ASSESSMENT OF SERUM TOTAL AND BONE ALKALINE-PHOSPHATASE MEASUREMENT IN CLINICAL-PRACTICE

The aim of the study was to measure serum levels of the bone-specific isoenzyme of alkaline phosphatase in normal subjects and patients with metabolic bone disease by using an immunoadsorption assay. We studied 140 healthy adults, 122 patients affected by metabolic bone disease a nd 15 patients with cholestatic liver disease. Mean values of the bone -specific isoenzyme of alkaline phosphatase in healthy men were signif icantly higher than those found in premenopausal women (17.8 +/- 4.2 U /l vs 15.6 +/- 4.6 U/l, p<0.02); postmenopausal women had significantl y higher levels of bone-specific isoenzyme of alkaline phosphatase (22 .6 +/- 6.4 U/l) than premenopausal women (p<0.0001). After the menopau se total alkaline phosphatase increased by 46 %, while the increase in bone-specific isoenzyme of alkaline phosphatase was 39 %. No signific ant correlations were found between bone-specific isoenzyme of alkalin e phosphatase and either age or years since menopause, in postmenopaus al subjects. In patients with bone-specific isoenzyme of alkaline phos phatase above the upper limit of normal, the assay had a sensitivity o f 100 % only in patients with Paget's disease of bone. In patients wit h cholestatic liver disease we found no correlation between bone-speci fic isoenzyme of alkaline phosphatase and either total alkaline phosph atase and gamma-glutamyl transpeptidase, while a positive correlation was found between total alkaline phosphatase and gamma-glutamyl transp eptidase. Our results confirm the role of bone-specific isoenzyme of a lkaline phosphatase assay in clinical research; however, its usefulnes s in clinical practice is unclear once liver involvement has been excl uded.