bluuebunny/crossref_metadata_2025 huggingface dataset:
An enzymatic method for oxalate automated with the Cobas Fara centrifugal analyzer.
Authors: Allen L C , Kadijevic L , Romaschin A D
Published: January 2020

Measurement of oxalate in urine has been automated for use with the Cobas Fara centrifugal analyzer. No sample pretreatment other than (a critical) pH adjustment is required. Between-run CVs were less than 4%. Results were linearly related to oxalate concentration to 1000 mumol/L. Ascorbic acid ingestion, up to 5 g of ascorbate daily, caused no demonstrable interference with the assay. This practical, automated method for assaying urinary oxalate is substantially faster than other chemical or enzymatic methods.
Versatile, efficient system for extracting drugs from urine for gas chromatographic/mass spectrometric analysis.
Authors: Brooks K E , Smith N B
Published: January 2020

This is a method for efficiently extracting a wide variety of drugs from urine for toxicological analysis by gas chromatography/mass spectrometry. Before extraction, the urine sample is acetylated, diluted with an equal volume of water, and saturated with NaCl. This solution is then mixed with an equal volume of dichloromethane/acetone (2:1 by vol). The organic (top) phase is aspirated and evaporated, and the residue is redissolved in a suitable solvent for injection or further derivatization. This procedure is suitable for all drugs except carboxylate-containing drugs, which may be isolated by replacing the acetylation step with acidification of the urine to pH 2. Studies with 16 drugs containing amino, amide, alcoholic hydroxyl, phenolic hydroxyl, carboxylate groups, or combinations thereof, showed that all drugs except theophylline and benzoylecgonine were extracted with analytical recoveries ranging from 70% to 100%.
Extending the detection limit of the TDx fluorescence polarization immunoassay for benzoylecgonine in urine.
Authors: de Kanel J , Dunlap L , Hall T D
Published: January 2020

This modified calibration method decreases from 300 to 27 micrograms/L the limit of detection for the cocaine metabolite (hydrolysis product), benzoylecgonine, by the Abbott Laboratories TDx fluorescence polarization immunoassay. For this determination we used 30 controls prepared from a single urine pool known to be negative for cocaine metabolite. Assay of 80 controls prepared from 20 different patients' urine samples yielded a limit of detection of 44 micrograms/L. To test these limits of detection, we analyzed 90 patients' urine samples known to be negative for cocaine metabolite and 74 patients' samples known to be positive for cocaine metabolite, using the TDx with our revised calibration. Results for two of the known negative samples and 96% of the samples containing cocaine in the 50 to 100 micrograms/L range fell above the 44 micrograms/L limit. The TDx showed excellent calibration stability. For 28 days during the test, the instrument was not recalibrated. During this period the day-to-day analysis of 50 micrograms/L controls produced a mean TDx response of 0.485 (SD 0.007) with a coefficient of variation of 1.5%.
Molecular genetics and the transformation of clinical chemistry.
Authors: Williamson R
Published: January 2020

Clinical chemistry is going through an identity crisis, squeezed between automation (de-skilling) on the service side and molecular genetics in research. Automated routine estimations are now carried out and interpreted by machines; the skilled staff members required are more likely to have degrees in electronics than medicine or biochemistry. The role of molecular genetics is more ambiguous; it is inherently reductionist, in that it attempts to explain most clinical phenomena in terms of DNA sequence alone. This has been remarkably successful for single-gene defects (such as those causing Duchenne muscular dystrophy, hemoglobinopathies, cystic fibrosis, and ataxias) and may well prove equally so for Alzheimer's disease, cancer, heart disease, and schizophrenia. DNA diagnosis is not yet routine, but because of technical advances such as gene amplification ("PCR") and high-sensitivity gene-detection assays, it may soon become so, not only in major centers but also in local pathology laboratories and general practice. Clinical chemists must decide whether they wish to respond to this new and stimulating challenge by retooling and retraining. Should anyone be permitted into clinical chemistry during the 1990s without knowledge of both electronics and molecular genetics? Will there be a clinical chemistry in the twenty-first century other than through molecular genetics? This article is a personal response to these questions.
Determination of alpha 2-macroglobulin-trypsin complex with a new synthetic substrate.
Authors: Kuroiwa K , Nakatsuyama S , Katayama K , Nagasawa T
Published: January 2020

We have developed a colorimetric assay for quantifying alpha 2-macroglobulin-trypsin complex (alpha 2M-TRY) in human serum, based on use of a new chromogenic substrate D-gamma-tert-butyloxy-Glu-Gly-Arg-3-carboxy-4-hydroxyanilide dihydrochloride (PS-3001). Within-run CVs by this assay were 4.76%, 1.57%, and 0.83% for trypsin complex concentrations of 3.1, 12.2, and 48.1 U/L, respectively (n = 10 each). Between-day CVs were 5.38%, 3.12%, and 2.20% at each concentration, respectively (n = 7). Mean analytical recoveries of alpha 2M-TRY added to serum were 100%, 105%, and 101% for 9.2, 15.1, and 46.3 U/L, respectively (n = 2). The standard curve obtained was linear up to 330 U/L. We applied this method to the study of alpha 2M-TRY activity in sera from 97 healthy subjects (group 1), from 27 patients with acute pancreatitis (group 2), and from 25 patients with other chylopoietic diseases (group 3); results ranged from 0 to 1.2 U/L (mean = 0.5, SD = 0.3), from 1.2 to 77.4 U/L (mean = 14.6, SD = 19.0), and from 0 to 1.3 U/L (mean = 0.4, SD = 0.3), respectively. Concentrations of enzymatically active alpha 2M-TRY were significantly greater in sera from group 2 than in groups 1 and 3. The determination of serum alpha 2M-TRY activity by this simple, rapid, colorimetric method may be useful for the diagnosis and evaluation of pancreatic disease.
Characteristics of creatine kinase-MB and MB isoforms in serum after reperfusion in acute myocardial infarction.
Authors: Christenson R H , Ohman E M , Clemmensen P , Grande P , Toffaletti J , Silverman L M , Vollmer R T , Wagner G S
Published: January 2020

