A comparative study was performed on the sensitivity of the determination of the available biochemical markers of bone formation - total and bone alkaline phosphatase (TAP and bAP, respectively), osteocalcin (BGP), procollagen I aminoterminal propeptide (PINP) and procollagen I carboxyterminal propeptide (PICP) - in the study of postmenopausal osteoporosis. The comparison between PINP and PICP, due to the recent development of the amino-terminal assay, is of special interest. The study included 26 untreated osteoporotic postmenopausal women, age 59 +/- 6 years (range 46-69 years) and 17 healthy control postmenopausal women, age 56 +/- 7 years (range 48-70 years). We found a significant increase in the levels of bAP (p = 0.0021), BGP (p = 0.041), PINP (p = 0.0001) and PICP (p = 0.0073), but not in the levels of TAP (p = 0.3389), in osteoporotic patients with respect to the control group. Serum PINP and bAP showed the highest diagnostic accuracy among the markers of bone formation studied, as can be deduced from the receiver operating characteristics (ROC) curves. In spite of their similar origin (amino-terminal and carboxy-terminal release from a procollagen molecule), the results obtained by measuring levels of PINP are significantly better than those found with PICP.
