Quantitative heel ultrasound in assessment of bone structure in renal transplant recipients

Many patients with advanced renal disease have osteopenia or even osteoporosis by the definition of the World Health Organization based on bone mineral density (BMD). Dual-energy X-ray absorptiometry (DXA), the standard method to assess BMD, is not always available. Quantitative heel ultrasound (QUS) is an inexpensive, mobile, and radiation-free diagnostic alternative, yet few data address this method's usefulness in patients with renal disease. The present study assessed the value of QUS in detecting changes in bone structure in renal transplant recipients compared with DXA. In a cross-sectional analysis, 50 patients (29 women) with a mean age of 50 +/- 13 years, mean time since transplantation of 60 months (range, 1 to 205 months), and stable renal allograft function were studied. BMD was quantified by DXA of the hip and spine. QUS of the left heel measured broadband ultrasound attenuation (BUA) and speed of sound (SOS). Stiffness index (SI) was calculated as SI = (0.67 * BUA + 0.28 * SOS) - 420. DXA measurements established the diagnoses of osteopenia and osteoporosis in 49% and 22% of the patients, respectively. Femoral neck BMD and QUS parameters showed good correlation (r = 0.638; P < 0.001). Sensitivities of BUA, SOS, and SI for diagnosing osteoporosis were 100%, and specificities were 73%, 76%, and 78%, respectively. Positive predictive values were 50%, 53%, and 56%, and negative predictive values were 100%. QUS can be recommended for screening patients who do not have osteoporosis. Those suspected of osteopenic bone structure should be examined by additional DXA measurement for quantification before initiation of therapy.