Characteristics of CK-MB, the MB1 and MB2 isoforms, and the MB2/MB1 ratio are described in six acute myocardial infarction (AMI) patients in whom the infarct-related artery was identified and, after intervention, normal coronary flow was re-established. After myocardial reperfusion, washout of CK-MB and the MB2 isoform occurred in parallel, with CK-MB peaking between 5.75 and 10.0 h, and MB2 peaking between 4.50 and 8.00 h. In five of the six patients, MB1 peaked between 8.75 and 15.5 h; the MB2/MB1 ratio demonstrated the earliest peak from 0.75 to 2.25 h. When we compared this study group to an additional 10 AMI patients who had achieved myocardial reperfusion earlier, we found a significant difference (P less than 0.005) for all tests, except MB1 isoform activity, as early as 50 min after reperfusion. This same comparison, by logistic-regression analysis, showed that the MB2/MB1 ratio discriminated between the groups 50 min after reperfusion (P less than 0.05); MB2 showed near-significance at 100 min (P less than 0.057); and CK-MB achieved significance after 200 min (P less than 0.05). CK-MB, the MB2 isoform, and especially the MB2/MB1 ratio show potential for the early, noninvasive detection of myocardial reperfusion.
Automated DNA sequencing methods involving polymerase chain reaction.
Authors: McBride L J , Koepf S M , Gibbs R A , Salser W , Mayrand P E , Hunkapiller M W , Kronick M N
Published: January 2020

Polymerase chain reaction (PCR) as a method for preparing DNA templates has been used for several DNA sequencing applications. An in situ procedure for directly sequencing PCR products by the dideoxy-termination method has been developed by using fluorophore-labeled sequencing primers. Completed sequence reactions were combined and loaded into a single electrophoretic lane of a fluorescence-based DNA sequence analyzer. DNA targets devoid of a universal primer sequence could be sequenced with labeled universal primers by incorporating a universal primer sequence into the PCR product. With this method, the sequence of a 351-bp region in the bacteriophage lambda genome was fully analyzed in a single lane with automatic base identification accuracy of greater than 99%. An unknown sequence, 1.7 kb long, also was sequenced by this procedure, in combination with a "PCR gene walking" strategy. Comparison of the 1110 bases in overlapping sequence data from both strands yielded only two single-base ambiguities. Automated DNA sequence analysis of the highly polymorphic HLA-DQA-1 (alpha) region in the human genome can be performed with this simple methodology. Use of this PCR-sequencing method to analyze DNA extracted from a one-month-old blood sample from an individual who is heterozygous at this locus allowed unambiguous assignment of genotype.
Enzymatic assay of magnesium through glucokinase activation.
Authors: Fossati P , Sirtoli M , Tarenghi G , Giachetti M , Berti G
Published: January 2020

We describe an improved enzymatic method for assaying magnesium in serum, plasma, or urine. Magnesium participates as an Mg.ATP complex in a reaction catalyzed by glucokinase (EC 2.7.1.2) coupled to an NADP+-dependent glucose-6-phosphate dehydrogenase (EC 1.1.1.49) reaction. The increase of absorbance at 340 nm, due to the NADPH produced, is proportional to the amount of the activated glucokinase, which in turn is related to the concentration of magnesium in the sample. The method is characterized by a zero-order reaction kinetics, affording a simple and rapid assay with good sensitivity and linearity (up to 2.06 mmol/L) and by working solutions that are stable (refrigerated) for one month. The method is reliable, produces test results that compare closely with those of the atomic absorption spectrophotometry (r greater than or equal to 0.99), is suitable for routine work, and lends itself to automation.
Decreased dehydroepiandrosterone sulfate in pigmented nodular adrenal dysplasia.
Authors: Braithwaite S S , Collins S , Prinz R A , Walloch J L , Winters G L
Published: January 2020

Previous reports on patients with endogenous Cushing's syndrome describe low concentrations of the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S) in adrenal adenoma and in a case of feminizing macronodular hyperplasia. Here we present hormonal data from two adult sisters with Cushing's syndrome as a result of pigmented nodular adrenal dysplasia. Corticotropin concentrations were in the mid-normal range, cortisol production was unaffected by administration of dexamethasone (8 mg/24 h), and baseline concentrations of DHEA-S were less than 0.5 mumol/L. A low concentration of DHEA-S in these and other previously reported patients with Cushing's syndrome correctly predicts the results of dynamic testing. Decreased DHEA-S in a patient with endogenous Cushing's syndrome can be ascertained by assay of a single sample and should prompt consideration of the diagnosis of autonomous bilateral nodular disease as well as adrenal adenoma.
Simple enzymatic determination of total cholesterol in gallstones.
Authors: Wei J S , Huang H M , Shyu W C , Wu C S
Published: January 2020

In this simple method for rapid enzymatic determination of total cholesterol in human gallstones, gallstone powder is dissolved in an 80/20 by vol mixture of N,N-dimethylformamide and dimethyl sulfoxide and reacted directly with the aqueous enzymatic reagent, without further treatment. The organic solvents do not interfere with enzymatic activities of cholesterol oxidase, esterase, and peroxidase in the assay mixture. The method is reproducible (CVs 3.7% to 6.6%), analytical recoveries ranged from 98.6% to 102%, and linearity is good. Furthermore, results correlated well with those obtained by infrared spectroscopic measurements.
Macroenzymes: biochemical characterization, clinical significance, and laboratory detection.
Authors: Remaley A T , Wilding P
Published: January 2020

