Patients with rheumatoid arthritis are recognized as being at risk for osteoporosis as a result of the disease process as well as the medication used to treat it. This study was conducted to consider the use of calcaneal scanning with quantitative ultrasound-contact ultrasound bone analysis (CUBA)-to diagnose osteoporosis in patients with rheumatoid arthritis.
Forty-six patients (11 men and 35 women) with established rheumatoid arthritis underwent dual-energy x-ray absorptiometry (DEXA) of the nondominant wrist and CUBA of the nondominant heel. Sensitivity, specificity, and positive and negative predictive values were used to determine the correlation between osteoporosis as diagnosed by the CUBA heel scan compared with the DEXA wrist scan given that DEXA is widely seen as the gold standard for the diagnosis of osteoporosis.
The CUBA heel scan revealed a sensitivity of 90% and a specificity of 44% for a diagnosis of osteoporosis compared with DEXA. The positive predictive value of the CUBA scan was 31%, and the negative predictive value was 94%. Therefore, if normal bone density is found using CUBA, there is 94% certainty this is correct. However, if osteoporosis is diagnosed using CUBA, there is only 31% certainty this is correct. In such instances a secondary scan using a different method (eg, DEXA) would be required. Future work should consider the effect of minor alterations to the equipment or scanning protocol, because this may improve diagnosis.
The CUBA unit could be used as a primary screening device. Given the cost and accessibility issues associated with DEXA, quantitative ultrasound may have a role in screening for osteoporosis in the primary-care setting to determine the most appropriate routes of referral for patients requiring further investigations.