Quantitative Computerized Tomography (QCT) versus Dual X-Ray Absorptiometry (DXA) in the Assessment of Bone Mineral Density of HIV-1 Infected Children

Bone studies of HIV-infected children using dual X-ray absorptiometry (DXA) suggest bone mineral density (BMD) abnormalities. Pediatric studies are often performed using DXA instead of computed tomography (CT), which accounts for 3-dimensional differences in bone size of growing children. We evaluated whether CT would match DXA measurements in this population. For this purpose, the BMD of 16 perinatally HIV-infected patients, ages 6 to 22 was assessed. Subjects were matched by age, gender, and race to controls. BMD was assessed via DXA and QCT. Clinical anthropometric data, body mass index, immunologic and virologic parameters and laboratory markers for osteoblastic and osteoclastic activity were performed. No statistically significant differences in age and anthropometric parameters between subjects and controls were found. Individual CT and DXA z-scores were significantly different when subjects were evaluated as a group (p = 0.0002) or when males and females were analyzed independently (p = 0.001 and 0.03). DXA z-scores were below 1 SD, while CT z-scores were above the mean. 31% of subjects were identified as having poor bone mineralization by DXA while none had osteopenia/osteoporosis by CT. There was no correlation between immunologic/virologic parameters and BMD by either method. Increased osteoclastic activity was noted in 10 patients receiving tenofovir. In summary, decreased BMD diagnosed by DXA in pediatric HIV-infected subjects was not confirmed by CT. Increased bone turnover in patients on tenofovir was suggested by laboratory markers. Prospective studies using CT as the imaging standard are needed for evaluation of bone mineral changes in HIV-infected children.