"Macroenzymes" are enzymes in serum that have formed high-molecular-mass complexes, either by self-polymerization or by association with other serum components. Many enzymes in serum that are measured in clinical chemistry laboratories can occur in a macroenzyme form. Macroenzymes are interesting clinically because of their association with several diseases, including autoimmune diseases and liver disease, and are being investigated as possible diagnostic markers. Most importantly, macroenzymes frequently interfere with the interpretation of serum enzyme results, and as a result can cause diagnostic and therapeutic errors. We review the biochemical characterization, clinical significance, and laboratory detection of macroenzymes.
Steroid profile for urine: reference values.
Authors: Weykamp C W , Penders T J , Schmidt N A , Borburgh A J , van de Calseyde J F , Wolthers B J
Published: January 2020

We describe a project, participated in by 24 institutions in The Netherlands and Belgium, to determine normal reference values for steroids in urine by capillary gas chromatography. Urine samples from 288 healthy volunteers were analyzed in triplicate. Reference values, expressed in mumol/24 h, were determined for androsterone, etiocholanolone, dehydroepiandrosterone, 11-keto-androsterone, 11-keto-etiocholanolone, 11-hydroxyandrosterone, 11-hydroxyetiocholanolone, pregnanediol, pregnanetriol, 11-desoxytetrahydrocortisol, tetrahydrocortisone, tetrahydrocortisol, allo-tetrahydrocortisol, and 17-keto- and 17-hydroxysteroids. We also determined reference ratios for etiocholanolone/androsterone, tetrahydrocortisone/tetrahydrocortisol, and tetrahydrocortisol/allo-tetrahydrocortisol; an upper limit of a discriminant function to establish polycystic ovarian disease; and reference values for 24-h urine volume and creatinine excretion. Reference values were determined separately for men and women, each in six age categories: 0-3 months, 4 months-12 years, 13-16 years, 17-50 years, 51-70 years, and older than 70 years. We conclude that these reference values are reliable and form a basis for quantitative interpretation of steroid profiles.
Free 3-methoxy-4-hydroxyphenylglycol determined in plasma by liquid chromatography with coulometric detection.
Authors: Hariharan M , VanNoord T , Cameron O G , Curtis G C , Ostrow D G
Published: January 2020

We describe a simple "high-performance" liquid-chromatographic method for determining free 3-methoxy-4-hydroxyphenylglycol (MHPG) in plasma, with coulometric detection and with 4-methoxy-3-hydroxyphenylglycol (iso-MHPG) as the internal standard. MHPG and iso-MHPG are extracted from plasma into ethyl acetate and the extract is washed with a sodium bicarbonate solution, evaporated, reconstituted, and injected into a 25 x 0.4 cm column packed with 3-micron particles of C18 material. We used a mobile phase of acetate buffer (100 mmol/L, pH 5.0) and methanol (92:8 by vol) and an oxidation voltage of 0.5 V. The detection limit of the assay is 0.1 micrograms/L. The interassay CV for a sample with a mean MHPG concentration of 3.84 micrograms/L was 5.2%. The average absolute recovery for the method was 37%.
Heterogeneity of serum creatine kinase isoenzyme MM in myocardial infarction: clinical significance and post-synthetic conversion of "abnormal" sub-bands.
Authors: Williams J , Williams K M , Marshall T
Published: January 2020

We investigated the "abnormal" sub-bands of serum creatine kinase (CK; EC 2.7.3.2) isoenzyme MM in acute myocardial infarction (AMI), using isoelectric focusing in polyacrylamide gels, and compared the patterns with those for non-AMI patients and for athletes with increased CK. The "abnormal" sub-bands a (pI 7.55), b (pI 7.35), c (pI 7.25), d (pI 7.05), e (pI 6.85), f (pI 6.72), g (pI 6.50), h (pI 6.40), i (pI 6.28), j (pI 6.20), and k (pI 6.15), in common with "normal" sub-bands 1 (pI 6.91), 2 (pI 6.65), and 3 (pI 6.35), were less uniformly distributed in the AMI and demonstrated a faster rate of anodal conversion than in the non-AMI patients and athletes. "Abnormal" sub-bands a and b were detected only in the AMI patients. Incubation of myocardial CK-MM, predominantly CK-MM 1, with 2-mercaptoethanol, 15 mmol/L, resulted in conversion to the "abnormal" sub-bands b and c. Incubation of myocardial CK-MM with normal serum of low total CK yielded CK-MM 3, which on further incubation with 2-mercaptoethanol, 15 mmol/L, resulted in conversion to the "abnormal" sub-bands f and g. Comparable in vitro incubation of serum from AMI patients gave pattern changes consistent with conversion of CK-MM 1 to b, c; CK-MM 2 to d, e; and CK-MM 3 to f, g.
Optimized microturbidimetric assay for fibrinogen.
Authors: Macart M , Koffi A , Henocque G , Mathieu J F , Guilbaud J C
Published: January 2020

