Bone alkaline phosphatase isoenzyme and urinary hydroxyproline in healthy subjects, patients with osteolytic metastases, and patients with primary hyperparathyroidism.

The values of urinary hydroxyproline excretion reflecting the bone remodelling by osteoclasts, and the bone isoenzyme of serum alkaline phosphatase reflecting the osteoblastic function, in 100 randomly selected healthy subjects, 100 patients with primary hyperparathyroidism, and 100 patients with osteolytic secondary tumorous deposits in the skeleton showed a bivariate lognormal distribution. Hotelling's test revealed highly significant differences in the biochemical values among these three conditions, even when Bonferroni's modification of the test was used. The individual biochemical values, however, displayed many mutual overlaps. Despite this, the discriminatory analysis based on bivariate biochemical data resulted in a correct diagnosis in all healthy subjects, in 82 patients with primary hyperparathyroidism, and in 93 patients with osteolytic metastases. The simultaneous determinations of urinary hydroxyproline excretion and the bone alkaline phosphatase insoenzyme improve the differential diagnosis between these conditions. The predominance of urinary hydroxyproline excretion relative to bone alkaline phosphatase isoenzyme suggests an osteolytic metastasis. Proportionately elevated both hydroxyproline and bone alkaline phosphatase isoenzyme indicate the presence of primary hyperparathyroidism. This shows the importance of a correct biometrical processing of data. Nevertheless, a complex clinical evaluation is always mandatory.