bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of lactate dehydrogenase isoenzymes by sodium perchlorate evaluated
Authors: Sanders G T , van der Neut E , van Straalen J P
Published: January 2020

We evaluated a method of measuring lactate dehydrogenase isoenzyme 1 (LD-1) selectively (Clin Chem 1987;33:991-2), in which all other LD isoenzymes were inhibited by adding sodium perchlorate to the reaction medium to a final concentration of 0.825 mol/L. In this study we used the different isoenzymes purified from human autopsy tissue and found that the originally published amount of inhibitor (a) increased the original LD-1 activity and (b) did not eliminate all enzyme activity of LD-2 and LD-3. Interference by LD-2 was further demonstrated. Thus we conclude that this method cannot be used for the selective determination of LD-1 because its results do not accurately reflect the original LD-1 activity.
Effect of occupational lead exposure on lymphocyte enzymes involved in heme biosynthesis
Authors: Rossi E , Costin K A , Garcia-Webb P
Published: January 2020

Lead exposure is a well-known cause of increases in urinary coproporphyrin and erythrocyte zinc-protoporphyrin, so these compounds are often used to monitor occupational lead exposure. The increased concentrations are usually assumed to result from lead inhibition of two of the mitochondrial enzymes of heme biosynthesis, coproporphyrinogen oxidase (EC 1.3.3.3) and ferrochelatase (EC 4.99.1.1). We studied 88 subjects in whom the degree of occupational lead exposure was established by measuring erythrocyte lead and protoporphyrin. Assay of lymphocyte coproporphyrinogen oxidase and ferrochelatase activities showed that these enzymes were unaffected by lead exposure, as was a related enzyme, lymphocyte NADH-ferricyanide reductase. We propose alternative explanations for the increased concentrations of coproporphyrin and zinc-protoporphyrin seen in lead exposure.
Development and evaluation of a simplified dot-blot method for detecting the delta F508 mutation in cystic fibrosis
Authors: Skogerboe K J , West S F , Murillo M D , Tait J F
Published: January 2020

The recent discovery of the cystic fibrosis gene enables DNA-based testing for the direct identification of the deletion of three basepairs coding for phenyalanine at codon 508, the major mutation responsible for the disease. This mutation can be detected by analysis of amplified DNA with allele-specific oligonucleotide probes. We have simplified the procedure of Kerem et al. (Science 1989;245:1073-80) so that the assay can be routinely completed in one working day, starting with an extracted DNA sample. Addition of salmon-sperm DNA to the product of the polymerase chain reaction greatly improved the quality of the hybridization signal. The precision of the method was evaluated by blind analysis and interpretation of results for 100 specimens from 25 patients. The same result was obtained for each patient analyzed separately four times, and four independent observers agreed on the interpretation of results for all 100 specimens. No specimen required repeat analysis to produce interpretable results. We conclude that this method is reliable and convenient for routine clinical laboratory use.
Macro creatine kinase in a case of carnitine palmitoyltransferase deficiency
Authors: Deguchi H , Sugiyama N , Kawamura H , Uemura T , Shimizu A , Yamamoto M
Published: January 2020

A stout man was admitted to the hospital with acute rhabdomyolysis associated with macro creatine kinase (macro-CK, EC 2.7.3.2). This anomaly of CK was detected by gel electrophoresis as an atypical band between CK-MB and CK-MM, classified according to Stein's criteria (Clin Chem 1982; 28:19-24) as type 1, and identified by immunofixation electrophoresis as containing CK isoenzymes MM and MB and immunoglobulin A. Muscle biopsy showed that the etiology of rhabdomyolysis in this case was deficiency of carnitine palmitoyltransferase (CPT, EC 2.3.1.21) in the muscle. We report the first observation of macro-CK in a case of CPT deficiency; its presence may result from recurrent rhabdomyolytic attacks owing to CPT deficiency, and may suggest underlying enzymic abnormality in muscle.
Kinetic measurement of bicarbonate in serum by thiocyanate inhibition of wheat germ phosphoenolpyruvate carboxylase
Authors: Punzalan R R , Johnson G F , Cunningham B A , Feld R D
Published: January 2020

We describe a kinetic enzymic method for serum bicarbonate analysis, using wheat germ phosphoenolpyruvate carboxylase (EC 4.1.1.31) coupled through oxaloacetate reduction with NADH in the presence of malate dehydrogenase (EC 1.1.1.37). Inhibition with potassium thiocyanate yielded first-order kinetics with respect to bicarbonate over the concentration range of 0-45 mmol/L. The inhibitor was chosen by evaluating reaction data in the presence of different anions, with use of a monoexponential model. Criteria for first-order kinetics included a constant reaction half-life over the concentration range and SDest for the model comparable with the magnitude of spectrophotometric noise. We compared our kinetic method (y) with an automated ion-selective electrode method (x), obtaining the regression relationship y = 0.97x + 1.2 mmol/L (r = 0.991; n = 77; mean = 25.5 mmol/L; y = 25.3 mmol/L). Within-run precision from duplicates was 3.1% (mean = 25.2 mmol/L; n = 72). Total analytical precision (n = 12) was 9.4% (mean = 15 mmol/L) for the low control and 4.3% (mean = 32 mmol/L) for the high control. We conclude that the kinetic assay allows use of large serum-to-reagent ratios (1:100) and smaller amounts of NADH than an equilibrium assay. The assay is suitable for automated kinetic analysis.
Assay of functional activity of alpha 1-antichymotrypsin in plasma
Authors: Heidtmann H H , Müller J , Havemann K
Published: January 2020