In this assay we measure the turbidity produced by precipitation of plasma fibrinogen with a reagent composed of ammonium sulfate, EDTA, and guanidine hydrochloride. The two-step reagent addition, and use of fixed reaction times, eliminates interference from bilirubin, hemoglobin, and chylomicrons. We checked 135 monoclonal proteins for interference, finding the probability of encountering major interference in samples from adults to be very low, P = 0.0002. The method is calibrated with purified fibrinogen and the response is linear over the range 0-10 g/L. Within-run precision (CV) is less than 2% from 1 to 10 g/L. Correlations with the immunoturbidimetric (r = 0.99), chronometric (r = 0.99), and clotting (r = 0.97) methods were extremely high.
Nonenzymatic stopped-flow fluorimetric method for direct determination of uric acid in serum and urine.
Authors: Pérez-Bendito D , Gómez-Hens A , Gutiérrez M C , Antón S
Published: January 2020

A simple, direct, sensitive, and selective stopped-flow method for the fluorimetric determination of uric acid in serum and urine samples is described. The variation of fluorescence intensity during the reaction between uric acid and 1,1,3-tricyano-2-amino-1-propene (triap) in the presence of hydrogen peroxide is monitored. For these kinetic measurements peroxide is monitored. For these kinetic measurements we used a versatile stopped-flow module that can be fitted to any fluorimeter. The linear range of the proposed method is 0.08-3.00 mg of uric acid per liter, and the detection limit is 0.03 mg/L. Within- and between-assay CVs and selectivity data are reported. Results for serum and urine samples correlated well with those obtained by the uricase method The proposed method is inexpensive and requires no sophisticated detection equipment.
Measurement of autoimmune response against collagen types I, III, and IV by enzyme-linked immunosorbent assay, and its application in infective endocarditis.
Authors: De Buyzere M L , De Scheerder I K , Delanghe J R , Robbrecht J H , Clement D L , Wieme R J
Published: January 2020

In these enzyme-linked immunosorbent assays for determination of autoantibodies (IgG, IgM) against collagen type I (ACA I), III (ACA III), and IV (ACA IV), we use commercially available antigen preparations. Inhibition curves showed limited cross-reactivity between these different collagen preparations, the major interference being observed after addition of collagen type III in the ACA I procedures. Imprecision (CVs) for high- and low-titer samples ranged between 1.5% and 7.9% (within-run) and 5.5% and 12.7% (between-run) for ACA I, between 2.2-8.7% and 4.5-10.7% for ACA III, and between 1.3-5.9% and 7.4-11.6% for ACA IV. Significantly increased humoral immune response against collagen types I and III (P less than 0.001) could be demonstrated during the first month of infective endocarditis. In contrast, only borderline increases, however constant, of autoimmune response against basement-membrane collagen (ACA IV) were noticed during 90 days of follow-up.
A dual-precipitation method evaluated for measurement of cholesterol in high-density lipoprotein subfractions HDL2 and HDL3 in human plasma.
Authors: Patsch W , Brown S A , Morrisett J D , Gotto A M , Patsch J R
Published: January 2020

The dual-precipitation method for measurement of cholesterol in high-density lipoprotein subfractions HDL2 and HDL3 (Warnick et al., Clin Chem 1982;28:1574) was compared with quantification of cholesterol in HDL2 and HDL3 by zonal ultracentrifugation (Patsch et al., J Lipid Res 1974;15:356-66). For 39 plasma specimens differing widely in their HDL subfraction cholesterol concentration, the coefficient of correlation between the two methods was 0.94 for HDL2-cholesterol, 0.82 for HDL3-cholesterol. Storage of plasma specimens at -70 degrees C decreased the apparent content of HDL3-cholesterol by 5%; no significant changes in HDL2-cholesterol were observed. In frozen plasma, interference by apoB-containing lipoproteins and by lipoprotein(a) was negligible. Mean weight ratios of apoA-I to cholesterol were twice as high for HDL3 as for HDL2, reflecting the increased cholesterol content of HDL2. The study suggests that quantification of HDL2 and HDL3 cholesterol by precipitation is appropriate for use in epidemiological studies.
Homogentisic acid determined in biological fluids by HPLC.
Authors: Bory C , Boulieu R , Chantin C , Mathieu M
Published: January 2020

In this rapid, specific, and sensitive high-performance liquid-chromatographic method of analysis for homogentisic acid in biological fluids, homogentisic acid is separated on a column of Nucleosil CN. This method, which we applied to the diagnosis of three cases of alcaptonuria, represents a suitable analytical tool for the diagnosis of alcaptonuria.
Factitiously high sodium activities on the Ektachem 400 owing to interferences by high gamma-globulin concentrations.
Authors: Eastep S J , Benson P J , Preese L M , Apple F S
Published: January 2020

Sera from patients with above-normal gamma-globulin concentrations give sodium values as much as 10% higher when measured in the Kodak Ektachem 400 analyzer than results obtained with the Beckman Astra-8 analyzer. Results obtained with the Astra were in agreement with flame photometry. A similar relative bias was observed for potassium measurement in the Ektachem. This discrepancy was corrected when we used a new generation of reference fluid provided by Kodak, which is currently available for general use.
D-lysine effectively decreases the non-enzymic glycation of proteins in vitro.
Authors: Sensi M , Pricci F , De Rossi M G , Morano S , Di Marlo U
Published: January 2020

