Background
FRAXÂź is a validated, computer-based clinical fracture risk calculator that estimates 10-year risk of major osteoporotic (clinical spine, forearm, hip or shoulder) fracture, and hip fracture alone. It is widely used for decision-making in fracture prevention, but may underestimate risk in HIV-infected individuals. Some experts recommend considering HIV a cause of secondary osteoporosis when calculating FRAX in HIV-infected individuals.
Methods
From the Veterans Aging Study Virtual Cohort (VACS-VC), we included 24451 HIV-infected and uninfected 50-70 year old men with complete data in year 2000 to approximate all but two factors (i.e. history of secondary osteoporosis and parental hip fracture) for modified-FRAX calculation without bone density and 10-year observational data for incident fragility fracture. Accuracy of the modified-FRAX calculation was compared by observed/estimated (O/E) ratios of fracture by HIV status.
Results
Accuracy of modified-FRAX was less for HIV-infected (O/E=1.62, 95%CI: 1.45, 1.81) than uninfected men (O/E=1.29, 95%CI: 1.19, 1.40), but improved when HIV was included as a cause of secondary osteoporosis (O/E=1.20, 95%CI: 1.08, 1.34). However, only 3-6% of men with incident fractures were correctly identified by the modified-FRAX using accepted FRAX thresholds for pharmacologic therapy.
Conclusions
Modified-FRAX underestimated fracture rates more in older HIV-infected than otherwise similar uninfected men. Accuracy improved when HIV was included as a cause of secondary osteoporosis, but it still performed poorly for case-finding. Further studies are necessary to determine how to use FRAX or define an HIV-specific index to risk stratify for screening and treatment in older HIV-infected individuals.