[Quantitative ultrasound scans of the calcaneus: a useful tool for screening osteoporosis in patients with connective tissue disease]

Abstract

Objective: To evaluate the ability of calcaneus quantitative ultrasound (QUS) to diagnose osteoporosis in connective tissue disease (CTD) patients.

Methods: In the study, 126 female patients with established CTD underwent dual-energy X-ray absorptiometry (DXA) of the lumber and right hip and QUS of the right heel at the same time. Sensitivity, specificity, as well as positive and negative predictive values were calculated to determine the correlation between cases of osteoporosis detected by the QUS heel scan and by DXA.

Results: The mean age of the 126 patients was (43.4 ± 19.8) years (ranging from 30.0 to 80.0 years). Based on their DXA data, 36 (28.6%) patients had normal bone mineral density (BMD, T score ≥ -1.0), 90 (71.4%) patients had abnormal BMD. In abnormal BMD patients, 45 (35.7%) had osteopenia (-2.5 < T score<-1.0), and 42 (33.3%) were osteoporotic (T score ≤ -2.5), while 3 (2.4%) patients had fragile fracture. Broadband ultrasound attenuation (BUA), speed of sound (SOS) and stiffness index (SI) were all significantly different between osteopenia and the normal group when scanning with QUS. QUS T score was positively correlated with DXA T score, both at lumber and right hip respectively (r=0.491, 0.648, P<0.01). After correction by age and BMI, QUS T score remained positively correlated with DXA T score by partial correlation analysis (Pearson partial vertebral r=0.430, P=0.006; right hip r=0.593, P<0.001). The area under the ROC curve for diagnosis of lumber and hip osteoporosis were 0.836 (95%CI: 0.695, 0.977) and 0.647 (95%CI: 0.579, 0.957) separately. The sensitivity and specificity for identifying osteoporosis in lumber were 70% and 83.3% respectively when the T score threshold of QUS was defined as -1.5; however, the sensitivity and the specificity for identifying osteoporosis at right hip were 72.7% and 88.9% when T score threshold of QUS was defined as -1.85. The best SI threshold was defined as 76 for identifying osteoporosis, with sensitivity being 0.800 and specificity 0.741.

Conclusion: Our study confirmed that QUS measurements performed at calcaneus with quantitative ultrasound bone analysis were capable of screening osteoporosis defined by axial BMD using DXA in female CTD patients.