Excessive non-enzymic glycation of proteins alters their physicochemical properties, with possible pathological effects. We investigated the in vitro inhibition of protein glycation by D-lysine--an isomer not incorporated into mammalian proteins but possessing the same chemical characteristics as L-lysine. Glucose incorporation was studied as follows: (a) human albumin, IgG, collagen, and isolated glomerular basement membrane were incubated for 20 days with D-glucose (5.0, 10.0, and 20.0 mmol/L) in the presence of D-lysine at 1/10 the sugar concentration; (b) albumin was incubated in similar glucose concentrations but with a constant amount (2.0 mmol/L) of D-lysine; (c) albumin and IgG were incubated for 10 days in buffer containing glucose (10 mmol/L) and increasing concentrations of D-lysine (0.25, 0.5, 1.0, 2.0, and 4.0 mmol/L); (d) inhibition specificity was tested by treating albumin as in c but with glycerol present rather than D-lysine. In addition, we measured ketoamine after incubating albumin (50 g/L) in 10 mmol/L glucose for 10 days in the presence of D-lysine (0.25, 0.5, 1.0, and 2.0 mmol/L). The results show that (a) the amount of glucose bound to the four proteins was significantly (P less than 0.05) decreased in the presence of D-lysine at the higher concentrations of glucose; (b) the lower the glucose concentration, the higher was the inhibitory effect of D-lysine; (c) the inhibition of glucose incorporation into proteins correlated directly with the concentration of D-lysine; (d) no inhibition was observed with glycerol. Ketoamine decreased with increase in D-lysine (P less than 0.01). The effective diminution of non-enzymatic glycation by D-lysine highlights its potential use in vivo.
Measurement of urinary leukotrienes by reversed-phase liquid chromatography and radioimmunoassay.
Authors: Tagari P , Ethier D , Carry M , Korley V , Charleson S , Girard Y , Zamboni R
Published: January 2020

Leukotriene (LT) E4, an important LT metabolite appearing in urine, can be rapidly separated from normal and pathological urines by automated reversed-phase HPLC after a simple sample-processing. The recoveries of LTE4 afforded by this system (86.4 +/- 6.5%, mean +/- SEM for 60 ng/L, 85.4 +/- 0.3% for 200 ng/L) are superior to those obtained by a manual extraction method. Consistency of results is similar. Highly reproducible retention times combined with a radioimmunoassay allow one to identify (based on co-elution) and quantify as little as 8 ng/L LTE4 in a 10-mL urine sample. LTE4 concentrations in urine from healthy persons approach this value (17 +/- 5 ng/L), whereas samples from patients with cardiac ischemia show a wider range of concentrations (8 to 388 ng/L), up to 50 times the detection limit. Thus this method is applicable to the noninvasive investigation of leukotriene involvement in a wide range of ischemic, inflammatory, and hypersensitive conditions.
Diagnostic value of measuring pancreatic lipase and the P3 isoform of the pancreatic amylase isoenzyme in serum of hospitalized hyperamylasemic patients.
Authors: Panteghini M , Pagani F
Published: January 2020

We assayed amylase (AMY) isoenzymes by cellulose acetate electrophoresis and determined pancreatic lipase (LPS) activity by a turbidimetric colipase-supplemented method in 54 hospitalized hyperamylasemic patients (32 men and 22 women; mean age 61.5, SD 16, years). In AMY isoenzyme analysis, use of a value for P3 isoform greater than 14 U/L as a positive test for acute pancreatitis gave a diagnostic efficiency of 92.6%, a predictive value of a positive test result of 90.5%, and a predictive value of a negative test of 100%. Four of 12 patients with other, nonpancreatic abdominal diseases had false-positive test results. LPS activity (cutoff limit, 700 U/L) was as effective as P3 isoform in distinguishing patients with acute pancreatitis (sensitivity, 100%) from those without acute pancreatitis (specificity, 81.3%). Thus, P3 isoform and LPS appear to be interchangeable markers of pathological release of pancreatic enzymes into the bloodstream during acute pancreatitis. This finding decreases the need for the expensive radiological procedures currently required to confirm this diagnosis. In particular, negative results virtually exclude acute pancreatitis.
Correlation between heart disorders and concentrations of directly measured atrial natriuretic peptide in plasma.
Authors: Fridrich L , Szekeres T , Hartter E , Schweighofer F , Gassner A , Laczkovic A
Published: January 2020

We used new commercially available direct radioimmunoassay to measure human atrial natriuretic peptide (h-ANP) in plasma from 48 individuals who were being evaluated for left and right ventricular function. For 13 healthy individuals with normal ventricular function these concentrations ranged up to 54 ng/L. Measurements of h-ANP clearly differentiated between normal subjects, patients with coronary artery disease, and patients who had undergone orthotopic heart transplantation (ANOVA P less than 0.0001, significant differences between all groups)--all showing normal ventricular function at rest. There was a strong negative correlation (r = -0.64, P less than 0.001) between left ventricular ejection fraction and h-ANP concentrations in plasma of patients with proven coronary artery disease, patients with cardiomyopathy, and healthy individuals. Results by the present method and methods involving extraction of the sample correlated well. Evidently the direct assay of h-ANP in plasma yields information that could be used to help evaluate heart disorders and other pathophysiological conditions causing increased h-ANP concentrations in plasma.
Concordance of creatine kinase-MB activity and mass.
Authors: Eisenberg P R , Shaw D , Schaab C , Jaffe A S
Published: January 2020

The recent availability of monoclonal antibodies that are highly specific for creatine kinase (CK; EC 2.7.3.2) MB isoenzyme should allow for the development of rapid, sensitive, and specific assays of CK-MB mass and activity. However, the relationship between the mass concentration of CK-MB and its activity in plasma has previously been thought by some to be variable. To determine the extent to which discrepancies of potential clinical significance might arise between measurements of activity and mass in plasma, we compared CK-MB activity and concentration in 1298 samples obtained from 226 patients admitted to the cardiac-care unit. CK-MB activity concentration was determined with an immunoadsorption assay, and mass concentration was measured by an automated "sandwich" assay (Magic Lite; Ciba Corning Diagnostics). Both of these assays are based on specific monoclonal antibodies for CK-MB. Values obtained with these assays correlated well (r = 0.94). Normal and abnormal values with the two assays were concordant in 96% of the samples. In all but three instances, differences occurred late after myocardial infarction and were characterized by minimal increases as determined by one method vs values at the upper limit of normal as determined with the other. Thus, measurements of CK-MB mass and activity concentrations in plasma with assays based on these specific monoclonal antibodies are comparable for the detection or exclusion of acute myocardial infarction.
Screening for microalbuminuria by use of a rapid, low-cost colorimetric assay.
Authors: Phillipou G , James S K , Seaborn C J , Phillips P J
Published: January 2020

