Assessment of osteoporosis by quantitative ultrasound versus dual energy X-ray absorptiometry in children with chronic rheumatic diseases.

OBJECTIVE To evaluate the validity of quantitative ultrasound bone sonometry (QUBS) as a screening tool for the diagnosis of osteoporosis in children with chronic rheumatic diseases (CRD), compared to the conventional dual energy x-ray absorptiometry (DEXA). METHODS Forty children with CRD [32 with juvenile idiopathic arthritis (JIA), 6 with systemic lupus erythematosus, and 2 with dermatomyositis] aged 9.9 +/- 4.3 years, were evaluated by QUBS of radius and tibia and DEXA of the lumbar spine. Twenty-five (62.5%) patients were treated with corticosteroids. Measurements of the velocity of the ultrasound wave, expressed as speed of sound (SOS) in m/s, and the results of the bone mineral density (BMD) assessed by DEXA were compared to reference data from healthy age and sex matched Israeli children. RESULTS Compared to controls, patients with CRD had significantly lower values by QUBS and DEXA alike. BMD and SOS z scores < -1 SD were found in 45% and 38% of the patients, respectively. Reduced BMD and SOS values correlated with age at disease onset and corticosteroid treatment. BMD alone correlated negatively with disease duration and methotrexate therapy. BMD was significantly lower in patients with polyarticular JIA compared to patients with oligoarticular disease (p < 0.03). SOS values did not differ between subtypes of JIA. A significant positive correlation was found between the lumbar DEXA and radius SOS. CONCLUSION QUBS evaluation of radius and tibia yielded results comparable to DEXA and may therefore be used for screening patients with CRD for osteoporosis. QUBS might represent a promising means of evaluating bone quality in at-risk children.