) were 109%, 97.9%, and 101% at 0.050, 2.00, and 5.00 g/L glucose, respectively, and 104%, 101%, and 102% for theophylline at concentrations of 5.0 (low), 16.4 (medium), and 30.2 (high) mg/L, respectively, with corresponding precisions of 12%, 9.5%, and 8.8%. Both assays correlated well with results by reference methods. These studies demonstrate that this method can measure NADH in whole blood without prior separation and that it is potentially applicable to other dehydrogenase-based assays in whole blood.
Simultaneous assessments of exocrine pancreatic function by cholesteryl-[14C]octanoate breath test and measurement of plasma p-aminobenzoic acid
Authors: Bruno M J , Hoek F J , Delzenne B , van Leeuwen D J , Schteingart C D , Hofmann A F , Tytgat G N
Published: January 2020

Two noninvasive tests for assessing pancreatic exocrine function, the cholesteryl-[14C]octanoate breath test and the HPLCN-benzoyl-tyrosyl-p-aminobenzoic acid/p-aminosalicylic acid (NBT-PABA/PAS) test, were simultaneously performed in nine patients with pancreatic exocrine insufficiency due to chronic pancreatitis and in nine healthy volunteers. 14CO2 output in breath and plasma PABA concentration rose slowly in patients but increased rapidly in healthy subjects. The measurement time giving the best discrimination between both groups was 120 min for the cholesteryl-[14C]octanoate breath test and 90 min for the plasma PABA test. At these points, both single-sample tests had essentially identical diagnostic sensitivity. The diagnostic sensitivities of the two single-sample tests were equal to that of the cumulative 6-h urinary PABA recovery and the cumulative 6-h urinary PABA/PAS ratio. We conclude that, for both the cholesteryl-[14C]octanoate breath test and the plasma PABA test, a single test sample is sufficient for rapid detection of impaired exocrine pancreatic function.
Los Angeles County-University of Southern California Medical Center clinical pathology case conference: extreme hypermagnesemia in a neonate
Authors: Huey C G , Chan K M , Wong E T , Nelson J M , Durand M
Published: January 2020

A preterm male infant born at 33 weeks of gestation developed respiratory depression and apnea at approximately 20 h after birth. Laboratory tests indicated severe hypermagnesemia, acidosis, and hypercalcemia. Cord blood and maternal blood concentrations of magnesium were normal. The effects and possible causes of hypermagnesemia are reviewed. The infant recovered with treatment, although the etiology of his hypermagnesemia remains unknown.
Automated dibucaine number measurement with DuPont Dimension ES and AR analyzers
Authors: Holownia P , Newman D J , Bruno C , LaGamba P , Gerrits M , Salemink G , Ossani M , Price C P
Published: January 2020

We report a fully automated method for determining dibucaine number (DN) in a single-run procedure involving Dimension cholinesterase (CHE) Flex pseudo-(P)CHE reagents. The method was developed and optimized with the "open channels" and "kinetic" software facilities of the Dimension-ES instrument, where the DN is calculated automatically by an algorithm from the ratio of the uninhibited and inhibited rates, measured bichromatically, from a single analysis. The protocol was satisfactorily assessed for substrate depletion, linearity, reagent stability. and the effects of different dibucaine concentrations. Validation was performed across a range of CHE activities (1.5-22 kU/L) representing the three main genotypes, UU, UA, and AA. The respective DNs (mean +/- SD), determined on the Dimension-ES, were 82.0 +/- 1.6 (n = 32), 71.0 +/- 3.1 (n = 10), and 23.0 +/- 2.7 (n = 14), with corresponding imprecisions (CV) of 0.3%, 0.6%, and 5.2% (intraassay) and 0.7%, 0.7%, and 8.6% (interassay). Comparisons with reference (x) laboratory values and the DuPont aca (x') procedure (n = 53) gave regression equations of: y = 0.88x + 11.2, r = 0.99, and y = 0.85x' + 11.9, r = 0.99. A separate trial conducted with a Dimension-AR instrument gave similar performances. We conclude that the new DN method is fast, efficient, and appropriate for clinical use.
Vitamin C and glycohemoglobin
Authors: Weykamp C W , Penders T J , Baadenhuijsen H , Muskiet F A , Martina W , van der Slik W
Published: January 2020