We introduce a novel assay for measuring active alpha 1-antichymotrypsin (alpha 1X) in human plasma. The assay works on the principle that cathepsin G, immobilized in microtiter plates, preferentially binds alpha 1X, which then can be specifically quantified immunologically. alpha 1X activity can be detected even after 50,000-fold dilution of normal plasma. A linear range was defined for reproducible quantification. There was no interference by alpha 1-proteinase inhibitor or alpha 2-macroglobulin. The assay is designed to detect conditions having decreased alpha 1X activity to further elucidate the biological function of this prominent acute-phase protein.
Polyol concentrations in serum during hemodialysis
Authors: Roboz J , Kappatos D , Holland J F
Published: January 2020

Polyol concentrations were determined by selected-ion monitoring in 10 sample sets taken before dialysis and hourly for 4 h during dialysis. Predialysis concentrations (mumol/L) exceeding the upper limit of normal (mean + 2 SD; n = 33) were found for erythritol (25.4-59.0), threitol (11.5-46.7), and arabinitol (21.0-49.3) in all 10 cases; mannitol (2.7-62.0) in nine cases; and xylitol (0.7-1.3) in eight cases. Concentrations of adonitol, galactitol, and sorbitol were all within normal limits. During dialysis, the concentration of six polyols decreased by approximately 50%, but there were no significant changes for xylitol and adonitol. Erythritol, threitol, and arabinitol concentrations remained more than double the upper limit of normal in all patients after 4 h of dialysis. High residual concentrations were found for mannitol (seven cases) and xylitol (six cases). The results suggest fundamental differences in the homeostasis as well as the dialyzability of different polyols. The potential toxic significance of the high residual concentrations after a 4-h dialysis needs to be investigated.
Insufficient accuracy and specificity of polyanion precipitation methods for quantifying low-density lipoproteins
Authors: Siekmeier R , März W , Gross W
Published: January 2020

Recently, polyanion precipitation assays for low-density lipoprotein (LDL)-cholesterol have been found to underestimate their analyte in normolipidemic samples (Siekmeier et al., Clin Chim Acta 1988;177:221-30). Therefore, accuracy, specificity, and interference by nonesterified fatty acids have been studied for three precipitants (obtained by heparin, dextran sulfate, or polyvinyl sulfate precipitation). At normal concentrations of LDL, precipitation is incomplete, whereas it is nearly quantitative at high concentrations of LDL. The polyvinyl sulfate reagent markedly responds to variations in the amount of non-LDL protein present in the precipitation mixture. In the dextran sulfate and the polyvinyl sulfate method, but not in the heparin method, the percentages of LDL precipitated notably increase as the concentration of the polyanion compound is decreased. In either assay, very-low-density lipoproteins, but not high-density lipoproteins, are significantly coprecipitated (dextran sulfate 28%, polyvinyl sulfate and heparin 66%) in a concentration-independent fashion. Increased concentrations of nonesterified fatty acids markedly interfere with the dextran sulfate and polyvinyl sulfate assay, but do not much affect results with the heparin reagent.
Determination of carrier status in Duchenne and Becker muscular dystrophies by quantitative polymerase chain reaction and allele-specific oligonucleotides
Authors: Prior T W , Papp A C , Snyder P J , Highsmith W E , Friedman K J , Perry T R , Silverman L M , Mendell J R
Published: January 2020

Detection of carriers of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), in the deletion cases, involves calculating gene dosage from Southern blots. We show that the analysis of dosage can also be made from the polymerase chain reaction (PCR) with use of allele-specific oligonucleotides (ASOs). The deletion-prone exons are amplified, transferred to a membrane, and hybridized with ASOs complementary to the exons; the autoradiographic bands are then quantified with a densitometer. After determining the quantitative conditions of the amplification reaction, we were able to identify deletions in a DMD/BMD carrier female. The determination of carrier status via PCR removes several of the technical limitations of Southern analysis and is also cost- and labor-effective.
Monitoring free digoxin instead of total digoxin in patients with congestive heart failure and high concentrations of digoxin-like immunoreactive substances
Authors: Dasgupta A , Saldana S , Heimann P
Published: January 2020

Digoxin-like immunoreactive substances (DLIS) are present in patients with conditions associated with volume expansion (including hypervolemic hypertension, renal failure, and liver failure) and in pre-eclampsia and premature birth. These strongly-protein-bound substances cross-react with anti-digoxin antibodies and cause falsely increased measured concentrations of digoxin in serum. Patients with congestive heart failure (CHF) often have volume expansion and are receiving digoxin therapy. They are also very sensitive to digoxin toxicity and have a very narrow therapeutic range (1.0-1.9 nmol/L). We found monitoring the concentrations of free digoxin (in protein-free ultrafiltrates) helpful in eliminating the interferences of DLIS in CHF patients. DLIS concentrations were measured by fluorescence polarization assay. Concentrations of DLIS were detectable in significantly more (58.3%) of the 12 CHF patients (group A) who were not receiving digoxin than in the 22 normal volunteers tested (13.6%) (P less than 0.05 by both chi-square and Fisher's exact test). Protein-free filtrates from patients or normal volunteers did not show any measurable DLIS activities. We also determined the concentrations of total and free digoxin in 12 patients with CHF who were receiving digoxin (group B) and compared the results with those for 22 patients receiving digoxin without the diagnosis of CHF or any known pathological conditions that could increase DLIS concentrations. The ratio of free to total digoxin in patients in group B was significantly lower (mean = 52.8%, SD 10.2%) than in those receiving digoxin (mean = 72.7%, SD 6.5%) for other reasons (independent two-tailed t-test, P less than 0.05).
Semi-automated colorimetric method for measuring glycohemoglobin, with reduction of nitroblue tetrazolium, evaluated
Authors: Hill R P
Published: January 2020

