COMPARISONS OF NONINVASIVE BONE-MINERAL MEASUREMENTS IN ASSESSING AGE-RELATED LOSS, FRACTURE DISCRIMINATION, AND DIAGNOSTIC CLASSIFICATION

The purpose of this study was to examine the commonly available method s of noninvasively assessing bone mineral status across three defined female populations to examine their interrelationships, compare their respective abilities to reflect age- and menopause-related bone loss, discriminate osteoporotic fractures, and classify patients diagnostica lly. A total of 47 healthy premenopausal (age 33 +/- 7 years), 41 heal thy postmenopausal (age 64 +/- 9 years), and 36 osteoporotic postmenop ausal (age 70 +/- 6 years) women were examined with the following tech niques: (1) quantitative computed tomography of the L1-L4 lumbar spine for trabecular (QCT TRAB BMD) and integral (QCT INTG BMD) bone minera l density (BMD); (2) dual X-ray absorptiometry of the L1-L4 posterior- anterior (DXA PA BMD) and L2-L4 lateral (DXA LAT BMD) lumbar spine, of the femoral neck (DXA NECK BMD) and trochanter (DXA TROC BMD), and of the ultradistal radius (DXA UD BMD) for integral BMD; (3) peripheral QCT of the distal radius for trabecular BMD (pQCT TRAB BMD) and cortic al bone mineral content (BMC) (pQCT CORT BMC); (4) two radiographic ab sorptiometric techniques of the metacarpal (RA METC BMD) and phalanges (RA PHAL BMD) for integral BMD; and (5) two quantitative ultrasound d evices (QUS) of the calcaneus for speed of sound (SOS CALC) and broadb and ultrasound attenuation (BUA CALC). In general, correlations ranged from (r = 0.10-0.93) among different sites and techniques. We found t hat pQCT TRAB BMD correlated poorly (r less than or equal to 0.46) wit h all other measurements except DXA UD BMD (r = 0.62, p less than or e qual to 0.0001) and RA PHAL BMD (r = 0.52, p less than or equal to 0.0 001). The strongest correlation across techniques was between QCT INT BMD and DXA LAT BMD (r = 0.87, p less than or equal to 0.0001), and th e weakest correlation within a technique was between pQCT TRAB BMD and pQCT CORT BMC (r = 0.25, p less than or equal to 0.05). Techniques sh owing the highest correlations with age in the healthy groups also sho wed the greatest differences among groups. They also showed the best d iscrimination (as measured by the odds ratios) for the distinction bet ween healthy postmenopausal and osteoporotic postmenopausal groups bas ed on age-adjusted logistic regression analysis. For each anatomic sit e, the techniques providing the best results were: (1) spine, QCT TRAB BMD (annual loss, -1.2% [healthy premenopausal and healthy postmenopa usal]); Student's t-value [not the T score], 5.4 [healthy postmenopaus al vs. osteoporotic postmenopausal]; odds ratio, 4.3 [age-adjusted log istic regression for healthy postmenopausal vs. osteoporotic postmenop ausal]); (2) hip, DXA TROC BMD (-0.46; 3.5; 2.2); (3) radius, DXA UD B MD (-0.44; 3.3; 1.9) and pQCT, CORT BMC (-0.72; 2.9; 1.7); (4) hand, R A PHAL (-0.51; 3.6; 2.0); and (5) calcaneus, SOS (-0.09; 3.4; 2.1) and BUA (-0.52; 2.6; 1.7). Despite these performance trends, the differen ces among sites and techniques were statistically insignificant (p > 0 .05) using age-adjusted receiver operating characteristic (ROC) curve analysis. Nevertheless, kappa score analysis (using -2.0 T score as th e cut-off value for osteopenia and -2.5 T score for osteoporosis) show ed that in general the diagnostic agreement among these measurements i n classifying women as osteopenic or osteoporotic was poor, with kappa scores averaging about 0.4 (exceptions were QCT TRAB/INTG BMD, DXA LA T BMD, and RA PHAL BMD, with kappa scores ranging from 0.63 to 0.89). Often different patients were estimated at risk by using different mea surement sites or techniques.