Site-discordance in bone mineral density (BMD) assessment is common and affects patient categorization. Greater number of osteoporotic sites correlates with lower T score at each index site. The effect of BMD measurement at the contralateral femur on osteoporosis diagnosis has been previously evaluated.
The aim of the study was to investigate the effect of BMD measurement at the contralateral femur on osteoporosis diagnosis.
Methods: BMD of the lumbar spine and both femurs was measured by dual energy X-ray absorptiometry in 93 consecutive Caucasian women aged≥50 years (62.4±8.7 (mean±S.D.) years) with a body mass index of 29.2±4.5 (range 20.845.2). Using the T score from each site, measurements were classified according to the WHO criteria for the diagnosis of osteoporosis as normal, if T score >−1, osteopenia, if T score<−1 and osteoporosis, if T score <−2.5. The results from the three skeleton sites were compared to each other using the statistical package SPSS and the effect of the inclusion of the contralateral femur on the diagnosis of osteoporosis was determined.
Results: BMD did not differ between the two femurs (P>0.05, paired Students t-test). In 77 (82.8%) of the women the classification would be the same if either two or three sites were measured. In 16 (17.2%) of the women the classification would be affected by the measurement of the contralateral femur. In 8 (8.6%) of them T score of the lumbar spine was equal or lower than that of both femurs, thus lumbar spine measurement determined the diagnosis. In the remaining 8 (8.6%) classification depended on the choice of the femur measured and would be different if only the right or left femur was measured.
Conclusions: BMD measurement was not different between the femurs. Although the number of cases included is small, it appears that determining BMD at the lumbar spine and one femur is enough for a correct evaluation and diagnosis in the majority of the patients (90%). Nevertheless, in a small number of patients the choice of the femur measured may affect patient diagnosis and classification.