I evaluated a semi-automated method for measuring glycohemoglobin via reduction of nitroblue tetrazolium by acetone-extracted globin. The simultaneous measurement of glycated protein and total protein with the Roche Mira S analyzer showed good analytical precision (between-batch CV 3.5%-8.5%). Correlation of results (y) with those by a boronate affinity chromatography method (x) gave a regression line of y = 2.0x + 5.9 for samples from patients attending a diabetic outpatient clinic. I also studied reaction kinetics; chloromercuribenzoate concentration, sample volume, and detergent concentration affect the reaction, probably by modulating the reduction of dye by globin-thiol groups.
Variation in concentration of lipids, lipoprotein lipids, and apolipoproteins A-I and B in plasma from healthy women
Authors: Brown S A , Boerwinkle E , Kashanian F K , Swanson N , Patsch W
Published: January 2020

The components of total variation--biological, inter- and intra-individual, and analytical--of plasma lipids, lipoprotein lipids, and apolipoproteins A-I and B have been determined in a population of 44 healthy women, ages 18-35 years. Blood was sampled three separate times at three-month intervals, with no restrictions on diet or physical activity during these periods. The greatest inter-individual variances were observed for high-density lipoprotein (HDL)-cholesterol, HDL2-cholesterol, and total plasma cholesterol. Triglycerides had the highest intra-individual variance (CV 22%). The percentage of inter- and intra-individual variances of apolipoprotein A-I concentrations were more reflective of total HDL- and HDL2-cholesterol content than of HDL3-cholesterol. Concentrations of calculated low-density-lipoprotein cholesterol showed a greater inter-individual variation (18.6%) than did apolipoprotein B (10.7%). The laboratory CVs for these analytes were similar to other reported values. From these data, we computed the expected variation for subjects in our study for single and repeated measurements. Such considerations can influence decision-making in the clinical setting or in designing epidemiological studies.
Development of an enzyme-linked immunosorbent assay with a monoclonal antibody prepared against alpha 1-antitrypsin for diagnostic screening of inflammatory disorders
Authors: Silvestrini B , Guglielmotti A , Saso L , Milanese C , Melanitou E , Grima J , Cheng C Y
Published: January 2020

A monoclonal antibody, designated A2a18b8, of IgG1 class prepared against human alpha 1-antitrypsin, cross-reacts with alpha 1-antitrypsin in the serum of rat and baboon, but not with alpha 1-antitrypsin in serum of rabbit, pig, hamster, guinea pig, dog, or turtle. We used A2a18b8 in an enzyme-linked immunosorbent assay (ELISA) developed for human alpha 1-antitrypsin. Preliminary ELISA screening of 247 serum samples from patients with various inflammatory disorders indicated that the concentration of a specific epitope(s) on alpha 1-antitrypsin recognized by this monoclonal antibody was increased significantly in patients with active systemic lupus erythematosus, mixed connective tissue disease, and rheumatoid arthritis, but not in patients with sclerodermic disorders or Sjögren's syndrome. Evidently, A2a18b8 has diagnostic value in that it selectively recognizes a specific epitope(s) on alpha 1-antitrypsin that is (are) apparently exposed during selective inflammatory disorders.
Effects of analytical method and lyophilized sera on measurements of apolipoproteins A-I and B: an international survey
Authors: Smith S J , Henderson L O , Hannon W H , Cooper G R
Published: January 2020

In 1987 a collaborative study was initiated with 140 laboratories worldwide to evaluate the effects of analytical method and lyophilization on the measurement of different concentrations of apolipoproteins (apo) A-I and B in four lyophilized serum pool samples. This survey confirmed that the lyophilized apo Reference Material of the International Union of Immunological Societies (IUIS) is useful for apo A-I assays as an international serum-based reference material, because among-method variation is negligible. The apo A-I concentration value of 1.24 g/L is now assigned to the IUIS Reference Material (CDC 1883) by a Centers for Disease Control RIA in-house reference method. Use of lyophilized serum preparation as a reference material for some modes of apo B measurement is questionable because of lyophilization and matrix effects. Both radial immunodiffusion and liquid immunoprecipitin methods demonstrated bias in measured apo B concentrations, compared with overall method-weighted means values on the IUIS Reference Material. Because of the uncertainty associated with LDL primary standard, protein analysis, and concentration differences among analytical methods, assigning a single apo B concentration value to the IUIS Reference Material appears inadvisable at present.
Improved kinetic rate assay of urinary N-acetyl-beta-D-glucosaminidase with 2-chloro-4-nitrophenyl-N-acetyl-beta-D-glucosaminide as substrate
Authors: Makise J , Saito E , Obuchi M , Kanayama M , Harakawa K , Yoshida K
Published: January 2020

