More on Total and Bone-Specific Alkaline Phosphatase

Abstract

Having read with interest a recent article by Woitge et al. (1) on the clinical utility of different bone alkaline phosphatase (BAP) assays, I would like to discuss some of their findings. 1. The authors report a lack of significant differences in BAP values, as measured by IRMA (“Ostase”), between pre- and postmenopausal women. However, other groups using the same immunoassay found mean increases ranging from 43% to 104% (2)(3)(4)(5). This is in contrast to the authors’ proposal (1) that BAP mass and enzyme activity behave differently. The necessity for studies with larger numbers of participants is given to verify the true physiological changes. 2. Woitge et al. observed higher BAP activities in men than in premenopausal women but no significant difference in BAP mass concentrations. In contrast, my colleagues and I have found a clear sex-related difference in BAP activity (6) and mass concentrations (7). Without stratifying the reference group according to age and menopausal status, others (5)(8)(9) have also reported a lack of sex-related differences in BAP mass concentrations; however, this may instead reflect a postmenopausal increase in bone turnover so that BAP concentrations in females attain the values seen in males. 3. In patients with chronic hepatic failure (and no evidence of metabolic bone disease) a BAP enzyme immunoassay (“Alkphase-B”) was the only alkaline phosphatase assay showing a lack of significant increase in BAP in women over the values seen in the male … [↵][1]aAuthor for correspondence. [1]: #xref-corresp-1-1