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Biomedical subjects

W Gerhardt

Publications and source records attributed to W Gerhardt.

At least 19 recordsLinked to original sources
PubMed1992

The prognostic value of serum troponin T in unstable angina.

BACKGROUND: Cardiac troponin T is a regulatory contractile protein not normally found in blood. Its detection in the circulation has been shown to be a sensitive and specific marker for myocardial cell damage. We used a newly developed enzyme immunoassay for troponin T to determine whether its presence in the serum of patients with unstable angina was a prognostic indicator. METHODS: We screened 109 patients with unstable angina (25 with accelerated or subacute angina and 84 with acute angina at rest) for serum creatine kinase activity, creatine kinase isoenzyme MB activity, and troponin T every eight hours for two days after admission to the hospital. The outcomes of interest during the hospitalization were death and myocardial infarction. RESULTS: Troponin T was detected (range, 0.20 to 3.64 micrograms per liter; mean, 0.78; median, 0.50) in the serum of 33 of the 84 patients (39 percent) with acute angina at rest. Only three of these patients had elevated creatine kinase MB activity (two were positive for troponin T, and one was negative). Of the 33 patients who were positive for troponin T, 10 (30 percent) had myocardial infarction (3 after coronary-artery bypass surgery), and 5 of these died during hospitalization. In contrast, only 1 of the 51 patients with angina at rest who were negative for troponin T had an acute myocardial infarction (P less than 0.001), and this patient died (P = 0.03). Thus, 10 of the 11 patients with myocardial infarctions had detectable levels of troponin T; only 1 had elevated creatine kinase MB activity. Troponin T was not detected in any of the 25 patients with accelerated or subacute angina, and none of these patients died. CONCLUSIONS: Cardiac troponin T in serum appears to be a more sensitive indicator of myocardial-cell injury than serum creatine kinase MB activity, and its detection in the circulation may be a useful prognostic indicator in patients with unstable angina.

Aged↗
PubMed1991

S-troponin T in suspected ischemic myocardial injury compared with mass and catalytic concentrations of S-creatine kinase isoenzyme MB.

In a multicenter study we compared three tests for ischemic myocardial injury (IMI): a new, automated enzyme immunoassay for S-troponin T (S-TNT; Boehringer Mannheim) and two S-creatine kinase (CK) isoenzyme MB assays (mass and catalytic concentrations). For critical evaluation of clinical sensitivity, we studied 243 cases with an IMI prevalence of 43% and an 18% prevalence of cases with unstable angina. Relative peak values of S-TNT and S-CK-MB (mass) after onset of pain were four- to fivefold higher than S-CK-MB (catalytic) results. Increases of S-TNT and S-CK-MB (mass), even though still within their reference ranges, indicated minor myocardial damage in about one-third of the cases primarily classified as unstable angina. The diagnostic window for S-TNT ranged from hours to weeks after the acute episode. The time courses were frequently biphasic, with the initial S-TNT peak closely paralleling that of the mass concentrations of S-CK-MB. With a biological half-life for S-TNT of 2 h, the prolonged increases in S-TNT indicate a continuous release of S-TNT from necrotizing cells. Clinical specificities of S-TNT and S-CK-MB (mass) were greater than that of S-CK-MB (catalytic), even in the presence of 30% to 40% severe skeletal muscle injuries. The combination of S-TNT and S-CK-MB (mass) is excellent for detection of acute IMI, including minor myocardial damage.

Catalysis↗
PubMed1990

Evaluation of test sensitivity and test specificity of three field methods for quantification of chloroquine in urine using liquid chromatography as reference method.