We have improved the kinetic rate assay method for determining N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30; NAG) activity in urine with use of the synthetic substrate, 2-chloro-4-nitrophenyl-N-acetyl-beta-D-glucosaminide (CNP-NAG), reported previously (Clin Chem 1988;34:2140-2). To increase the solubility of this substrate, we used crown ether (15-crown-5-ether) and ethylene glycol. In addition, we used for the standard solution NAG from human placenta, with specificity corresponding to that of human urine, so that values obtained with the CNP-NAG method and a p-nitrophenyl-NAG method ("MEI Assay NAG") correlated almost completely (r = 0.995, n = 29). Reference values for urinary NAG activity determined by the CNP-NAG method were established for untimed urine specimens from 674 healthy volunteers. The normal reference interval (mean +/- 2 SD) for NAG: 1.6-15.0 (mean 4.9) U per gram of creatinine.
Hyponatremia in patients admitted to a coronary care unit
Authors: Evans J R , McIntosh J P , McIntosh H J , Mitchell P E
Published: January 2020

Calculation of osmolal gap in plasma and urine samples from patients after acute myocardial infarction was carried out to see whether changes in these variables support the concept of a "sick-cell" mechanism being responsible for the hyponatremia associated with acute myocardial infarction. Some supportive evidence was found on the first day after admission but, overall, the evidence was not convincing.
Increased sensitivity in a radioimmunoassay for measuring cyclosporine in lipoprotein fractions
Authors: Brunner L J , Yau J C , Lautersztain J , Luke D R
Published: January 2020

We describe a modification of the commercially available cyclosporine (CAS) 3H-RIA kit, allowing detection of drug in lipoprotein fractions obtained by ultracentrifugation. Sodium bromide solutions containing the lipoprotein fractions were dried and reconstituted with drug-free plasma. Methanolic extractions were centrifuged, and 250 microL of the supernate was dried and reconstituted with 50 microL of methanol. Buffer, radioactive tracer, and monoclonal antibody were then added and incubated for 2 h at 4 degrees C. Samples were subjected to charcoal de-activation and then centrifuged, and the radioactivity in the supernate was counted. The limit of detection of CSA was 2.5 micrograms/L; analytical recovery was between 97.5% and 101.3%. Within- and between-day CVs were less than 9%. We conclude that the present method may be beneficial for therapeutic drug monitoring of CSA in lipoprotein fractions.
Simple enzymatic assay for determining cholesterol concentrations in bile
Authors: Luhman C M , Galloway S T , Beitz D C
Published: January 2020

We use bilirubin oxidase (EC 1.3.3.5) to remove interference by bilirubin in the assay of cholesterol concentration in bile by standard enzymatic methods. Samples are treated for 10 min with nonlimiting amounts of bilirubin oxidase to form biliverdin from bilirubin before the reagent for cholesterol is added. The relatively small interference by biliverdin is easily eliminated by use of sample blanks. The method is simple, convenient, and not hampered by the "chromogen oxidase" activity (the inherent ability of bilirubin oxidase to oxidize some chromogens) that plagues other assays of this type. Using this assay, we have accurately and precisely determined the concentration of cholesterol in bile. Such elimination of bilirubin will also be useful in assays of other biliary constituents or constituents of urine or icteric plasma.
Validation of highly specific and sensitive radioimmunoassays for lutropin, follitropin, and free alpha subunit in unextracted urine
Authors: Landy H , Schneyer A L , Whitcomb R W , Crowley W F
Published: January 2020

Measurement of the urinary excretion of lutropin (LH) and follitropin (FSH) and their common free alpha subunit (FAS) assists in monitoring the maturation of the hypothalamic-pituitary-gonadal axis and in understanding the physiology of the pituitary glycoprotein hormones. Here we describe sensitive, specific polyclonal radioimmunoassays for LH and FSH and a monoclonal radioimmunoassay for FAS for use with urine--assays unperturbed by alterations in urinary pH or osmolarity within the broad physiological range encountered in urine. Concordance between LH, FSH, and FAS concentrations in extracted and unextracted urine samples was high. Linearity and parallelism with the standard curves was observed with addition of 25 to 200 microL of unextracted urine. No effect on glycoprotein concentration was seen after as many as 10 freeze-thaw cycles. The need for extraction was further obviated by the high sensitivity of each assay, reflected by minimum detectable doses well below the concentrations encountered in patients' samples. Thus we have measured gonadotropins in unextracted urine as precisely as in extracted urine. We also have demonstrated an equally versatile assay for urinary alpha subunit, using a monoclonal antibody of high specificity for this monomer in its free, uncombined form. These radioimmunoassays complement assays of gonadotropins and free alpha subunit in serum and will allow longitudinal investigations otherwise limited by the constraints of the patient's blood volume.
Serum angiotensin-converting enzyme in healthy and sarcoidotic children: comparison with the reference interval for adults
Authors: Bénéteau-Burnat B , Baudin B , Morgant G , Baumann F C , Giboudeau J
Published: January 2020

Angiotensin-converting enzyme (ACE) was measured in serum of 187 healthy children between the ages six months and 18 years. Results were pooled for five-year age intervals and compared with the reference values for adults that we previously determined [Clin Chem 1986;32:884-6). Results for each age group were also studied as a function of sex. Children had higher ACE activities in serum than did adults (P less than 0.001), but these activities were age-related only from age four to 18 years. Adolescents showed sex-related differences, with higher serum ACE activities in boys than in girls (P less than 0.05). Both sex- and age-related differences may be related to a steroid hormonal regulation of ACE biosynthesis. We also verified that children with sarcoidosis (n = 20) had significantly increased serum ACE activity. Such physiological variations in serum ACE activity must be taken into account for diagnosing sarcoidosis in children, for following the course of the disease, and for evaluating the accuracy of therapy.
Aminotransferase as a prognostic index in infants with liver disease
Authors: Rosenthal P , Haight M
Published: January 2020

