Transition From Dosing Rabbit Antithymocyte Globulin Using Total Body Weight to Adjusted Body Weight Preserves Excellent Outcomes in Obese Renal Transplant Patients.

Abstract

Background: The dosing weight utilized to calculate rabbit antithymocyte globulin (ATG) doses for renal transplantation varies according to transplant center and includes ideal body weight, total body weight (TBW) and adjusted body weight (ABW). However, there is limited literature regarding the optimal dosing weight of ATG in obese patients. This study aims to evaluate graft outcomes associated with the use of ABW as compared to TBW in renal transplant patients. Methods: This is a retrospective single center study of adult obese (BMI ≥ 30) solitary renal transplant patients from 2011 to 2013. All patients received either 4.5 mg/kg ATG for immediate graft function or 6 mg/kg for delayed graft function (DGF) based on respective dosing weight. One year actuarial patient and graft survival, renal function, and prevalence of rejection were reported. Univariate analysis was performed and p<0.05 was consider significant. Results: 41 obese patients underwent renal transplantation: 28 in the TBW group and 13 in the ABW group. One year patient survival (TBW: 96% vs. ABW: 100; p=ns) and graft survival (96% vs. 100; p=ns) was comparable. Baseline demographics were similar between groups, including BMI (34.1±2.6 vs. 34.1±3.0; p=ns), % patients morbidly obese (BMI >35) (32% vs.38; p=ns), and % patients with DGF (14.3% vs. 38.5; p=ns). The TBW group received more ATG per patient as compared to the ABW group (542±102 mg vs. 430 mg±102, p<0.05) or a 21% reduction in total usage. This represents a decreased cost of $1,388 per patient ($10,789± 3,663 vs. 9,401±2,246; p<0.05). No difference in renal function, as determined by estimated glomerular filtration rate, was observed between groups at 3, 6, and 12 months post-transplantation (59±16 ml/min/1.73m2 vs. 57±20; p=ns, 60±19 vs. 56±19; p=ns, 57±22 vs. 51±18; p=ns). Rates of acute rejection were similar between the two groups at 3 and 6 months respectively (21.4% vs. 14.3%; p=ns and 21.4% vs. 15.4%; p=ns). Conclusions: These data suggest that ABW may be safely used to dose ATG while improving value of care through a 21% reduction in ATG usage. Utilizing ABW to dose ATG maintains excellent clinical outcomes with comparable rates of rejection in obese renal transplant patients.