Normalization of bone mineral content to height, weight, and lean body mass: implications for clinical use

The main object of the present study was to reduce the large biological variation in forearm bone mineral content (BMC) by correction for individual variation in gross morphology. In 315 normal females aged 45--54 years, determinations of height, weight, and 24-h urinary creatinine excretion rates were performed, and lean body mass was calculated, BMC was measured by photon absorptiometry on both forearms. BMC was correlated to height (r = 0.19, P less than 0.01), to weight (r = 0.09, P greater than 0.05), to lean body mass (r = 0.15, P less than 0.05), and to creatinine excretion rate (r = 0.29, P less than 0.001). The biological variation in BMC of the 315 females was for raw BMC 15.8%; after correction of BMC for height 15.5%, for weight 15.8%, for lean body mass 15.6%, and for creatinine excretion rate 15.2%. Regression analysis with two independent variables (creatinine excretion and height or weight) increased in both cases the correlation coefficient to 0.32 and decreased the interindividual coefficient of variation of BMC to 15.0%. For diagnostic purposes BMC must be corrected for age and sex, but further corrections seem of minimal benefit.