To assess the utility of the serum aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio in a group of infants with liver disorders, we retrospectively analyzed the charts of 73 infants with chronic liver disorders. Patients were considered as having either a good outcome (n = 40) or a poor outcome (n = 33), based upon the clinical course. AST and ALT in serum were measured simultaneously at the time of initial presentation and at various follow-up visits during the first 13 months after birth. At presentation (mean age 1.65 months), there was no difference in the AST/ALT ratios between the good (1.61 +/- 0.62; mean +/- SD) and poor (1.65 +/- 0.78) outcome groups (P = 0.81). However, over time, the AST/ALT ratio increased in patients in the poor-outcome group and decreased in patients in the good-outcome group. Calculating the AST/ALT ratio appears to be an easy, early, and reliable prognostic indicator for infants with hepatic disease, and may be a useful measure for evaluating liver-disease patients.
Method comparison for calcium determination by flame atomic absorption spectrophotometry in the presence of phosphate
Authors: Welch M W , Hamar D W , Fettman M J
Published: January 2020

We investigated the suppressive effects of phosphate on calcium determinations with lanthanum-air/acetylene and potassium-nitrous oxide/acetylene methods, and we evaluated the ability of these methods to meet the suggested analytical goals for urine samples. The 20 g/L La-air/acetylene method was the most nearly accurate for predicting the actual calcium concentrations (t-test value = -0.042), followed by the 2 g/L K-nitrous oxide/acetylene method (t-test value = 0.450), 10 g/L La-air/acetylene (t-test value = -0.733), and finally 5 g/L La-air/acetylene (t-test value = -2.446). The dilution used significantly influences the apparent calcium concentration measured with the La-air/acetylene methods.
A comparison of results for cholesterol in human serum obtained by the Reference Method and by the Definitive Method of the National Reference System for cholesterol
Authors: Ellerbe P , Myers G L , Cooper G R , Hertz H S , Sniegoski L T , Welch M J , White E
Published: January 2020

Here we compare the Reference Method (I) and the Definitive Method (II) for measurement of cholesterol in serum. For pure cholesterol solutions, values by I agree with values by II, but for fresh, frozen, or lyophilized sera, values by I average 1.6% higher than values by II. We conclude that an undetected interference is associated with I. However, the observed difference does not diminish the usefulness of I as an accuracy base for cholesterol measurements, because it is clinically insignificant at present.
Monoclonal immunoradiometric assay of calcitonin improves investigation of familial medullary thyroid carcinoma
Authors: Perdrisot R , Bigorgne J C , Guilloteau D , Jallet P
Published: January 2020

Calcitonin (CT) assay is essential for recognizing medullary thyroid carcinoma (MTC), particularly occult familial MTC. In previous radioimmunoassays of calcitonin, polyclonal antibodies were used. Here we evaluate a new two-site immunoradiometric assay (IRMA) of calcitonin based on use of monoclonal antibodies. We assayed samples from healthy subjects, patients with renal failure, and subjects from families affected by MTC. Basal values for healthy subjects were all less than 10 ng/L. Renal failure is associated with increased basal CT. The CT peak under pentagastrin stimulation in healthy patients was less than 30 ng/L. In familial screening, basal values greater than 10 ng/L or peak values greater than 30 ng/L correspond to subjects with histologically confirmed MCT or micro-MCT. Polyclonal RIA performed in the same subjects failed to detect the moderate increase of CT that IRMA demonstrated. Preliminary results indicate that this new method may allow earlier detection of CT increase and thus improved diagnosis of MCT, particularly in familial screening. Monitoring surgical patients could also be improved by this new assay.
Valproic acid-associated pancreatitis: report of three cases and a brief review
Authors: Lott J A , Bond L W , Bobo R C , McClung H J , Murray R D
Published: January 2020

We describe three patients with seizure disorders in whom pancreatitis or pancreatic injury was probably caused by valproic acid, a widely used anticonvulsant drug. Trivial or no increases of serum amylase (EC 3.2.1.1) but striking increases of serum lipase (EC 3.1.1.3) were common to all patients, as assayed in the Kodak Ektachem. In vitro, valproic acid does not cause any change in serum lipase. In patients with symptoms suggestive of pancreatitis and abnormal values for amylase and (or) lipase, treatment with valproic acid should be discontinued.
Neutral ionophore-based selective electrode for assaying the activity of magnesium in undiluted blood serum
Authors: Rouilly M , Rusterholz B , Spichiger U E , Simon W
Published: January 2020

The concentration of free, ionized magnesium in undiluted blood serum can be determined potentiometrically with a new magnesium-selective carrier in polymeric membrane electrodes (by weight 66% plasticizer, approximately 33% polyvinyl chloride and approximately 1% ionophore). However, discrimination of calcium by the new ionophore-added membrane is not sufficient to keep calcium interference to less than 1%. To correct for the interference by calcium, we determine the calcium activity of the serum sample with a calcium-selective electrode and calibrate the magnesium-selective electrode with standard solutions containing calcium in the concentrations found. In this way we determined the free ionized magnesium in five plasma samples from five different persons and found it to be within the range expected for magnesium in undiluted serum.
Concentrations of free thyroxin and free triiodothyronine in serum of patients with thyroxin- and triiodothyronine-binding autoantibodies
Authors: John R , Henley R , Shankland D
Published: January 2020

