Optimized surveillance frequency for low bone mineral density (BMD) screening using dual energy X-ray absorptiometry (DXA) in patients after lung transplant

Abstract

BackgroundApproximately 2700 lung transplants are performed annually in the United States. These patients are at increased risk of developing low bone mineral density (osteopenia/osteoporosis) and subsequent osteoporosis-related fractures. Dual energy x-ray absorptiometry (DXA) is the most common method used for screening for low BMD, however, the optimal surveillance frequency for low BMD using DXA is unknown. MethodsWe evaluated the change in femoral neck, total femur, L1, L2, L3 and L4 BMD after lung transplant in a retrospective cohort of 259 patients (69.9% male) who were followed with serial DXA scans for a median of 725 (interquartile range (IQR) (361-1116)) days after transplant. Generalized linear mixed effects models allowing for random intercepts and random slopes adjusting for sex, time, time-squared, baseline osteopenia/osteoporosis, active rejection, and their interaction terms were used to model the rate of change of BMD at each site. The final multivariable models for the femoral neck, L1, and L4 BMD measurements had random slopes and intercepts, and the models for the total hip, L2, and L3 measurements had random slopes. Results65% of the patients undergoing lung transplants had osteopenia or osteoporosis before transplant. Men exhibited higher baseline BMD levels compared to women at all sites (P<0.001 for all). After transplant, the greatest rate of BMD decrease was at the femoral neck. Although patients with low BMD (osteopenia/osteoporosis) had significantly lower baseline BMDs (P<0.001 for all), they experienced a slower rate of BMD decrease at all sites compared to patients with normal BMD at baseline (P<0.001 for all). All patients received corticosteroids. 25% of patients had a history of active rejection. Patients with low BMD at baseline had significantly higher odds of receiving bisphosphonate therapy (odds ratio (OR) = 3.95, 95% CI (1.44, 13.51), P=0.003). We estimated that a significant change in the femoral neck BMD would be expected to occur within 409 days (95% CI (131, 708)) and again at 867 days (95% CI (551, 1216)) after lung transplant. ConclusionsOn average, patients undergoing lung transplant should be screened annually with DXA for the first two years after transplant, consistent with the current International Society for Heart and Lung Transplantation (ISHLT) guidelines.