Three groups of 10 age- and sex-matched nondiabetic volunteers took 0, 750, or 1500 mg of vitamin C each day for 12 weeks. Glycohemoglobin (GHb) was measured by HPLC, electrophoresis, affinity chromatography, and immunoassay at baseline (-4 weeks and -1 day), during supplementation (6 weeks and 12 weeks), and after supplementation ended (6 and 12 weeks). Plasma vitamin C increased twofold during supplementation but, in contrast with the results of Davie et al. (Diabetes 1992; 41:167-73), there were no between-group differences in GHb, glucose, and fructosamine concentrations. Fructosamine may have increased with storage time. The net effects of vitamin C on absolute GHb at 12 weeks vs -1 day (and at 12 weeks vs 12 weeks after) in % GHb amounted to: HPLC -0.035 (-0.050); electrophoresis +0.005 (+0.035); affinity chromatography -0.070 (+0.015); and immunoassay -0.110 (+0.025). We conclude that supplementation of nondiabetics with 750 or 1500 mg of vitamin C daily for 12 weeks does not cause interference in GHb determinations by HPLC, electrophoresis, affinity chromatography, or immunoassay, and does not reduce in vivo Hb glycation.
Direct determination of lipoprotein(a) cholesterol by ultracentrifugation and agarose gel electrophoresis with enzymatic staining for cholesterol
Authors: Nauck M , Winkler K , Wittmann C , Mayer H , Luley C , März W , Wieland H
Published: January 2020

Lipoprotein(a) [(Lp(a)], a low-density lipoprotein (LDL)-like particle, contains in addition to LDL a specific protein component, apolipoprotein(a) [apo(a)]. Conventionally, Lp(a) has been measured by immunological methods that distinguish between Lp(a) and LDL by dealing with apo(a) as an antigen. We describe a new method to determine Lp(a) on the basis of its cholesterol content. Very-low-density lipoproteins were removed from serum by preparative ultracentrifugation at a density of 1.006 kg/L. The infranate was subjected to agarose gel electrophoresis to separate Lp(a) and LDL. Lp(a) cholesterol was then determined by direct enzymatic staining for cholesterol. On electrophoresis of the > 1.006 kg/L (bottom) fraction, Lp(a) migrates to the pre-beta position, regardless of the genetic apo(a) isoform. The interassay CVs of Lp(a) cholesterol determinations ranged from 6.9% to 11.5%, and the results correlated well with the Lp(a) concentrations measured by immunonephelometry (r = 0.937). There was an inverse relation between the molecular mass of the genetically determined apo(a) isoforms and Lp(a) cholesterol concentrations. Patients with angiographically proven coronary artery disease (CAD) had significantly more Lp(a) cholesterol than healthy controls did. The ratio of Lp(a) cholesterol to immunologically determined Lp(a) tended to be lower in CAD patients, suggesting that Lp(a) particles contained less cholesterol than apo(a). In addition, the new method allows determination of LDL cholesterol without contamination by Lp(a).
Financial viability of screening for drugs of abuse
Authors: Peat M A
Published: January 2020

Urine drug testing is now a common practice in the American workplace; a recent survey indicated that > 90% of companies with > 5000 employees have some type of testing program. These programs have indeed reduced the rate of drug-positive test results; for example, recent data from the Federal Aviation Agency show that the rate for 1993 was 0.82% compared with 0.95% for 1992. Many corporations have stated that urine drug testing, as a component of a substance abuse policy, results in significant savings, e.g., from decreased absenteeism and turnover. The United States Postal Service recently completed a longitudinal study on the economic benefits and found that, over the average tenure of an annual intake of employees, there were savings of more than $100 million. Although this study clearly demonstrates the financial benefits of preemployment drug testing, the decision to test is not based solely on this but also on the regulatory environment and on the potential impact of a major accident attributable to the use of drugs or alcohol in the workplace.
D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK): alternative anticoagulant to heparin salts for blood gas and electrolyte specimens
Authors: Lyon M E , Fine J S , Henderson P J , Lyon A W
Published: January 2020