Between 1982 and 1989 we identified 47 subjects with spuriously increased concentrations of free thyroxin (FT4) or free triiodothyronine (FT3) related to autoantibody interference in analog FT4 and (or) FT3 methods. The incidence of autoantibody interference observed during one year (1988) was 1 in 2460. In the subjects identified, 51% and 11%, respectively, showed an increased binding of radiolabeled T4 or T3 analog alone; 38% had an increased binding of both. Of 36 patients tested, 71% had autoantibodies to thyroglobulin and microsomal fraction of the thyroid, 19% to microsomal fraction alone, and 9.5% to thyroglobulin alone. In eight subjects, spuriously increased FT4 concentrations were reported with the following FT4 methods (in decreasing order of interference): Coat-A-Count, Amerlex-M, Amerlite, Seria, Magic Lite, Amerlex-MAB. In the same eight subjects, Amerlex-M and Seria reported spuriously increased concentrations of FT3.
Medically significant concentrations of prostate-specific antigen in serum assessed
Authors: Bernstein L H , Rudolph R A , Pinto M M , Viner N , Zuckerman H
Published: January 2020

We used the method of Rudolph et al. (Clin Chem 1988; 34:2031-8) to find information in the data from correlated determinations of acid phosphatase (PAP, EC 3.1.3.2; DuPont aca) and prostate-specific antigen (PSA, Hybritech). We described there how we assign medical decision limits for two or more correlated variables and convert the database to a binary coded message, allowing separation of a selected disease class with minimum error. The decision point, analogous to a percentile upper limit on the ordered values of each variable in the reference group, satisfies the maximum entropy constraints of reference, producing a minimum entropy for the binary coded patient database. We found maximum entropy decision points at PAP = 0.75 U/L and PSA = 22.8 micrograms/L. Patients with PSA values exceeding 22.8 micrograms/L had no benign prostatic disease except for five patients with benign prostate hyperplasia (BPH) with adjacent colon carcinoma (95.3), BPH with infarction (27.6), BPH (23.4) 28.1), or acute prostatitis (34.6). We consider PSA exceeding 22.8 micrograms/L as indicative of carcinoma of the prostate, stage C or D, in the absence of disconfirming evidence. Another decision value for PSA is 11.3 micrograms/L. This bounds the region between 11.3 and 22.8 micrograms/L, where the frequency of BPH is 1.5 times that for adenocarcinoma. At PSA less than 11.3 micrograms/L there is a high frequency of BPH. PSA concentration is not correlated with prostatic size (mass) or with prostatitis. A metastatic carcinoma is as likely to be nonprostatic as prostatic when the PSA concentration is less than 11.3 micrograms/L.
Effect of serum lyophilization on the rate constants of enzymatic methods for measuring cholesterol
Authors: Kroll M H , Chesler R
Published: January 2020

We determined the equilibrium absorbances and rate constants for two enzymatic methods, aca (DuPont) and RA-1000 (Technicon), used in determining cholesterol in reconstituted lyophilized serum. The lyophilized materials included two serum pools, three control materials, a College of American Pathologists' survey material, and Standard Reference Material no. 909. We calibrated the reagents with aca standards for cholesterol (DuPont). The difference in the mean concentrations of cholesterol (aca - RA-1000) was -0.09 g/L overall and was not statistically significant by analysis of variance. The mean rate constant for all materials was 0.23 min-1 for the aca and 1.42 min-1 for the RA-1000, significantly different (P less than 0.001). Lyophilization causes lower results for the aca method than for the Ra-1000, because the reaction rate for the aca method is slower and has not reached equilibrium when the final absorbance reading is made.
Adjusted ionized calcium (at pH 7.4) and actual ionized calcium (at actual pH) in capillary blood compared for clinical evaluation of patients with disorders of calcium metabolism
Authors: Thode J , Holmegaard S N , Transbøl I , Fogh-Andersen N , Siggaard-Andersen O
Published: January 2020

We report results for adjusted ionized calcium (at pH 7.4) and actual ionized calcium (at actual pH) in capillary blood from 183 patients with disorders of calcium metabolism (primary hyperparathyroidism, secondary hyperparathyroidism of malabsorption, primary hypoparathyroidism, Paget's disease, acromegaly, hypercalcemia of malignancy, osteoporosis, sarcoidosis, idiopathic hypercalciuria, and familial hypocalciuric hypercalcemia). The correlation and the equation for the linear regression between adjusted ionized calcium (y) and actual ionized calcium (x) were y = 1.011x + 0.005 mmol/L, r = 0.992, Sy,x = 0.021 mmol/L. Results were similar within each diagnostic group. Consistent agreement between adjusted and ionized calcium was observed in 96.7% of patients representing a variety of the most frequently encountered disorders of calcium metabolism. Thus we find adjusted ionized calcium to be as useful as actual ionized calcium for evaluation of patients with such disorders. Adjusted ionized calcium may therefore also be a logical choice for establishing agreement between laboratories for reference intervals in healthy adults.
A two-tube immunochemical method for determination of CK-MB isoenzyme in serum evaluated
Authors: Panteghini M , Bonora R , Pagani F
Published: January 2020

A new commercial kit (Impres-MB; International Immunoassay Labs.) recently was introduced for measuring the MB isoenzyme of creatine kinase (CK-MB) based on the use of monoclonal antibodies. After antibodies to CK-MM isoenzyme are added to precipitate the CK-MM, antibodies to CK-M monomer are added to precipitate the M-subunit isoenzymes of CK. Subtracting the enzymatic activity of the second supernate from the residual activity in the first yields the activity of CK-MB. Results are not affected by CK-BB, mitochondrial CK, or adenylate kinase. However, the anti-CK-MM antibodies precipitated only about 98% of serum CK-MM and may have partly precipitated CK-MB isoenzyme (average analytical recovery of CK-MB, 86.6%). Comparison between Impres-MB (y) and electrophoresis (x) yielded the following linear-regression equation: y = 0.79x + 3 (r = 0.982, n = 97). Data for CK-MB temporal kinetics, obtained from patients with myocardial infarction, correlated significantly in both methods; however, peak activity values of CK-MB were significantly different, confirming that the difference between the new method and the electrophoretic method average 20%.
A study of the CEDIA digoxin immunoassay
Authors: Murthy V V , Karmen A
Published: January 2020

