Poor correlations between measurements of bone quality by quantitative ultrasound sonography and dual energy X-ray absorptiometry in patients with β-thalassaemia major

Osteopenia/osteoporosis is a major component of morbidity even in young patients with beta-thalassaemia major. Dual energy X-ray absorptiometry (DXA) is the reference method for determining bone mineral density (BMD). Quantitative ultrasound sonography (QUS) for bone measurement is a relatively new, inexpensive and radiation-free method that could serve as an alternative to DXA. Our aim was to assess bone status in thalassaemic patients both with QUS and DXA and, consequently, to investigate the degree of correlation between the two methods. Thirty-three patients (15 male and 18 female) with beta-thalassaemia major, regularly transfused and systematically iron-chelated, participated in the study. Mean age was 22.0 +/- 8.0 yr (range: 6.5-41.0 yr). All patients were evaluated with QUS at radius and tibia and had DXA scan at lumbar spine vertebrae (L2-L4), whereas 20 patients were additionally assessed with DXA at the left hip (femoral neck, trochanter region and Ward's triangle). Results were expressed as Z-scores compared with sex- and age-matched population. Lowest mean Z-scores measured with DXA were recorded at lumbar spine and Ward's triangle (-1.1 +/- 1.13 and -0.95 +/- 1.07, respectively). Lowest mean QUS-derived Z-scores were measured at radius, statistically significant compared with Z-scores measured at tibia (-0.6 +/- 1.1 vs. 0.4 +/- 1.1, P < 0.001). QUS measurements at radius were significantly correlated to QUS measurements at tibia (r = 0.51, P = 0.002). The latter were correlated to BMD measured at lumbar spine (r = 0.516, P = 0.002) and at trochanter region (r = 0.646, P = 0.003). All BMD measurements at hip were significantly correlated to each other. Lumbar spine BMD was correlated to BMD at femoral neck (r = 0.607, P = 0.003) and to BMD at Ward's triangle (r = 0.438, P = 0.027). Finally, no agreement was recorded between the two methods in identifying thalassaemic patients at risk for osteoporosis (kappa = 0.203, P = 0.04). Quantitative ultrasound sonography could not serve as an alternate to DXA.