D-Phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), a selective thrombin inhibitor, was evaluated as an alternative anticoagulant to lithium heparin (LiHep) for blood gas and whole-blood electrolyte analyses. Initial studies in serum revealed a negative proportional bias for ionized calcium (iCa) concentration measured in the range of increasing concentrations of LiHep (-0.02 mmol/L iCa per 33 kIU/L), whereas no bias in iCa concentration was detected with increasing concentrations of PPACK. No anticoagulant-dependent changes in serum sodium, potassium, chloride, glucose, lactate, ionized magnesium, or pH were detected with either PPACK or LiHep. Similarly, no bias was observed in the measurement of whole-blood PO2, PCO2, pH, or sodium or potassium concentrations with either anticoagulant. Whole blood anticoagulated with LiHep (33 kIU/L) demonstrated a consistent -0.06 +/- 0.01 mmol/L bias for iCa compared with a nonanticoagulated whole-blood control. In comparison, no iCa bias was observed with PPACK-anticoagulated whole blood. We conclude that PPACK has ideal bias-free properties as an anticoagulant in analyses for blood gases, electrolytes, and iCa.
Undercarboxylated osteocalcin and development of a method to determine vitamin K status
Authors: Sokoll L J , O'Brien M E , Camilo M E , Sadowski J A
Published: January 2020

We developed a RIA involving a polyclonal antibody against bovine osteocalcin, which has a carboxy-terminal epitope. Although the antibody recognizes both native and descarboxy osteocalcin, the two forms of osteocalcin were differentiated by adsorption to barium sulfate, taking advantage of the calcium-binding properties of the vitamin K-dependent gla domain. To test the clinical application of undercarboxylated osteocalcin, we examined the effect of minidose warfarin on this measure in nine healthy subjects, ages 60 to 80 years. The percentage of undercarboxylated osteocalcin increased by 170% +/- 36% (mean +/- SE) after 7 days of treatment with warfarin, 1 mg/day. The effectiveness of undercarboxylated osteocalcin as a sensitive measure of vitamin K nutritional status was further established when concentrations dropped to 17% +/- 14% below baseline with 2 days of repletion with vitamin K1, 5 mg/day, during which prothrombin times did not leave the normal range.
Effect of hemodialysis on total antioxidant capacity and serum antioxidants in patients with chronic renal failure
Authors: Jackson P , Loughrey C M , Lightbody J H , McNamee P T , Young I S
Published: January 2020

Cardiovascular disease is the major cause of mortality in patients receiving hemodialysis for chronic renal failure. Increased lipid peroxidation and depletion of chain-breaking antioxidants may contribute to increased risk of atherosclerosis. We have therefore assessed the effect of a single episode of hemodialysis on antioxidant status in 22 patients and control subjects. Overall, total antioxidant capacity of serum was increased in dialysis patients, but there was a marked reduction after hemodialysis [571 +/- 31 vs 342 +/- 22 mumol/L Trolox (water-soluble vitamin E analog) equivalents, P < 0.001]. The increase in total antioxidant capacity before hemodialysis was almost entirely due to relatively high serum urate. Among individual chain-breaking antioxidants, dialysis led to a decrease in urate (398 +/- 15 vs 136 +/- 12 mumol/L, P < 0.001), ascorbate (10.5 +/- 1.7 vs 5.9 +/- 1.0 mumol/L, P < 0.01), and lipid-corrected tocopherol (4.70 +/- 0.56 vs 4.26 +/- 0.39 mumol/mmol cholesterol, P < 0.05). Protein thiol groups increased after dialysis (328 +/- 16 vs 422 +/- 22 mumol/L, P < 0.001), whereas albumin remained unchanged (40.1 +/- 1.1 vs 41.0 +/- 1.6 g/L, not significant). Although total antioxidant capacity of serum is increased in hemodialysis patients, depletion of key chain-breaking antioxidants may lead to accelerated atherogenesis.
Assay of plasma testosterone during the first six months of life: importance of chromatographic purification of steroids
Authors: Fuqua J S , Sher E S , Migeon C J , Berkovitz G D
Published: January 2020