We evaluated the CEDIA digoxin immunoassay (Microgenics, Inc., Concord, CA), as performed with the Cobas-Bio centrifugal analyzer. In assays of sera with known concentrations of digoxin, the enzyme activity, measured when two beta-galactosidase (EC 3.2.1.23) fragments were combined according to the assay format, was proportional to the digoxin concentration. Results of assays of sera containing 0 to 3 micrograms of digoxin per liter correlated well when compared with an RIA method: CEDIA, microgram/L = 1.00 x RIA - 0.06 microgram/L (n = 90, r = 0.95, Sxy = 0.05). Duplicate assays of three control sera containing 0.8, 2.2, or 3.3 micrograms/L, each analyzed 20 times a day with each group of patients' samples, gave within-run CVs of 1-3% and day-to-day CVs of 3-12%. The reconstituted CEDIA reagents were stable for at least a month at 5 degrees C. As many as 25 samples and controls can be assayed in half the time needed to complete a similar number of RIA measurements with comparable results.
Role of the clinical laboratory in guiding treatment of Amanita virosa mushroom poisoning: report of two cases
Authors: Piering W F , Bratanow N
Published: January 2020

Historically, mortality after Amanita mushroom ingestion has ranged from 50% to 90%. Prompt diagnosis is imperative, and aggressive therapeutic measures must be instituted quickly to improve the outcome. We report successful treatment of two cases of A. virosa poisoning by use of combined therapies, including thioctic acid and hemoperfusion.
S-100ao protein in serum during acute myocardial infarction
Authors: Usui A , Kato K , Sasa H , Minaguchi K , Abe T , Murase M , Tanaka M , Takeuchi E
Published: January 2020

Concentrations in serum of S100ao protein (alpha alpha form of S-100 protein, which is present at high concentrations in heart muscle) were successively measured by enzyme immunoassay in 21 patients with acute myocardial infarction (AMI) and six with angina pectoris (ANP). Results were compared with measurements of creatine kinase isoenzyme MB (CK-MB) concentrations in the same specimens. Mean S100ao concentrations in sera from 100 healthy adults were 0.12 (SD 0.08) microgram/L. In patients with AMI, S100ao concentrations were 4.74 +/- 5.27 micrograms/L at admission, peaked 8 h after admission (23.5 +/- 27.7 micrograms/L), then decreased gradually. Among nine AMI patients who were admitted within an hour after their attack, eight showed abnormally high concentrations of S100ao in serum (greater than 0.5 microgram/L), whereas only four showed abnormally high CK-MB concentrations (greater than 5 micrograms/L) in sera at the time of admission. Serum S100ao concentrations remained within the normal range in all six patients with ANP; however, serum CK-MB concentrations were increased in two of them. Therefore, serum S100ao is useful not only for detection of AMI but also for differentiating AMI from ANP.
Direct and indirect techniques for free thyroxin compared in patients with nonthyroidal illness. III. Analysis of interference variables by stepwise regression
Authors: Csako G , Zweig M H , Ruddel M , Glickman J , Kestner J
Published: January 2020

We applied stepwise regression for multivariate analysis of data for free thyroxin (FT4) in serum and for other laboratory tests of thyroid function in patients with nonthyroidal illness. Using the maximum R2 improvement and backward elimination methods to test five variables [prealbumin, albumin, T4-binding globulin (TBG), free fatty acids (FFA), and FFA/albumin molar ratio], we found that the variables with the greatest predictive power clustered according to the methodology of FT4 measurement. Thus, we best predicted the FT4 results obtained by 16 techniques as follows: FT4 measured by one-step (analog) RIAs, with albumin; FT4 determined by two-step (sequential) RIAs, with FFA or FFA/albumin molar ratio; FT4 estimated by a binding-rate-based RIA or conceptually related FT4 indices [based on triiodothyronine (T3) uptake], with TBG; FT4 measured by equilibrium dialysis, with TBG and FFA/albumin molar ratio; and T4/TBG ratios, with either none or prealbumin and albumin. We could very highly (P less than 0.001) predict total T4 and T3 by considering TBG, and total T3 also by considering prealbumin and albumin, whereas reverse T3 was predictable with prealbumin only (negative relationship). We found comparatively weak associations between thyrotropin (TSH) and albumin or TBG. In clinical practice, abnormalities in key variables should call attention to possible effects of these variables on FT4 and other thyroid-test results and thus to the need for appropriate correction or alternative testing.
Human choriogonadotropin (hCG): comparisons between determinations of intact hCG, free hCG beta-subunit, and "total" hCG + beta in serum during the first half of high-risk pregnancy
Authors: Thomas C M , Reijnders F J , Segers M F , Doesburg W H , Rolland R
Published: January 2020

