Identification of men with reduced bone density at the lumbar spine and femoral neck using BMD of the os calcis.

We assessed the utility of os calcis (OC) bone mineral density (BMD) measurements to identify men with low BMD at the lumbar spine (LS) and femoral neck (FN). BMD was measured by dual X-ray absorptiometry (DXA). Receiver operator characteristics (ROC) analysis was applied to determine the risk of osteoporosis at the lumbar spine or femoral neck. [A total of 230 men with an average age of 59 yr were studied.] The most common reasons for referral were fracture (47%) and steroid use (46%). Twenty-six percent were osteoporotic at the LS, 21% at the FN, and 15% at the OC. Optimal classification with respect to osteoporotic measurements at the LS or FN was obtained at an OC T-score of -1.9 (BMD = 0.45 g/cm2). Osteoporosis was only weakly related to a simple cumulative risk factor score, but was strongly related to a T-score OC categorized into quartiles. Regression analysis of BMD on the major risk factors alone explained only 17% of the variance in BMD at the LS and 5% at the FN. The combination of the T-score at the OC, age, and weight provided the best model. BMD OC is superior to risk factors alone in the clinical evaluation and selection of men referred for axial densitometry.