Background HIV-infected patients are at high risk of fragility fractures as they experience early decline in muscle mass and in bone mineral density (BMD), which is the most important independent risk factor for bone fragility. Several tools have been developed to identify subgroups at highest risk of low BMD. Most of them include well established determinants of BMD, as age and weight, but in the last years the potential independent role of lean mass has been speculated. Middle upper arm circumference (MUAC) highly correlates to skeletal muscle mass in HIV-infected males and EPIPOST [1], a tool developed to identify men in the general population with low BMD, supports that lean mass, indirectly measured by MUAC, is the best predictor of low BMD. We hypothesize that as HIV-infected patients experience sarcopenia, EPIPOST may be more suitable to identify low BMD in this population.

Objectives To evaluate the discriminatory capacity of Osteoporosis Screening Tool (OST; based on weight and age) and EPISPOT (based on MUAC) to identify low bone mineral density HIV-infected men.

Methods Cross-sectional evaluation of 118 HIV-infected Caucasian men, on combination antiretroviral therapy, followed in the Endocrinology outpatient clinic of São João Hospital Centre. Data on gender, age, weight, height, MUAC and femoral neck BMD (LUNAR EXPERT-XL) was collected. T-scores were calculated as recommended by the World Health Organization (the number of standard deviations (SD) by which an individual measurement differs from the mean value for healthy adult female population aged 30 years; the reference population were obtained from the NHANES III study). Patients with T-score <-1.0 were classified as having low BMD. Determination of the area under the ROC curve (AUC) was estimated to evaluate the discriminatory capacity of OST and EPIPOST. Sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) were calculated to the cut-off points suggested for the general Portuguese population [1].

Results Mean (SD) age was 48.5 (10.70) years-old and the prevalence of low BMD was 7.6% (n=9). The AUC for OST was 0.725 (p=0.025) and for EPIPOST was 0.776 (p=0.006). At the suggested cut-off points, OST (OST≤2) had a SE of 33.3%, a SP of 79.8%, a PPV of 12.0% and a NPV of 93.5%. At the suggested cut-off (EPIPOST> -2), EPIPOST had a SE of 100%, a SP of 3.6%, a PPV of 7.8% and a NPV of 100%.

Conclusions We conclude that, even though both tools show reasonable performance, EPIPOST has better discriminatory capacity than OST to identify HIV men with low bone mineral density. Although as screening tests both tools should identify the maximum of positive cases, the very high SE observed in EPIPOST is associated with an unacceptable specificity. This unbalance calls for calibration and determination of new EPIPOST cut-offs for HIV-infected men.

References

1. Vieira R. et al. Scientific Abstracts - Upper Arm Circumference Measurement Improves Screening for Low Bone Mineral Density in Men. Ann Rheum Dis. 2014;73(Suppl 2 770).

Disclosure of Interest None declared