We have evaluated three quantitative colorimetric methods [bromthymol blue (BTB), Haskins, and Saker-Salomons (S-S)] for measurement of concentrations of chloroquine (CQ) in urine. A graphical evaluation of test sensitivity and test specificity at different concentrations of CQ in authentic urine samples was used. Liquid chromatography (LC) was used as a reference method. The Haskins method showed the highest test specificity (89%) and test sensitivity (97%), at a discrimination value of 2 mumols/L. At the same sensitivity (97%) as the Haskins method, S-S and BTB methods had test specificities of 49 and 13%, respectively. The correlation coefficients between the LC method and the colorimetric methods were all higher than 0.94 at a urinary concentration range of 2-100 mumols/L. The intra- and interassay variations for the colorimetric methods were all uniformly less than 15% at 2 mumols/L, but the Haskins method showed less variation than the other two methods.

Child↗
PubMed1989

[Enzyme diagnosis of acute myocardial infarction].

During the past decade, determinations of enzyme concentrations in the blood in patients admitted with suspected acute myocardial infarction has been of increasing significance not only for early elucidation but also for establishing the correct diagnosis. This is partly the result of methods which can demonstrate the presence of myocardium-related isoenzymes and also because of the physiological basis for the release of enzymes and their metabolism bas been elucidated. In the present report, guidelines for clinical employment of enzyme investigations in acute myocardial infarction are presented. By means of blood sampling twice or thrice within a time interval af approximately 8-24 hours after the presumed time of infarction and determination of a limited number of enzymes in these samples, it is possible to exclude or confirm the presence of an infarct with high probability.

Humans↗
PubMed1988

[The metabolism of various acaloric compounds with fatlike properties in rats].

Pseudofats as total substituted long-chain esters and ethers of polyhydroxyl compounds (sucrose, triglycerol, and polyethyleneglycol) are more or less indifferent against gastrointestinal enzymes, but display specific metabolic effects on lipid metabolism especially on cholesterol synthesis in liver, plasma lipid level, and fecal cholesterol excretion. Among the different tested compounds there exist similarities as well as differences, which are to consider as an indication for a specific relationship between structure and effect. These relations are more closely investigated and critically discussed.

Animals↗
PubMed1988

Graphical analysis of laboratory data in the differential diagnosis of cholestasis: a computer-assisted prospective study.

Data on 15 laboratory analytes obtained in 145 prospectively investigated cholestatic patients with viral hepatitis, chronic intrahepatic cholestasis and extrahepatic biliary obstruction were submitted to a computer-based graphical evaluation using probabilistic test analysis. This revealed a marginal utility for alkaline phosphatase, gamma-glutamyltransferase and the direct/total bilirubin ratio at specific cut-off points for the exclusion of extrahepatic cholestasis (PVneg 90%-100%). Aspartate aminotransferase and alanine aminotransferase values with cut-off points at 200 U/l and 300 U/l, respectively, were powerful discriminators between acute viral hepatitis and the other disease categories, while lactate dehydrogenase, erythrocyte sedimentation rate and the ratios gamma-glutamyltransferase/alanine aminotransferase as well as total bilirubin/gamma-glutamyltransferase were useful at specific cut-off points indicating the absence of this diagnosis (PVneg 92%-100%). An aspartate aminotransferase/alanine aminotransferase ratio above 1.5 and serum gamma-globulin concentrations above 20 g/l strongly suggested cholestasis due to chronic parenchymal liver disease (PVpos 92% and 90%, respectively). This graphical approach to laboratory data analysis enhances the understanding of the interrelations between cut-off points and sensitivity, specificity and predictive values and also of the influence of disease prevalence on disease prediction. It also adds to present knowledge by demonstrating the clinical relevance of several readily available, albeit rarely utilized diagnostic analytes.

Blood Chemical Analysis↗
PubMed1988

Multicenter evaluation of a specific pancreatic isoamylase assay based on a double monoclonal-antibody technique.

