Serum osteocalcin and procollagen as markers for the risk of osteoporotic fracture in corticosteroid-treated asthmatic adults

Background: Dual energy x-ray absorptiometry provides the definitive measur e of osteoporotic fracture risk. Objective: We sought to determine whether metabolic measures of bone format ion and/or common features of clinical hypercortisonism provide a useful gu ide in selecting corticosteroid-treated asthmatic patients for referral for bone densitometry, Methods: We measured bone density and 8 AM serum osteocalcin, procollagen, and cortisol levels in 52 asthmatic adults aged 60.7 +/- 12.6 years (mean /- SD), Years of steroid exposure for these patients was 11.8 +/- 10.7 (pre dnisone) and 11.78 +/- 4.98 (inhaled steroid). Using stepwise logistic regr ession, we assessed the capacity of the osteocalcin and procollagen levels, with or without the cortisol level, age, clinical features of hypercortiso nism, and different lifetime exposures to inhaled and oral steroids for dis tinguishing between patients with greater or lesser risk of fracture. Results: Osteoporosis, defined as a bone density T score below -2.5, affect ed 26% of the group at the spine and 63% at the hip, At the spine, greater risk was associated only with lower cortisol levels (P = .003), Diagnostic accuracy was 71%, the false-positive rate was 26%, and the false-negative r ate was 31%. At the hip, greater risk was associated with lower cortisol le vels (P = .002), longer prednisone exposure, (P = .003), loser current dose s of prednisone (P = .01) and inhaled steroid (P = .02), and older age (P = .01), Diagnostic accuracy was 83%, the false-positive rate was 13%, and th e false-negative rate was 21%, Conclusions: Neither osteocalcin nor procollagen nor any of the clinical cr iteria analyzed proved sufficiently accurate to be reliable as indicators o f the risk of fracture in these elderly, corticosteroid-treated asthmatic a dults. They are therefore not useful for selecting such patients for diagno stic densitometry.