Correlating Whole-Body Bone Mineral Densitometry Measurements to Those From Local Anatomical Sites

BACKGROUND: Using the same cutoff points for whole-body measurements as for site-specific measurements will result in underestimation of osteoporosis. OBJECTIVES: We assessed the correlation between densitometry measurements for the whole body with those for the femur, lumbar spine, and forearm to evaluate the possibility of replacing site-specific values with whole-body measurements. PATIENTS AND METHODS: In this cross-sectional study, we evaluated all patients referred to a single rheumatology clinic for bone mineral density measurements from 2009 to 2010. All patients who had bone mineral density measurements taken from the hip, lumbar spine, forearm, and whole body were enrolled in the study. Standard bone mineral density measurements were performed using a dual energy X-ray absorptiometry device (Hologic Delphi A; Hologic, Bedford, MA, USA). Bone mineral density, Z-score, and T-score were measured for all patients and all body regions. RESULTS: The mean age of the 152 participating patients was 56.7 ± 12.6 years, and 97.4% were female. Pearson correlation coefficients of the whole-body bone mineral density values compared with site-specific values in patients over age 50 were 0.66 – 0.75. Using T-score cutoff points of -1 and -2.5 for osteopenia and osteoporosis, whole-body measurements underestimated the percentage of abnormal patients compared with the site-specific measurements (all P < 0.001). Using receiver operating characteristic (ROC) analysis, the whole-body bone mineral density showed respective areas under the curve of 0.96 and 0.84 for the diagnosis of abnormal hip bone mineral density and osteoporosis. CONCLUSION: Using the same cutoff points for whole-body measurements as for site-specific measurements will result in overestimation or especially underestimation of osteopenia and osteoporosis diagnosis. Choosing new and appropriate cutoff points for whole-body densitometric measurements when we want to substitutes this assessment instead of site specific measurements seems mandatory and will decrease the rate of false diagnoses of densitometric deficiencies in these anatomical sites.