We evaluated the pyrogallol red-molybdate(IV) method for quantification of urinary protein as a screening procedure for microalbuminuria by determining the assay's sensitivity and specificity at different concentrations of urinary albumin as measured by a comparison laser-nephelometric immunoassay. The pyrogallol red-molybdate(IV) method has sensitivity and specificity similar to that for other semiquantitative assays, but it is less expensive and sample throughput can be high if microtiter plate techniques are used.
Rheumatoid factors determined by fluorescence immunoassay: comparison with qualitative and quantitative methods.
Authors: Carpenter A B , Bartkowiak C D
Published: January 2020

Fluorescence immunoassay (FIA), a relatively new technique for measuring rheumatoid factors (RF), is automated, quantitative, and calibrated against the Centers for Disease Control reference material for RF. We studied the FIA method in relation to a panel of RF methods, both qualitative [latex (LA) and sheep cell agglutination (SSCA)], and quantitative [nephelometry and enzyme-linked immunoassay (ELISA)]. Regression analysis revealed a highly significant correlation between FIA and either LA (r = 0.90) or nephelometry (r = 0.87). The correlation between FIA and either SSCA (r = 0.62) or ELISA (r = 0.67) was less strong. FIA had the highest sensitivity (91%) of all these methods; the specificity was 86%. FIA provides an accurate, sensitive, and specific measure of RF, and is a good alternative for laboratories wanting to replace titer methods with automated laboratory analysis.
Erythrocyte sedimentation rate and C-reactive protein compared in the elderly.
Authors: Katz P R , Gutman S I , Richman G , Karuza J , Bartholomew W R , Baum J
Published: January 2020

The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) concentrations were studied in 101 elderly individuals (mean age 72 y) to determine their utility as diagnostic aids in subjects with underlying infection/inflammation. Whereas ESR and CRP were both significantly increased in patients with infection or inflammation, or both, analysis of variance indicated that those subjects still alive six months later had significantly lower ESR values. Analysis of sensitivity, specificity, and positive predictive values indicated that neither test satisfactorily discriminated between patients with and those without ongoing active or chronic disease. Receiver-operating characteristic curve analysis confirmed the low true-positive/false-positive ratios of both ESR and CRP. In the elderly, neither CRP nor ESR has distinct advantages over the other, and both tests evidently have limited utility.
Interference of coumarin therapy with the "Heptest" owing to declining prothrombin concentrations.
Authors: Fischer J , Verbruggen B , Wessels H , Haanen C
Published: January 2020

The Heptest kit (Haemachem, Inc., St. Louis, MO) for quantifying heparin in plasma is based on heparin-mediated inhibition of factor Xa, resulting in prolongation of clotting time. In 19 of 55 plasma samples obtained from 32 patients concurrently receiving coumarin and heparin, Heptest results exceeded true heparin values by more than 0.2 int. unit/mL; four samples showed a deviation exceeding 0.4 int. unit/mL. We show here that these deviations are caused by coumarin-induced decreases of plasma prothrombin. This problem can be circumvented by adding purified prothrombin or normal plasma to the assay mixture.
Characterization of amniotic fluid lamellar bodies by resistive-pulse counting: relationship to measures of fetal lung maturity.
Authors: Dubin S B
Published: January 2020

Resistive-pulse counting studies of amniotic fluid lamellar bodies are presented and demonstrate a strong concordance with the predictions of accepted measures of fetal lung maturity. Uncentrifuged as well as centrifuged specimens could be evaluated, because cells and debris are rejected electronically. The technique is not affected by bilirubin or debris of lysed whole blood, and only mildly by meconium. Lamellar body number density and mean lamellar body volume were determined for 161 uncentrifuged and 241 centrifuged specimens. Number density maturity criteria (40,000/microL and 26,000/microL, respectively) were shown to be highly concordant with established measures of fetal lung maturity; mean lamellar body volume did not extend this concordance. Since electronic cell counters are generally available 24 h per day and the approach requires neither centrifugation nor subjective interpretation and is rapid and inexpensive, it is proposed that determining lamellar body number density by resistive-pulse counting may be a useful initial screen for the assessment of fetal lung maturity.
Allowable limit of error in clinical chemistry quality control.
Authors: Cui Z C
Published: January 2020

Taking the National Clinical Chemistry Quality Control of China National Center for Clinical Laboratory as an example, I present this study of some problems with using the allowable error limit in present-day clinical chemistry quality control, and propose a new allowable error limit for use in external quality control in clinical chemistry.
Interference of common household chemicals in immunoassay methods for drugs of abuse.
Authors: Warner A
Published: January 2020

