Clinical chemistry
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Comparative Study
Variations in amylase isoenzymes and lipase during acute pancreatitis, and in other disorders causing hyperamylasemia.
We compare the clinical value of assay of amylase (EC 3.2.1.1) isoenzymes with that of lipase (EC 3.1.1.3) in serum from patients with proven acute pancreatitis or with hyperamylasemia from other causes. In the former group we measured amylase, lipase, and isoamylases daily. Lipase and P(pancreas)-type isoamylases reached the highest mean values on the first day of an attack of acute pancreatitis (day one). ⋯ In the group of patients with hyperamylasemia from other origins, three had macroamylasemia, one had mumps, one had abdominal trauma without pancreatic injury, and one had pelvic inflammatory disease. The specific pattern of macroamylase on electrophoresis permitted a precise diagnosis of macroamylasemia; normal lipase had only ruled out pancreatitis. In the three other cases, lipase and isoamylases excluded pancreatic involvement.
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We have developed a multi-stage computer algorithm to transform non-normally distributed data to a normal distribution. This transformation is of value for calculation of laboratory reference intervals and for normalization of clinical laboratory variates before applying statistical procedures in which underlying data normality is assumed. The algorithm is able to normalize most laboratory data distributions with either negative or positive coefficients of skewness or kurtosis. ⋯ Powerful statistical tests of data normality in the procedure help the user evaluate both the necessity for and the success of the data transformation. Erroneous assessments of data normality caused by rounded laboratory test values have been minimized by introducing computer-generated random noise into the data values. Reference interval endpoints that were estimated parametrically (mean +/- 2 SD) by using successfully transformed data were found to have a smaller root-mean-squared error than those estimated by the non-parametric percentile technique.
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We describe a fully automated method of analysis for plasma epinephrine and norepinephrine by use of a two-column system of "high-performance" liquid chromatography. Catecholamines in deproteinized plasma are purified on the first (preparation) column, then transferred automatically to the second (analytical) column in which epinephrine and norepinephrine are resolved. These compounds are then determined fluorometrically with a continuous-flow reaction system by the trihydroxyindole method. ⋯ One assay can be completed in 30 min, and greater than 1 mL of plasma is required for the procedure. The within-run CV in the chromatographic determination of pooled plasma was greater than 3%, and the analytical overall recovery of the two compounds was 95%. The concentrations in plasma of medical students at rest were 0.32 (SE 0.06) nmol/L for epinephrine and 0.98 (SE 0.08) nmol/L for norepinephrine.
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In this quantitative method for detection of skeletal alkaline phosphatase (EC 3.1.3.1) activity in human serum, intestinal and placental alkaline phosphatase activities are recognized by their susceptibility to inhibition by L-phenylalanine, and skeletal and hepatic alkaline phosphatases are distinguished by their different sensitivities to inactivation by heat. Alkaline phosphatase isoenzymes prepared from organ sources may behave differently from the corresponding isoenzymes in serum. Our procedure allows us to include organ-derived internal standards of skeletal, intestinal, and biliary alkaline phosphatase to minimize between-assay variation. In preliminary applications, we have found that (a) total serum alkaline phosphatase activity is extremely variable in post-menopausal osteoporotic subjects and is not a reliable index of skeletal alkaline phosphatase activity; (b) seven osteoporotic patients responding to therapy with sodium fluoride with increased bone formation showed increased skeletal alkaline phosphatase activity in their serum as compared with age-matched controls (p less than 0.005); and (c) 10 post-menopausal osteoporotic patients responding to therapy with stanozolol with increased total body calcium showed an increase in circulating skeletal alkaline phosphatase activity (p less than 0.001).
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Comparative Study
Determination of hemoglobin derivatives with IL 282 CO-oximeter as compared with a manual spectrophotometric five-wavelength method.
Hemoglobin derivatives as determined with the IL 282 CO-Oximeter correlated well with results by a manual five-wavelength method, which in turn had been checked against established methods for one or two derivatives. Measurement of total hemoglobin yielded almost identical results with both methods. ⋯ Although the IL 282 CO-Oximeter has not been constructed for the determination of sulfhemoglobin, it appeared that the instrument can still give a strong indication as to the presence of this hemoglobin derivative. Results from the IL 282 for fetal human blood should be used with caution, especially because of the possibility of falsely high HbCO readings.