Validity of bone mineral density measurements in distal sites as an indicator of total bone mineral density in a group of pre-adolescent and adolescent women

BACKGROUND: The study of bone mineral density (BMD) has received attention due to the importance of osteoporosis as a public health problem in Mexico. The objective of this study was to assess the validity of BMD measures in distal forearm and calcaneus with portable densitometers as indicators of BMD on other anatomic sites. METHODS: We conducted a cross-sectional study with 219 women from 9 to 22 years of age in Cuernavaca, Morelos, Mexico. We measured BMD in central sites (the entire skeleton, excluding head, proximal femur, and lumbar spine) using dual X-ray absorptiometry (DXA) and in peripheral sites (distal forearm and calcaneus) using a portable densitometer with DXA technology. Measurements of height, weight, body composition, physical activity, and demographic characteristics were collected. Agreement of measurements of BMD was assessed using correlation and regression analysis, and the method proposed by Bland and Altman. RESULTS: Higher levels of BMD were found in total skeleton (0.88 g/cm(2)) than in calcaneus (0.48 g/cm(2)) and distal forearm (0.38 g/cm(2)) (p <0.05). Moderate-to-high positive correlation coefficients (all significant) (p <0.05) were found between BMD in distal forearm and calcaneus vs. central anatomic sites, ranging from r = 0.49 to r = 0.78. BMD was higher in central sites compared with distal forearm and calcaneus. CONCLUSIONS: Measurement of BMD in distal forearm and calcaneus with portable densitometers provided valid indicators of BMD in central anatomic sites among pre-adolescent and adolescent women in Mexico.