I report how some adulterants affect results for drugs of abuse in urine as measured by Roche RIA, Syva emit d.a.u., and Abbott TDx fpia (fluorescence polarization immunoassay) for the following drugs: amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, opiates, and phencyclidine (PCP). Sodium chloride interfered negatively with all of these drugs when assayed by emit and caused a slight decrease in measured benzodiazepine concentration by fpia. Drug concentrations were also decreased by added H2O2 (emit: benzodiazepine), Joy detergent (emit: cannabinoid, benzodiazepines, PCP), NaHCO3 (emit: opiate; fpia: PCP), or NaClO [corrected] (emit, RIA, fpia: amphetamines, opiates, PCP; emit, fpia: cannabinoid; emit: benzodiazepines). False-positive results were caused by H2O2 (fpia: benzodiazepines) and Joy (RIA, fpia: benzodiazepine, cannabinoid; fpia: barbiturate, amphetamine). Sodium bicarbonate causes a suspiciously high pH in the urine, NaClO [corrected] an apparently low pH (using pH paper).
Hypomagnesemia and low alkaline phosphatase activity in patients' serum after cardiac surgery.
Authors: Lum G , Marquardt C , Khuri S F
Published: January 2020

Significant decreases in magnesium (Mg) concentration and alkaline phosphatase (ALP, EC 3.1.3.1) activity in serum were seen in patients after cardiac surgery with cardiopulmonary bypass (Group 1), as compared with non-cardiac-surgery patients after general anesthesia (Group 2) or only spinal anesthesia (Group 3). Mean changes for Mg and ALP by the first postoperative day, compared with pre-operative baseline values, were as follows: Group 1: Mg -7.5 mg/L (-38.3%), ALP -46U/L (-48.4%); Group 2: Mg -3.3 mg/L (-17.4%), ALP -17 U/L (-16.5%); and Group 3: Mg -1.9 mg/L (-10.0%), ALP -15 U/L (-14.0%). The decreases in Mg and ALP observed in post-cardiac-surgery patients appear to be a consequence of the cardiac surgery and the cardiopulmonary bypass pump. Measurement of Mg and ALP in a subgroup of 10 cardiac-surgery patients for 10 days postoperatively showed initial decreases, with gradual recovery to near-normal values by the 10th day. That the changes in Mg and ALP seen postoperatively were not attributable to hemodilution alone was confirmed by measuring total-protein concentrations before and after operation. ALP requires Mg ion in vitro for optimal activity, but addition of Mg in the appropriate amounts to sera with low ALP activity did not restore ALP activity. The low ALP activity seen in post-cardiac surgery patients in vivo may perhaps be related to factors other than Mg that were removed by the cardiopulmonary bypass pump.
Proton nuclear magnetic resonance studies of plasma to determine metabolic status of patients with adult respiratory distress syndrome.
Authors: Kuo C D , Wu W G , Wang J H , Chen S M , Chiang B N
Published: January 2020

Adult respiratory distress syndrome (ARDS) is a non-cardiogenic pulmonary edema of various etiologies. Here we report the first application of proton nuclear magnetic resonance (NMR) for the detection of abnormal metabolites in plasma from patients with ARDS. By comparing plasma obtained from the systemic artery with that obtained from the pulmonary artery, we could study the metabolic status of the lung in patients with ARDS. Although their concentrations may vary, the peaks for acetate, acetoacetate, beta-hydroxybutyrate, phenylalanine, and other unidentified compounds in water-suppressed NMR of these patients' plasma were higher than in the normal controls. The proton NMR resonance at a chemical shift of about 7.4 ppm (relative to sodium tetradeutero-3-trimethyl-silylpropionate), presumably caused by phenylalanine and its related metabolites produced by a disordered amino acid metabolism, is detected in greater than 65% of the samples from ARDS patients. We discuss the detection of abnormal metabolites in terms of possible deranged metabolism of carbohydrates, lipids, or amino acids in this syndrome.
Interferographs. Users' Guide to Interferences in Clinical Chemistry Instruments. M. R. Glick and K. W. Ryder. Indianapolis: Science Publishers, Inc., 1987, viii + 190 pp, paperback, $20.00. ISBN 0-930116-07-0
Authors: Young Donald S
Published: January 2020

p 800: In the first column, the correct name (and the address) of the publisher is Science Enterprises, Inc., Box 88443, Indianapolis, IN 46208.

p 1018: Richard Patrick should be added to the list of authors.

p 1110: Corrections to this paper are detailed in a Letter by Hammer, Vol. 35, p 193.

p 1800: Column two, line nine: "12.5" should read "125."

p 1801: Column one, "Linearity" paragraph: "HDL-C" should read "HDL-FC" in lines nine and 14.

p 1803: Column two, last sentence in first full paragraph should read "...automated method, the interferences with the manual method were less."

p 2017: In the legend to Figure 1, the equation for G7 should read: y = -4012 x + 18. In Figure 2, there should be three dots above the 7 glucosyl units coordinate, the third being between the curve and the point just above the curve.

p 2045: In Figure 1 (right), read "41" instead of "91" in the integration values for the 2-3a fraction assay.

p 2141: Right-hand column, line 16: the formula for CNP-NAG should contain two N atoms.

