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Biomedical subjects

P Winkel

Publications and source records attributed to P Winkel.

At least 73 records · Page 4Linked to original sources
PubMed1976

Correlation of selected serum constitutents: 2. Consistency of intra-individual correlation values, means, and variances during four months.

We examined whether inter-individual differences in correlation coefficients previously found among subjects truly reflect consistent inter-individual differences or are time-related within an individual. The consitutents studied in this investigation were (a) the enzmes aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase; and (b) the non=protein nitrogen-containing constituents urea, uric acid, and creatinine. Ten healthy women were each subjected to 15 venipunctures over a five-week period (Series I), and, after a two-month interval, were again subjected to 15 venipunctures over a second five-week period (Series II). Before statistical analysis, the data were corrected for the batch-to-batch (day-to-day) arnalytical variation. There was a signiificant (P less than .05) change in the covariance structure (variances or correlation coefficients, or both) between the two series in four of the 10 subjects for the combination of enzymes, and in three other subjects for the combination of nonprotein nitrogen constitutents. Although we found a significant (P lees than .05) average intra-individual variation in the mean values from series to series in the cases of the three enzymes and urea, the magnitude of the inter-series variation in means was relatively small. CV's were: alkaline phosphatase, 3.4%; lactate dehydrogenase, 2.3+; aspartate aminotransferase, 3.3%; urea, 5.0%; uric acid, 1.0%; and creatinine, 1.2%.

Adult↗
PubMed1975

The effects of time of venipuncture on variation of serum constituents. Consideration of within-day and day-to-day changes in a group of healthy young men.

Within-day and the day-to-day variations of serum constituents were evaluated in 11 healthy young men. Eighteen constituents, including electrolytes, metabolites, proteins, and enzymes, were assayed using the AutoChemist MultiChannel Analytic System. Venipunctures were performed at three hours of the day, 8 A.M., 11 A.M., and 2 P.M., on five separate experimental days. A three-factor analysis of variance model was employed to separate analytic variation from biological sources of variation. Statistically significant (p less than .05) group diurnal patterns (main effect of hour) during the six-hour period were found for serum lipids, iron, urea, albumin, total protein, and chloride. A unique individual diurnal pattern (subject-hour interaction) was statistically significant for serum potassium. Statistically significant main effect of month (main effect of day) for the group of subjects was seen for total lipids and potassium; however, the subject-day interaction term, which is an index of the day-to-day variation for the subjects, was significant (p less than .05) for all of the constituents except for sodium ion. The comparison of the variation expected within-day versus the variation seen day-to-day over four months was made by pooling the sources of within-day variation (main effect of hour + subject-hour interaction + subject-day-hour interaction) and by pooling the day-to-day variation terms (main effect of day + subject-month interaction). For serum cholesterol, potassium, acid phosphatase, and phosphate ion, the within-day variation was greater than the day-to-day variation occurring over four months, while the other constituents showed day-to-day variations of a greater magnitude than that experienced during the six-hour period.

Acid Phosphatase↗
PubMed1975

Correlation of selected serum constituents: 1. Inter-individual variation and analytical error.

The intra-subject correlations of three clinically meaningful combinations of serum constituents--(a) potassium, calcium, and albumin; (b) urea, creatinine, and uric acid; and (c) aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase--were studied in 11 healthy men. Duplicate serum samples were obtained at 800 h, 1100 h, and 1400 h on five different days. All assays were performed on the AutoChemist Multichannel Analyzer. Correlation coefficients differed significantly among the subjects for the following six pairs of serum constituents: urea and creatinine, urea and uric acid, creatinine and uric acid, aspartate aminotransferase and lactate dehydrogenase, aspartate aminotransferase and alkaline phosphatase, and lactate dehydrogenase and alkaline phosphatase. Nonbiological positive correlation between analytical errors (i.e., errors of two different assays performed on the same specimen) was demonstrated for two of the pairs: potassium and calcium, and aspartate aminotransferase and lactate dehydrogenase. The error correlations of these two pairs of constituents comprised a significant component of the observed intra-subject correlations. Probable reasons for these analytical error correlations are discussed.

Adult↗
PubMed1975

Diagnostic value of routine liver tests.

In 131 patients on a medical service and 97 patients on a surgical service, in whom a diagnosis of hepatobiliary disease was verified in the hospital, the diagnostic value of routine liver tests performed soon after admission was evaluated by stepwise discriminant analysis. By measurements of alanine aminotransferase, alkaline phosphatases, gamma globulin, prothrombin time, bilirubin, and albumin, half of the medical patients were correctly classified into one of seven diagnostic categories. Aminotransferase contributed most to the classification, being twice as effective as random allocation. Decreasing the number of diagnostic categories to three (hepatitis, fatty liver, and chronic liver disease) increased the frequency of correct allocation to 80%. The allocation of all the patients to seven medical and four surgical diagnostic categories by means of four tests (aminotransferase, alkaline phosphatases, prothrombin time, and bilirubin) was significantly improved by each step with a misclassification rate of 55% when all tests were used. A reduction of the diagnostic groups to five (hepatitis, fatty liver, chronic liver disease, duct obstruction and tumor) increased the frequency of correct allocation to 63%. The analysis demonstrates the limited diagnostic effectiveness of routine liver tests when used alone. The absolute discrimination values depend on the a priori frequencies of the diagnostic groups investigated, and therefore may vary from time to time and from place to place.

Alanine Transaminase↗