BONE DENSITOMETRY - COMPARISON OF DUAL-ENERGY X-RAY ABSORPTIOMETRY TORADIOGRAPHIC ABSORPTIOMETRY

Objective. To assess the reliability and validity of radiographic abso rptiometry of middle phalanges when compared to dual energy x-ray abso rptiometry (DEXA) of the spine and hip as an indicator of osteoporosis . Methods. DEXA readings from the spine and femur were compared with r adiographic absorptiometry measurements obtained the same day in a sam ple of 50 women (average age 63 yrs; range 23-86). Results. Both spine and femur DEX-A scores were significantly correlated with radiographi c absorptiometry scores (R = 0.70 and 0.65, respectively; approximate standard errors 0.08), DEXA scores were Used as the standard, defining moderate fracture risk by a standardized t score < -2 and marked risk by t < -3, Using cutpoints of t < -2 for DEXA and t < -3 for standard ized radiographic absorptiometry values, the sensitivity to osteopenia was 0.62 for DEXA of the spine and 0.63 for DEXA of the femur, with s pecificities of 0.90 and 0.96, respectively, at these cutpoints; the c orresponding false positive and false negative rates for our cohort of women were 0.19 and 0.24 (spine) and 0.07 and 0.24 (femur). Receiver operating characteristic (ROC) curves were plotted, varying DEXA measu rement site from spine to femur and standardized cutoff from -2 to -3; the areas under the resulting ROC curves ranged from 0.82 to 0.91. Co nclusion. Radiographic absorptiometry holds promise as a practical met hod for screening for osteoporosis.