Vol. 35:

p. 17: In the last part of the equation, "0.0835" should read "0.00835", and "0.0759" should read "0.00759."

p 517: See correction note in "The Clinical Chemist."
A regulatory model for clinical laboratories: an empirical evaluation.
Authors: Peddecord K M
Published: January 2020

Clinical laboratories in the United States are subject to various regulatory and accreditation programs, which mandate a broad range of requirements regarding personnel, quality-control systems, and analytical proficiency standards. Reported here, for a cross-section of U.S. laboratories, is the degree of compliance with these regulatory requirements, some other laboratory characteristics, and their relation to analytical proficiency. The results suggest that those laboratory characteristics that predict highest proficiency-test performance differ for each laboratory specialty. Regression models are presented that explain from 12% to 35% of the variation in analytical performance and suggest that factors outside of those specified in the regulatory model and other characteristics measured in this research are important. Indeed, the current regulatory approach may not ensure highest performance. Also discussed are the current status, limitations, and prospects for change of the clinical laboratory regulatory system.
Defective epithelial ion transport in cystic fibrosis.
Authors: Quinton P M
Published: January 2020

In America, cystic fibrosis (CF) is the most common fatal inherited disease. In the past few years new concepts have evolved regarding the etiology of CF, changing from an almost universal acceptance of the abnormality as a disease of abnormal mucus production to that of a disease of abnormal fluid and electrolyte transport. Although mucus production is increased, this probably occurs as a secondary defense or protection against more primary disturbances in electrolyte transport brought on by a defect in Cl- permeability that affects both fluid absorption and fluid secretion. Here I review the progress that has been made and some of the puzzles uncovered in recent investigations of electrolyte transport in secretory and absorptive processes in cystic fibrosis.
Antiarrhythmic drugs and the cardiac sodium channel: current models.
Authors: Sheldon R S , Hill R J , Duff H J
Published: January 2020

The major electrophysiological effect of Class I antiarrhythmic drugs is blockade of the cardiac sodium channel, thereby reducing the initial depolarization of the action potential and slowing impulse propagation. Despite the widespread use of these drugs our understanding of their mechanism of action is incomplete. Models based on electrophysiological studies predict that a receptor for Class I drugs is associated with the sodium channel, and that occupancy of this receptor causes blockade of the sodium channel. Recent radioligand studies with [3H]batrachotoxinin-A benzoate have identified a binding site for Class I drugs associated with rat cardiac myocyte sodium channels, which may be the predicted receptor. Binding of drugs to this site is saturable, reversible, stereospecific, and occurs at pharmacologically relevant concentrations with similar rank order of potency in vivo and in vitro. Drugs appear to bind preferentially to a closed state of the channel, thereby preventing channel opening and subsequent sodium influx.
Current concepts in proteinuria.
Authors: Waller K V , Ward K M , Mahan J D , Wismatt D K
Published: January 2020

Proteinuria, long recognized as a sign of renal disease, is a common laboratory abnormality in children and adults. Proteinuria may be transient or persistent; when persistent, the cause must be determined. Proteinuria may be primarily glomerular or tubular in origin. Glomerular proteinuria is usually an important concern. Tubular proteinuria often indicates the presence of tubulointerstitial or obstructive renal disease. Screening tests are available to detect albumin (the major protein in glomerular proteinuria), but there are no simple tests for immunoglobulin light chains and low-molecular-mass proteins, which predominate in overflow proteinuria and tubular proteinuria. These small proteins can only be detected by more sophisticated assays such as electrophoresis, isoelectric focusing, and chromatography. The association of glomerular and tubular types of proteinuria with specific disorders is reviewed in this paper, and current concepts in laboratory methodology for the study of proteinuria are summarized.
Simultaneous measurement of total and IgA-conjugated alpha 1-microglobulin by a combined immunoenzyme/immunoradiometric assay technique.
Authors: DeMars D D , Katzmann J A , Kimlinger T K , Calore J D , Tracy R P
Published: January 2020

alpha 1-Microglobulin (alpha 1m), a glycoprotein (Mr = 30,000) found in serum and urine, is also present in serum conjugated to monomeric IgA (alpha 1-m-IgA). We have developed a simultaneous enzyme-linked immunoenzyme/immunoradiometric assay that involves three different monoclonal antibodies. Assay of serial dilutions of serum and urine demonstrated parallelism. Normal mean concentrations in serum (n = 75) were: total alpha 1m, 2.33 mumol/L; alpha 1m-IgA, 1.24 mumol/L; unconjugated (free) alpha 1m, 1.09 mumol/L; molar ratio (alpha 1m-IgA/total alpha 1m), 0.53. The mean concentration of alpha 1m in eight urine specimens from normal individuals was 0.19 mumol/L, with no detectable alpha 1m-IgA. A low urinary pH does not significantly affect assay results, unlike assays of beta 2-microglobulin. In patients with myeloma-related renal disease, total and free alpha 1m values for serum correlated well with values for creatinine and beta 2-microglobulin in serum.
Composition of very-low-density lipoproteins in non-insulin-dependent diabetes mellitus.
Authors: Ishibashi S , Yamada N , Shimano H , Takaku F , Akanuma Y , Murase T
Published: January 2020

We studied the characteristics of very-low-density lipoproteins (VLDLs) composition in patients with non-insulin-dependent diabetes mellitus. VLDLs were isolated from 28 diabetics and 33 nondiabetics with a wide range of plasma lipid concentrations, so we could compare VLDL composition between the two groups at similar lipid concentrations. The mean cholesterol and triglyceride concentrations in plasma of diabetic subjects were 2170 (SD 570) and 2510 (SD 2230) mg/L, respectively, and 2230 (SD 560) and 2210 (SD 1830) mg/L in nondiabetics. Diabetic subjects showed positive correlations between plasma triglyceride concentrations and either preprandial blood glucose or glycated hemoglobin values (P less than 0.02 and less than 0.01, respectively). Concentrations of triglycerides, cholesterol, and apolipoproteins (apo) B, CII, CIII, and E in VLDL were not significantly different between diabetics and nondiabetics. At comparable triglyceride concentrations, the chemical compositions of the VLDL in the two groups were still very similar. Dividing the concentration of each component by the VLDL-apo B concentrations yielded similar contents of each component per unit of VLDL for the two groups. We conclude that the composition of VLDLs in diabetics is much the same as that in nondiabetics at comparable concentrations of triglycerides in plasma.