3159 Bone Turnover Biomarkers May Discriminate Low Bone Mineral Density in HIV-Infected Adults

Abstract

OBJECTIVES/SPECIFIC AIMS: Persons living with HIV (PLWH) are at increased risk for fragility bone disease. Current osteoporosis screening guidelines do not account for HIV status, and clinical risk assessment tools are not sensitive in PLWH. We examined the value of traditional osteoporosis risk factors, HIV-specific indices, and bone turnover biomarkers in predicting low bone mineral density (BMD) in PLWH. METHODS/STUDY POPULATION: Demographic and clinical characteristics, dual energy x-ray absorptiometry (DXA)-derived BMD, HIV indices (viral load, CD4 count, antiretroviral therapy [ART]), and biomarkers of bone turnover (C-terminal telopeptide of collagen [CTx], osteocalcin [OCN]) were evaluated in a cross-sectional analysis of PLWH (n=248) and HIV- controls (n=183). The primary outcome was low BMD, defined as osteopenia or osteoporosis by WHO criteria. Multivariable logistic and modified Poisson regression models were used to assess associations between low BMD and covariates of interest. RESULTS/ANTICIPATED RESULTS: Overall, median age was 44 years, 48% were male, 88% were black, median body mass index (BMI) was 28 kg/m2, 72% smoked cigarettes, and 53% used alcohol; characteristics did not differ by HIV status. PLWH had a mean CD4 of 408 cells/mm3, 55% were ART-naïve, and 45% had viral suppression on ART. Overall, 25% (109/431) had low BMD, including 31% of PLWH compared to 16% of HIV- controls. In multivariable models, HIV was significantly associated with low BMD (aOR 2.46, 95%CI 1.39-4.34; aRR 1.90, 95%CI 1.18-3.07). Adjusting for HIV, three traditional risks– age, race, and BMI– were independently associated with low BMD in the full cohort. However, bone turnover markers, CTx and OCN, were better able to discriminate low vs. normal BMD in PLWH compared to HIV- controls. In PLWH, mean serum CTx was 23% higher in low vs. normal BMD (mean CTx difference=0.06 ug/mL); in HIV- controls, no association with BMD was observed (mean CTx difference=0 ug/mL). In PLWH, mean serum OCN was 38% higher in those with low vs. normal BMD (mean OCN difference=2.48 ug/mL); in HIV- controls, mean serum OCN was only 16% higher in those with low vs. normal BMD (mean OCN difference=1.08 ug/mL). DISCUSSION/SIGNIFICANCE OF IMPACT: In PLWH as opposed to HIV- controls, serum biomarkers reflecting a high bone turnover state, may discriminate individuals with low versus normal BMD. Because changes in biomarkers precede changes in BMD, these markers should be explored further either alone or in combination with traditional risk assessment tools to improve early screening for osteoporosis in PLWH.