We have studied the concentrations of intact human choriogonadotropin (hCG) and the free hCG beta-subunit in blood samples from singleton pregnancies at risk for habitual or threatened abortion. The samples were obtained weekly between the 6th and 12th weeks and in the 14th and 16th weeks of gestational age. The concentrations of intact hCG, of the free hCG beta-subunit, and of "total" hCG (i.e., intact hCG and the free hCG beta-subunit: hCG + beta) were measured in serum by specific immunoassays. The distributional statistics (the 5th, 50th, and 95th percentiles) of "total" hCG + beta and of intact hCG showed very similar patterns, whereas the response curves for the free hCG beta-subunit showed very much lower serum concentrations. From these data we also estimated distributional statistics of the percent molar ratios of free hCG beta-subunit to intact hCG. We conclude that (a) the relatively small proportion of free hCG beta-subunit in serum during the first half of singleton pregnancy is far too low to interfere with the applied "total" hCG assay, as compared with the serum values obtained for intact hCG, and (b) the percent molar ratios of free hCG beta-subunit to intact hCG, or to "total" hCG + beta, never exceeded 1.0% throughout the period of pregnancy studied.
A validation study of selected methods routinely used for measurement of cyclosporine
Authors: Blick K E , Melouk S H , Fry H D , Gillum R L
Published: January 2020

We compare four methods for measuring cyclosporine (CyA) in plasma and whole blood of transplant patients: HPLC, RIA with a polyclonal antibody, RIA with a monoclonal antibody, and fluorescence polarization immunoassay (FPIA). The monoclonal RIA procedure correlated acceptably with HPLC, with slope = 1.21, r = 0.97, and Sy,x = +/- 40.1. However, the FPIA, done in three separate instruments, correlated relatively poorly with HPLC, giving slopes of 1.67, 1.51, and 2.32; correlation coefficients of 0.72, 0.43, and 0.83; and Sy,x = +/- 205.4, +/- 334.5, and +/- 222.4. The polyclonal RIA correlated reasonably well with HPLC, with a slope = 1.15, r = 0.90, and Sy,x = +/- 72.6. Values for individual patients with increases both in gamma-glutamyltransferase and creatinine showed very poor correlation between FPIA and HPLC, which suggests that metabolite cross-reactivity with FPIA is significant and unpredictable in patients with liver dysfunction coexisting with renal dysfunction. Evidently, the monoclonal RIA can be substituted for HPLC, if the therapeutic range is adjusted for the 21% higher results obtained by RIA.
Diagnosis of the multiglandular endocrine neoplasias
Authors: Bone H G
Published: January 2020

Multiglandular endocrine neoplasia syndromes are disorders characterized by autosomal dominant inheritance patterns and by the striking patterns of clinical presentation of these endocrine tumors, which are often hormonally active. Not every patient with adenomas of more than one endocrine gland has one of these classical familial syndromes. This paper will deal with the specific diseases known as multiglandular endocrine neoplasia Types 1, 2A, and 2B. Types 2A and 2B are also known as Types II and III.
Chemiluminescent measurement of total urinary nitrogen for accurate calculation of nitrogen balance
Authors: Skogerboe K J , Labbé R F , Rettmer R L , Sundquist J P , Gargett A M
Published: January 2020

This instrumental method for total urinary nitrogen (TUN) is based on the principle of gas-phase chemiluminescence. Results correlate well with measurements of TUN by the Kjeldahl method, which has long provided the means to calculate nitrogen balances for nutritional management. In recent years, because of speed and convenience of measurement, determination of urinary urea nitrogen (UUN) has been substituted for Kjeldahl TUN. However, in patients requiring aggressive nutritional support, the UUN may not be a valid indicator of total nitrogen excretion. We compared nitrogen balances calculated for patients, using both UUN and chemiluminescence TUN data. For both normal and hospitalized populations, nitrogen balance calculated from UUN data exceeded that calculated from TUN data. We show that use of UUN data in calculating nitrogen balance may result in an incorrect assessment of many patients as being in positive nitrogen balance. TUN determined by chemiluminescence evidently provides a simple means of calculating nitrogen balance more nearly accurately.
Indicators of acute renal-transplant rejection in patients treated with cyclosporine
Authors: Mueller P W , Delaney V , MacNeil M L , Caudill S P , Steinberg K K
Published: January 2020

We evaluated the ability of three enzymes--N-acetyl-beta-D-glucosaminidase (NAG; EC 3.2.1.30), alanine aminopeptidase (AAP; microsomal aminopeptidase, EC 3.4.11.2), and gamma-glutamyltransferase (GGT; EC 2.3.2.2)--and adenosine deaminase binding protein (ABP) in urine to predict or confirm renal-transplant rejection in patients treated with cyclosporine. We measured the enzymes daily during the early post-transplant hospital stay of 104 renal-transplant recipients (72 men and 32 women). We also measured ABP in 32 of these patients. We analyzed the data by calculating the activity ratio of each day's test value to the previous day's result and optimized the sensitivity (SN) and specificity (SP) to determine the optimal ratio for each test. The results indicate that cyclosporine treatment reduces the optimal sensitivity and specificity of these tests. Three comparable tests (ABP, GGT, and AAP) yield the best optimal values (SN = 0.77, 0.69, 0.77; and SP = 0.71, 0.74, 0.63, respectively), and the NAG test yields the lowest combination of sensitivity and specificity (SN = 0.62, SP = 0.66). All four tests were less sensitive and specific than the plasma creatinine test (optimal day-to-day difference = 5 mg/L). However, the ABP and AAP tests gave indications of rejection at least 24 h before clinical diagnosis for 50% of the patients experiencing rejection, while early plasma creatinine increases of 5 mg/L occurred in only 19% of this group.