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PURPOSE We aimed define thresholds for HU values observed on opportunistic CT scans that suggest abnormal bone mineral density (BMD) in a heterogeneous Middle Eastern population. METHODS Consecutive patients who had undergone CT and dual-energy X-ray absorptiometry (DXA) test of the lumbar spine within 6 months were included in this retrospective study. Hounsfield units (HU) on lateral lumbar spine CT and BMD at the spine and hip on DXA were compared. Potential HU thresholds suggestive of abnormal BMD were established using receiver operating characteristic (ROC) analysis. RESULTS 246 patients (mean age of 64 ± 11.6 years; 83 % female) were included. On DXA, 27 % had osteoporosis, 56 % had osteopenia, and 17 % had normal BMD. To distinguish osteoporosis from non-osteoporosis (osteopenia, normal BMD), a threshold of HU160 had sensitivity 95 % and the balanced threshold was HU121 (sensitivity 74 %, specificity 61 %). To distinguish normal from abnormal BMD (osteoporosis, osteopenia), a threshold of HU110 had specificity 93 % and the balanced threshold was HU149 (sensitivity 76 %, specificity 74 %). CONCLUSIONS In a heterogeneous Middle-Eastern population, our study supports the reported correlation between HU values on lumbar spine CT and BMD on DXA. In this population, HU > 160 correlates with low probability of osteoporosis on DXA, and screening examination is not warranted unless a vertebral fracture is detected; for HU ≤ 110 there is high probability of abnormal (osteoporosis or osteopenia) BMD, DXA examination is warranted; Finally, for HU 110-160, there is an intermediate chance of abnormal BMD, DXA examination may be warranted in specific patients with other risk factors.