Determination of the plasma concentration of testosterone (T) is important in evaluating infants born with ambiguous genitalia and micropenis, and several commercially available kits provide a direct assay of T in unextracted plasma. Using plasma samples obtained from 36 subjects < 6 months old, we compared the concentration of plasma T measured by RIA after extraction and purification by column chromatography with the T concentration measured in a direct assay. When aliquots of samples were purified before RIA, the concentration of T was markedly lower than in the direct assay. In the first 3 weeks postpartum, results of the direct assay were 3.8-fold greater than those obtained after purification. This difference decreased over time, and by age 2 months there was fairly good agreement between the two methods. These data indicate that some direct assays of plasma T are inappropriate during the first 2 months postpartum.
Interpretation of serial measurements of international normalized ratio for prothrombin times in monitoring oral anticoagulant therapy
Authors: Lassen J F , Kjeldsen J , Antonsen S , Hyltoft Petersen P , Brandslund I
Published: January 2020

Despite careful monitoring of oral anticoagulant treatment (OAT), some international normalized ratio (INR) for prothrombin time values will fall outside the therapeutic range. Considerable changes in serial INR results from OAT patients may be caused by random fluctuation alone, and, for statistical reasons, a fraction of the INR values will fall outside therapeutic range and interfere with dose adjustments. On the basis of therapeutic intervals and statistical evaluation of reference changes, we suggest and discuss an alternative method for interpretation of serial INR measurements. Retrospective evaluation of serial measurements of INR from OAT patients revealed an "overshooting" phenomenon. When a dose was adjusted on the basis of insignificant change in INR value, the subsequent INR value generally fell in the opposite direction. If a further change of dose was initiated because of the new INR value, a similar course in the opposite direction was observed. This "ping-pong" effect renders patients in a fluctuating state of anticoagulation and may introduce increased risk of complications. The suggested method provides an objective criterion for dose adjustments in OAT, which should reduce patients' risk.
The changing role of the clinical laboratory scientist: coming out of the basement
Authors: Wilding P
Published: January 2020

The position of clinical chemistry within the discipline of laboratory medicine is firmly established. As a result, pathologists, chemists, and scientists have been attracted to an emerging field full of promise and expectations. For most, the expectations of a rewarding career and growth of the discipline have been met. However, in a climate where factors such as "capitation" and "managed care" influence every facet of healthcare, many are reviewing their expectations and wondering whether the 21st century will bring the same promise enjoyed by the pioneers in the 20th century. In the future, laboratory scientists must align their expectations to the demands for new technologies, medical practices, and healthcare systems that will require justification for all activities, expense, and personnel. To succeed in this new environment, the clinical chemist will need excellent managerial skills, an understanding of how to articulate the benefits of technologies and laboratory tests, and a willingness to embark on a career of unceasing education.
Metaanalysis in clinical chemistry: validation of cardiac troponin T as a marker for ischemic heart diseases
Authors: Wu A H , Lane P L
Published: January 2020

Metaanalysis is a method that incorporates the pooling of previously published results to produce more statistically significant results. We used metaanalysis to examine the role of a new cardiac marker, cardiac troponin T (cTnT), in patients with ischemic heart disease. Metaanalysis of six articles and one abstract on cTnT showed that this marker was just as sensitive as creatine kinase MB isoenzyme (CK-MB) for the retrospective diagnosis of acute myocardial infarction (AMI) 12-48 h after onset but less specific. Most of these articles showed that cTnT was increased in non-AMI patients with unstable angina pectoris. In a metaanalysis of four papers, two abstracts, a letter, and an unpublished manuscript, we examined the prognostic role of cTnT in non-AMI cardiac patients. For an unfavorable endpoint defined as cardiac death, AMI, or the need for coronary artery revascularization, the results demonstrated that abnormal concentrations of cTnT were associated with a higher risk for a poor outcome than were normal concentrations of cTnT. We also compared cTnT with CK-MB for risk stratification. Metaanalysis will become an increasingly important tool for evaluating new tests as they become available.
Improving laboratory testing: can we get physicians to focus on outcome?
Authors: Wong E T
Published: January 2020

Managed care is changing the financing of healthcare and replacing open-ended reimbursement with fixed pricing schemes. Clinical laboratory tests will remain an important part of medical practice because laboratory information is essential for diagnosis and management of patients. The relative role of the hospital-based clinical laboratory, however, remains to be determined because healthcare organizations are reevaluating their services and attempting to drive down costs through reducing unit costs, decreasing utilization of services, and improving patient outcomes. The challenge for the clinical laboratory in managed care is to achieve appropriate utilization of laboratory tests so that clinical outcomes are optimized. The clinical laboratory at this medical center has used a number of approaches to improve utilization of thyroid function tests, isoenzyme tests for myocardial infarction, beta-human chorionic gonadotropin tests, and stat laboratory services for the emergency department. These experiences suggest that the laboratory can contribute to optimizing utilization of laboratory tests. This goal will require mutual cooperation of both the clinician and the clinical laboratory physician and (or) scientist.
Multivariate receiver-operating characteristic curve analysis: prostate cancer screening as an example
Authors: Shultz E K
Published: January 2020