Eleven evaluators from nine laboratories in five countries evaluated a new immunoinhibition method for pancreatic isoamylase determination that is as simple to perform as that for total amylase. The precision at low and intermediate activity concentrations was superior, and at high concentrations it equalled that of the wheat-germ inhibitor method. The test was linear to approximately 2000 U/L, depending on the instrumentation used. The percentage salivary isoamylase activities remaining in specimens after reaction with two monoclonal antibodies ranged from 2 to 4.4%. Comparative studies showed good correlation with the wheat-germ inhibitor (r greater than 0.978) and electrophoresis methods (r = 0.920). Hemolysis, lipemia, and bilirubinemia have no effect on results. Interlaboratory studies demonstrated excellent transferability of the method, if instruments are calibrated with the same calibrator. Reference intervals for pancreatic isoamylase are 13 to 64 U/L (25 degrees C), 13 to 83 U/L (30 degrees C), and 17 to 115 U/L (37 degrees C). A clinical evaluation of patients with acute pancreatitis showed that pancreatic isoamylase has a greater clinical sensitivity than total amylase.

Acute Disease↗
PubMed1986

SCE Nordic alpha-amylase study. II: Assessment of proposed calibration procedure. A report by the Scandinavian Committee on Enzymes (SCE).

Eighty-seven Nordic Hospital laboratories participated in a joint SCE-NORDKEM follow-up study of the long-term stability of the previously established calibration factors for a number of alpha-amylase routine methods based on six different substrates. Human control materials with 90% pancreatic, 90% salivary, and pure pancreatic alpha-amylases were measured by the participants. The data were plotted before and after calibration of each method using a human pancreatic calibrator with an assigned catalytic concentration of 390 U/l (Phadebas blue starch method, 37 degrees C). As in the previous study, carried out 9 months earlier, the pre-calibration values varied over a six-fold range. The post-calibration values of all methods except those based on a tetraose substrate showed an acceptable inter-laboratory comparability. As a temporary measure, SCE recommends that the Nordic laboratories calibrate the accepted routine methods by their individual calibration factor. Detailed suggestions for calibration procedures and a discussion of the principles of transferability will shortly be published by the SCE in this journal.

Calibration↗
PubMed1985

SCE Nordic alpha-amylase method selection and calibration study. A report by the Committee of Enzymes of the Scandinavian Society for Clinical Chemistry (SCE).

Seventy-six Nordic routine laboratories participated in a joint SCE-NORDKEM study comprising evaluation, selection, and temporary calibration of amylase methods. Human control materials with known fractions of salivary and pancreatic amylase were determined by seven routine amylase assays based on substrates with glucosyl (G) chain lengths G4, G5, G5-6, G7, G9, amylopectin and blue starch polymer (Phadebas). The data were plotted before and after calibration of each method using a human pancreatic calibrator with an assigned value of 390 U/l (37 degrees C, Phadebas). the study led to three conclusions: The analytical overestimation of salivary to pancreatic amylase ratio (S:P) increased with decreasing number of glucosyl units in the substrates. Relative to the S:P value of blue starch polymer (set at 1.00), for example, tetraose mean S:P value was 1.55. The hydrolysis rates relative to that with blue starch polymer decreased with the number of glucosyl units in the substrates. The precalibration values of all methods spread over an approximately six-fold range. Post-calibration values of all methods, except tetraose, showed an acceptable inter-laboratory comparability. The CV values for low, medium, and high controls were about 5.5, and 6% respectively. As a temporary solution to the current problem of diverse amylase assays, the SCE suggests calibration of the methods considered acceptable in this study. The long-term effects will be evaluated in a follow-up study within a year.

Calibration↗
PubMed1985

Specific immunoassay of alpha-amylase isoenzymes in human serum.

A monoclonal antibody (66C7) was prepared that specifically binds human salivary amylase (EC 3.2.1.1); it cross reacts with human pancreatic amylase by less than 1%. Two procedures are described for determination of isoamylases in human serum with this antibody: an enzyme immunoassay for determining amylase of salivary origin, and a routine method in which this amylase is immunoprecipitated and the remaining (pancreatic) amylase activity is assayed. Results by the two methods correlate well.

Antibodies, Monoclonal↗