Screening for osteoporosis in Crohn's disease. A detailed evaluation of calcaneal ultrasound.

OBJECTIVES: To compare calcaneal broadband ultrasonic attenuation (BUA) and velocity of sound (VOS) in patients with Crohn's disease with an age-matched control population. The validity of BUA as a screening tool for osteoporosis was evaluated and the relationship between BUA and previous fracture studied. DESIGN: Cross-sectional study. BACKGROUND: Since patients with Crohn's disease are at risk of osteoporosis and premature fracture, routine assessment of bone mineral density (BMD) is recommended. Quantitative ultrasound of the calcaneum is an inexpensive and radiation-free means of assessing bone density which also provides information on bone microstructure. METHODS: BUA (dB/MHz) and VOS (m/s) were measured at the calcaneum (CUBAclinical, McCue Ultrasonics, Winchester, UK) and compared with bone mineral density at the hip and lumbar spine measured by dual-energy X-ray absorptiometry (DEXA); 100 patients (42 men) with Crohn's disease and 52 age-matched healthy controls (23 men) were studied. RESULTS: BUA was significantly reduced in patients with Crohn's disease compared with age-matched controls [76.53 dB/MHz (+/-17.3) vs 87.29 dB/MHz (+/-17.9), difference in means = 10.76, 95% CI -16.67, -4.85, P = 0.0004] and was significantly associated with BMD at the spine (r = 0.49, 95% CI 0.32, 0.63, P< 0.0001) and femoral neck (r = 0.54, 95% CI 0.38, 0.67, P < 0.0001). In the diagnosis of osteoporosis (t score <-2.5) BUA had a sensitivity of 66.7% at the femoral neck, with a specificity of 85.6%; sensitivity of BUA at the spine was 75% with specificity 89%. CONCLUSION: Patients with Crohn's disease have reduced BUA compared with an age-matched control population. Calcaneal BUA is significantly associated with BMD at the hip and spine but the correlation is insufficient to recommend ultrasound as a screening tool for DEXA.