The evolution of test performance analysis should include the long-term costs and benefits associated with testing. Evolutionary laboratory techniques to achieve this include introduction of a new methodological technique, a multivariate extension to a current analytical technique, receiver-operating characteristic (ROC) curve analysis (MultiROC analysis). This extension to ROC methodology allows the comparison of composite test rules in a format similar to that of ROC curves. Statistical properties, guidelines for use, and a detailed example are described. MultiROC is used in the outcomes analysis of the value of screening for prostate cancer. The effect of age and different test decision thresholds are examined in an extension of a previously published outcomes analysis. The results indicate that the variations in test performances caused by these components are important in assigning a final cost:benefit ratio of screening for prostate cancer.
Homogeneous immunoassay of whole-blood samples
Authors: Merenbloom B K , Oberhardt B J
Published: January 2020

Proof of principle has been shown for a rapid, quantitative, homogeneous immunoassay capable of analyzing whole-blood samples. The assay was performed with test cards and a small instrument designed for use at the point of care. The immunoassay has an immunological "front end" combined with a coagulation cascade chemistry "back end" and is made possible by combining two patented technologies: (a) a serine protease inhibitor [Porter and Bruhnke, Photochem and Photobiol 1990; 51(1):37] and (b) paramagnetic iron oxide particles (PIOP) in a mixture of buffers and coagulation assay components supplied as a dry film in a test-card reaction chamber [Oberhardt et al., Clin Chem 1991;37:520]. A model steric-hindrance immunoassay based on these technologies was established for the measurement of biotin. The calibration curve was developed by measuring plasma samples supplemented with biotin. The reagents were inhibited biotinylated thrombin, anti-biotin monoclonal antibody, and PIOP.
Analytical and clinical performance goals for testing autoantibodies to thyroperoxidase, thyroglobulin, and thyrotropin receptor
Authors: Feldt-Rasmussen U
Published: January 2020

Methods for measuring thyroid autoantibodies--to thyroperoxidase (TPOAb), thyroglobulin (TgAb), and thyrotropin receptor (TRAb)--have improved over the last decade, but increasingly, accurate and sensitive methods are needed for identifying patients with autoimmune thyroid diseases and individuals at high risk for onset of thyroid autoimmunity. With the increased quality requirements for these methods, it becomes more important to look at the functional sensitivities and precision profiles of the various methods. International standardization in this field is also needed. Because most sera containing human thyroid autoantibodies display a variety of antigen-specific immunoglobulins of different classes and subclasses with different affinity and avidity in their epitope reaction, investigators must decide whether the autoantibodies should be quantified in terms of immunoglobulin content, antigen/epitope reactivity, or binding capacity. Until these problems are solved, the best means for standardization are the Medical Research Council calibrators for TPOAb and TgAb, whereas no standardization exists for TRAb.
Identification and quantification of hemoglobins A, F, S, and C by automated chromatography
Authors: Papadea C , Cate J C
Published: January 2020

The Bio-Rad Variant Hemoglobin Testing System is an automated HPLC analyzer marketed with a Beta-thalassemia Short Program to quantify hemoglobins (Hbs) F and A2 and assist in detecting Hbs A, S, C, D, and E. We evaluated this system to replace several traditional methods for Hb in our hospital laboratory. Analytical performance relevant to quantifying Hbs A, S, C, and F was assessed with blood samples obtained from our local patient population. Studies of precision (CVs < 3%) and analytical limits (% of total Hb) of Hbs A (2-86%), F (1-89%), S (5-90%), and C (3-92%) demonstrated results comparable with or exceeding those of traditional methods. Results for patients' samples (n) for Hbs A (107), F (157), S (128), and C (27) correlated well (r > 0.93) with results by traditional methods. The satisfactory performance and efficiency led us to implement this system for routine quantification of clinically significant Hbs.
Marked interference of hyperglycemia in measurements of mean (red) cell volume by Technicon H analyzers
Authors: van Duijnhoven H L , Treskes M
Published: January 2020

