Comparison between calcaneus quantitative ultrasound and the gold standard DXA in the ability to detect osteoporosis in chronic obstructive pulmonary disease patients

Background Osteoporosis is a prevalent comorbidity in patients with COPD that is usually underrecognized and hence, undertreated. Compared to the gold standard dual-energy X-ray absorptiometry (DXA), calcaneus quantitative ultrasound (QUS) is less expensive, more portable, and more accessible, especially in less developed countries. The aim of this study was to investigate the ability of calcaneus QUS to screen and prescreen for osteoporosis in patients with COPD. Methods This cross-sectional study enrolled 67 males older than 50 years with clinically stable COPD. DXA scans of the lumbar spine (L2–4) and femoral neck were performed. QUS of the right calcaneus (AOS-100) was used to assess the broadband ultrasound attenuation (BUA), speed of sound (SOS), osteo sono-assessment index (OSI), and T-score. When the T-score was ≤ − 2.5, osteoporosis was diagnosed by both DXA and QUS. Results Forty-eight patients (71.6%) had DXA T-scores ≤ − 2.5 at either the lumbar spine or femoral neck. All QUS parameters (BUA, SOS, OSI, and T-score) could discriminate DXA-determined osteoporosis (the area under the curve varied from 0.64 to 0.83). The QUS T-score was significantly moderately correlated with the DXA T-score at both the femoral neck ( r = 0.55) and lumbar spine ( r = 0.52). The sensitivity and specificity of QUS in identifying osteoporosis were 10.4% and 94.7%, respectively. The positive and negative predictive values were 83.3% and 29.5%, respectively. When a QUS T-score of 0.09 was used as the cutoff, the sensitivity exceeded 90%, and 15% of the DXA scans were not warranted. Conclusions The sensitivity and specificity of calcaneus QUS were not sufficient for QUS to be used as an alternative to DXA for osteoporosis screening. However, QUS may be useful for prescreening before DXA to identify COPD patients who have either a high or low likelihood of osteoporosis. Consequently, QUS reduces the need for DXA referral.