Comparison of peripheral forearm DXA and clinical risk factor screening using FRAX® to assess the risk of HIV-associated low bone mass: a cross-sectional study

There is growing awareness that HIV infection is associated with low bone mass and fracture. DXA is a relatively scarce resource. Therefore, we evaluated two tools: peripheral DXA (pDXA) at the forearm and Fracture Risk Assessment Tool (FRAX®) to see which performed best at identifying men who should undergo DXA. In this setting, neither pDXA nor FRAX® showed good sensitivity and specificity for DXA.

Infection with human immunodeficiency virus (HIV) is associated with an increased risk of low bone mineral density (BMD) and fractures. European guidance advocates screening using the FRAX® tool at diagnosis, on initiation of antiretroviral therapy and biannually thereafter in order to decide the need for DXA scanning. This cross-sectional study evaluates the performance of FRAX® and compares its sensitivity and specificity with that of another screening tool, peripheral forearm DXA (pDXA).

HIV-infected men with varying exposure to antiretroviral therapies were recruited. FRAX® scores were calculated for all participants and everybody underwent pDXA scanning. Femoral neck and lumbar spine BMD was acquired on a Hologic QDR machine by an assessor blinded to the results of the FRAX® and pDXA.

One hundred and sixty-eight men (median age 45 years) were recruited with a median duration since HIV diagnosis of 74 months. In total, 21 % of subjects had either osteoporosis (aged ≥50 years) or BMD lower than expected for age (aged <50 years), according to axial DXA. Using a pDXA screening threshold of T ≤ -0.9, sensitivity was high (91 %) in defining those with the worst BMD on axial DXA but with poorer specificity (33 %). Alternately, using a threshold of T ≤ -2.7 reduced sensitivity (34 %) with an increase in specificity (91 %). FRAX® with HIV included as a secondary risk factor had poor sensitivity (31 %) and specificity (74 %) for detecting those with the poorest BMD on axial DXA.

In this setting, neither pDXA scanning nor FRAX® was sensitive and specific for low bone mass on DXA and neither was performance much improved by using both screening tools. Prospective studies with fracture as an outcome are required in HIV.