Severe hyperglycemia can result in falsely high results for mean cell (erythrocyte) volume (MCV), which will also cause false results for erythrocyte indices calculated on the basis of MCV. Falsely high MCV results were obtained with the Technicon H1 and H2 analyzers and (to a lesser extent) with the Coulter T660. The H analyzers were more susceptible to this interference than was the Coulter T660. This difference in sensitivity of MCV to hyperglycemia can be explained by the use of sodium dodecyl sulfate in the Technicon erythrocyte diluent and by differences in incubation times. In severe hyperglycemia, results for MCV, mean cell hemoglobin concentration, and hematocrit obtained from electronic cell counters, especially Technicon H systems, are unreliable.
Inhibition of Na,K-ATPase by oleandrin and oleandrigenin, and their detection by digoxin immunoassays
Authors: Jortani S A , Helm R A , Valdes R
Published: January 2020

Ingestion of oleander plant, containing the cardiac glycoside oleandrin, has been reported to induce fatal poisonings. Derivatives of oleandrin are structurally similar to digoxin. We investigated the cross-reactivities of oleandrin and its aglycone metabolite, oleandrigenin, in several commercially available digoxin immunoassays; assessed their ability to inhibit Na,K-ATPase catalytic activity; and measured their binding to proteins in serum. As assayed with ACS:180, Stratus, RIA, On-Line, and TDx digoxin assays, oleandrin at 100 micromol/L in digoxin-free serum gave apparent digoxin values of 0, 0.83, 2.24, 2.37, and 5.34 nmol/L, respectively, whereas oleandrigenin at that concentration gave results of 0, 0.52, 0.77, 4.94, and 1.40 nmol/L. Study of Na,K-ATPase inhibition showed IC50 values (micromol/L) of 0.22 for ouabain, 0.62 for oleandrin, 1.23 for oleandrigenin, and 2.69 for digoxin. At 25 degrees C, 96% of oleandrin and 48% of oleandrigenin were bound to serum proteins. Because detection of oleandrin and oleandrigenin by digoxin immunoassays is variable between assays as well as between congeners, assessment of cross-reactivity is warranted for each assay. The inhibition of Na,K-ATPase by oleandrin and oleandrigenin confirms that they likely exert their toxic effects through inhibition of sodium pump activity. In cases of digitalis-like poisoning with suspicion of oleander ingestion, a combination of digoxin immunoassays may be useful to effectively rule out the presence of oleander.
Performance evaluation of automated immunoassays on the Technicon Immuno 1 system
Authors: Letellier M , Lévesque A , Daigle F , Grant A
Published: January 2020

We performed an immunoassay evaluation for various analytes on a fully automated random-access analyzer, the Technicon Immuno 1 system from Bayer Corp. This system involves latex agglutination, magnetic separation sandwich, and magnetic separation competitive immunoassay configurations. The evaluated analytes were thyrotropin (TSH), triiodothyronine, thyroxine, free thyroxine, follitropin, lutropin, prolactin, beta subunit of human chorionic gonadotropin, cortisol, ferritin, alpha-fetoprotein, carcinoembryonic antigen, and prostate-specific antigen. We tested the assay precision, linearity, and correlation with comparison methods for these analytes. The functional sensitivity of the TSH assay and the sample-to-sample carryover were also studied. Excellent results were obtained for within-run and between-day precision studies, with most assays showing within-run CVs <4% and between-day CVs <6%. The linearity for all assays was acceptable and the correlation between Immuno 1 assays and comparison methods showed satisfactory results. The functional sensitivity of the TSH assay was estimated at 0.04 mU/L. No sample-to-sample carryover was detected.
Effect of salt intake on excretion of endogenous ouabain-like substance, measured by RIA
Authors: Semra Y K , Butt A N , Swaminathan R
Published: January 2020

