[Differences in the frequency of osteoporosis according to the skeletal site evaluated. Analysis in 987 Spanish postmenopausal women referred to a bone densitometry unit].

OBJECTIVE To analyze the differences in the frequency of osteoporosis according to the skeletal site evaluated in a group of Spanish postmenopausal women. METHODS We reviewed the data of 987 postmenopausal women (mean age, 53.8±5.5 years). BMD status was evaluated by DXA. We used the WHO thresholds to classify the patients. T-score was obtained from the single evaluation of each lumbar vertebra (L2, L3 and L4), the mean value of lumbar spine (L2-L4), femoral neck and total hip. RESULTS In 144 (14.7%) women, discrepancies were observed when we considered the single vertebral analysis versus the L2-L4 analysis; 62 (6%) women who presented osteoporosis in at least one vertebra would have been due to the osteopenia category when L2-L4 value was selected. In 271 (27.8%) women, discrepancies were observed when we considered the total hip analysis versus the femoral neck analysis. The frequency of osteoporosis ranged from 3% when only the analysis of the total hip was considered to 16% when the results of L2-L4 and proximal femur (total hip or femoral neck) measurements were selected. CONCLUSIONS Frequency of osteoporosis varies notably according to the skeletal zone considered.