[Base activity of glycogen phosphorylase b in human serum. Study of reference and discrimination values]

Serum glycogen phosphorylase activity as one of the sensitive indicators for the diagnosis of acute heart infarction was determined at 216 healthy probands using a standardized fluorometric procedure with a detection range from 0.03 to 6 nmol/s x l serum. Basal activity was averaged at 1.22 +/- 0.39 nmol/s x l serum with a confidence interval of C.I.95 1.168 ... 1.272. Due to the estimated Gaussian distribution of the individual activity values (n = 216) the reference range was calculated from 0.5 to 2.0 nkat/l (2.5- to 97.5-percentile, respectively), the latter one being equal to the reference value of the glycogen phosphorylase activity in healthy human beings. The reference value was found to be independent of age (16-65 years) and sex. Using the discrimination value for serum glycogen phosphorylase activity at 3 nkat/l serum two groups of patients suffering either from acute myocardial infarction (n = 79) or chronic ischemic heart disease (n = 92) were separated with a diagnostic sensitivity and specificity of 0.91 and 0.93, respectively, of this diagnostic tool.