Measurement of skeletal status after renal transplantation by quantitativeultrasound

Background: Osteoporosis remains a major problem following kidney transplan tation. Radiographic measures of bone mass are of limited predictive value after transplantation and are complicated by preexisting renal osteopathy. Quantitative ultrasound (QUS) is a new and non-invasive method to assess sk eletal status, however, no data exist on ultrasonic bone parameter after ki dney transplantation. We evaluated the potential use of this novel method i n renal allograft recipients and studied the accuracy compared to normal co ntrols. Method: Thirty patients (NTP, age 47.5 +/- 13.0 years) were studied 4.8 +/- 3.2 years after transplantation. Twenty-five healthy control perso ns (CON) were matched for age and sex. The left and right os calcis were st udied by QUS and speed of sound (SOS) and broadband ultrasound attenuation (BUA) were measured. Bone stiffness (BS) was calculated from these paramete rs and corrected for age (CBS). Differences between right and left os calci s were compared to CON to assess the side variability, Results: Mean +/- SD BS was 75 +/- 22% compared to young adults, age-corrected CBS was decrease d in NTP with 86 +/- 25% of normal, indicating a two-fold increased risk of fracture. SOS was 1525 +/- 47.7 m/s, BUA 105 +/- 22 dB/MHz. Mean differenc e between right and left os calcis was significantly higher in NTP than in CON (7.2 +/- 7.1% vs. 2.1 +/- 2.1%, p < 0.01). Limits of agreement of the m easurements (MW of differences +/- 2 SD) according to a Bland-Altmann-type statistic were -16.9% and 20,7%. There was no correlation between CBS and a ge, cumulative steroid dose, parathyroid hormone concentrations or time aft er transplantation. Conclusion: Our data show altered bone structure expres sed by low bone stiffness values measured by quantitative ultrasound in kid ney transplant patients. However, because of relatively high inter-feet var iance of QUS results we suggest measurement of both ossa calcis to minimize measurement error after transplantation.