Recent studies suggest that ouabain or a ouabain-like substance (OLS) may be present endogenously in humans. We developed a RIA for ouabain with antisera raised in goat against ouabain conjugated to keyhole limpet hemocyanin and ovalbumin. The antiserum was of high antibody titer (200,000) and was specific for ouabain, with little cross-reactivity with common steroids and structurally related compounds such as ouabagenin (4%), strophanthidin (4%), and dihydroouabain (2%). The RIA had a working range of 0.06-2.0 nmol/L, and the intra- and interassay CV was 6.5% at a concentration of 1.7 nmol/L. With this assay the effect of salt loading on urinary excretion of OLS was examined in 10 healthy volunteers (ages 18-22 years) who increased their salt intake (sodium) for 5 days and reduced it for the next 5 days. Urine was collected and OLS concentration was measured by RIA after solid-phase extraction with a Bond Elut C18 column. Excretion of OLS and sodium were maximal on day 5 and lowest on days 9 and 10. Urine excretion of OLS on day 5 (2.66 +/- 1.22 nmol/24 h) was significantly higher (P < 0.0001) than on day 10 (1.47 +/- 0.69 nmol/24 h). We conclude that (a) the assay developed has sufficient sensitivity and specificity to detect endogenous OLS present in biological fluids, and (b) salt intake increases the excretion of OLS.
Spectrophotometric determination of urinary iodine by flow-injection analysis with on-line catalytic digestion
Authors: Yaping Z , Dongxing Y , Jixiang C , Tianshiu L , Huiqin C
Published: January 2020

A flow-injection technique involving on-line catalytic digestion and spectrophotometric detection has been developed for the determination of iodine in urine. After urine samples are digested by KMnO4-K2Cr2O7-H2SO4 solution, the iodine in the urine catalyzes the reaction of As(III) with Ce(IV). The remaining Ce(IV) is then reacted with brucine and the product is detected with a spectrophotometer at 480 nm. With this technique, we obtained a detection limit for urinary iodine of 0.039 mumol/L, and the linear range was 0.039-7.88 mumol/L with a CV < 3%. Analytical recovery ranged between 92% and 104% (mean 99%). The sampling frequency of the flow-injection technique was 70/h. We applied the method to measure the iodine concentration in a freeze-dried urine reference sample and in collected urine samples, and compared the results with those obtained by the accepted alkaline ashing technique. The proposed technique has the advantages of being simple, rapid, precise, accurate, and sensitive. It can be used to assess iodine-deficient populations as well as those receiving treatment.
Assay of plasma homocysteine: light sensitivity of the fluorescent 7-benzo-2-oxa-1, 3-diazole-4-sulfonic acid derivative, and use of appropriate calibrators
Authors: Dudman N P , Guo X W , Crooks R , Xie L , Silberberg J S
Published: January 2020

The recognition of homocysteine as a vascular risk factor has led to increased clinical interest in assaying plasma homocysteine concentrations. Our aim was to improve the reliability of a widely used assay based on HPLC of the fluorescent 7-benzo-2-oxa-1, 3-diazole-4-sulfonic acid (SBD) derivative. We found that SBD derivatives of homocysteine, cysteine, and N-acetylhomocysteine were highly unstable in light but essentially stable in the dark for several hours at either 0 degree C or 25 degrees C. As our primary calibrator, we chose homocystine added to human serum for more consistent results than homocysteine or homocystine in an aqueous buffer. N-acetylcysteine was effective as an internal recovery standard. We observed a previously unreported peak with a prolonged elution time in some plasma samples from subjects who had ingested methionine. Our findings suggest improvements in this and other assay procedures for plasma homocysteine.
Cerebrospinal fluid and plasma distribution of myo-inositol and other polyols in Alzheimer disease
Authors: Shetty H U , Holloway H W , Schapiro M B
Published: January 2020

Previous studies suggest the presence of increased concentrations of cerebral myo-inositol in Alzheimer disease (AD). To characterize this abnormality further, we quantified myo-inositol and several other polyols in cerebrospinal fluid (CSF) and plasma from 10 AD subjects and 10 healthy age-matched controls by using a gas chromatographic-mass spectrometric technique. The mean CSF concentration and CSF/plasma concentration ratio of myo-inositol in AD were not significantly different from those determined in control subjects. Also, concentration profiles of other polyols were not significantly altered in AD. CSF and plasma myo-inositol concentrations were correlated in control subjects but not in AD subjects. However, a significant correlation between CSF and plasma 1,5-anhydrosorbitol (a polyol internal control) concentrations observed in control subjects was retained in AD subjects.
Heteroduplex generator in analysis of Rh blood group alleles
Authors: Stoerker J , Hurwitz C , Rose N C , Silberstein L E , Highsmith W E
Published: January 2020

We describe the use of heteroduplex analysis to enhance the resolution of different rhesus-derived (Rh) isotypes. Heteroduplex analysis of different domains of the Rh D and Rh CE loci can be performed to diagnose a variety of blood group incompatibilities. One application of this technique is the ability to test for fetal-maternal blood group incompatibilities during pregnancy. Several new serotype-specific sequence variations were discovered in the mapping of the Rh locus, and used in the construction of artificial heteroduplex generators (HGs). HGs facilitate the resolution of the Rh isotypes by electrophoretic methods.
Sandwich ELISA for glutathione S-transferase Alpha 1-1: plasma concentrations in controls and in patients with gastrointestinal disorders
Authors: Mulder T P , Peters W H , Court D A , Jansen J B
Published: January 2020

Class Alpha glutathione S-transferases (GST-Alpha) are found in high concentrations in human liver. Increased plasma concentrations of GSTA1-1, the most abundant isoform of GST-Alpha, are a very sensitive marker for hepatocellular leakage. A sandwich-type ELISA was developed, based on a monoclonal antibody specific for human GSTA1-1 and a polyclonal rabbit anti-human GST-Alpha antiserum. The assay is specific for human GSTA1-1, and has a detection limit of 0.04 micrograms/L. The distribution of plasma GSTA1-1 concentrations in 350 blood donors was nearly normalized by logarithmic transformation and an upper normal reference concentration of 5.9 micrograms/L was calculated. Men had significantly higher plasma GSTA1-1 concentrations than women (P <0.0001). In women, but not in men, a significant increase was noted with age (P <0.05). In patients with inflammatory bowel disease (n= 210), gastrointestinal tumors (n= 70), irritable bowel disease (n= 36), or chronic pancreatitis (n= 12), plasma GSTA1-1 concentrations were similar to those of controls. In contrast, plasma GSTA1-1 concentrations were increased to a similar extent as alanine aminotransferase activities in patients with liver disorders (n= 37).
Low-density lipoprotein susceptibility to in vitro oxidation in healthy smokers and nonsmokers
Authors: Siekmeier R , Wülfroth P , Wieland H , Gross W , März W
Published: January 2020

We analyzed the susceptibility of low-density lipoproteins (LDL) to oxidation in 17 healthy smokers (43.3 +/- 16.8 pack-years) and 19 healthy nonsmokers, matched for age (smokers: 52 +/- 7 years; nonsmokers: 53 +/- 7 years), gender, and relative body mass. Cholesterol, triglycerides, LDL cholesterol, HDL cholesterol, and apolipoprotein (apo) B were not different between smokers and nonsmokers; apo A-I was slightly lower in smokers (one-tailed P = 0.066). To study whether LDL from smokers were prone to in vitro oxidation than LDL from nonsmokers, we measured the time kinetics of diene formation and the production of malondialdehyde during oxidation of LDL in vitro. In smokers and nonsmokers, respectively, the mean (+/-SD) lag times (tinh) of diene formation were 111 +/- 26 and 100 +/- 27 min, the peak rates of diene formation (Vmax) were 5.99 +/- 2.34 and 6.34 +/- 2.30 mmol x min-1 x g-1, and the amounts of dienes produced during the propagation phase (dmax) were 250 +/- 264 and 248 +/- 56 mmol x g-1. Neither the malondialdehyde content of LDL (measured as thiobarbituric acid-reactive substances) before oxidation nor the amount of malondialdehyde generated during oxidation (smokers: 57.0 +/- 14.2 micromol x g-1; nonsmokers: 63.2 +/- 15.2 micromol x g-1 indicated any statistically significant effect of smoking. When nonsmokers and smokers were considered together, the amount of malondialdehyde generated during oxidation correlated with age (nonparametric rs = 0.405), body mass index (r2 = 0.573), and concentrations of apo B (rs = 0.480), cholesterol (rs = 0.448), triglycerides (rs = 0.436), and LDL cholesterol (rs = 0.398). Our data show that smoking is not associated with increased oxidizability of LDL in healthy men and women at ages 42-63 years.