There are varied Thymoglobulin® (Thymo) induction regimens accepted among transplant programs. Our center uses five doses of Thymo at 1.25mg/kg, yielding a total goal of 6.25mg/kg. Doses are decreased by 50% for absolute lymphocyte count (ALC) < 0.2 and held for ALC = 0. The primary objective was to evaluate the effect of adjusting Thymo based on ALC on rejection and infection rates.

Methods: A retrospective chart review of 123 adult kidney transplant alone recipients from January through December 2013 was conducted. Outcomes were biopsy proven acute cellular rejection (AR) and infection.

Results: Two patients were excluded due to enrollment in an induction study. The final data set included 121 patients: 100 primary transplant and 21 re-transplants. Demographics included: 83% Caucasian, 64% male and 52% deceased donor. No graft loss occurred secondary to rejection. The overall rejection rate was 16.5%.

Patients were separated into four categories based on total Thymo dosing during the induction period: ≤ 4, 4-5.4, 5.5-7 and > 7mg/kg. These groups were chosen based on a protocol goal of 6.25mg/kg, +/- 0.75 mg/kg.

There were no rejections seen in the <4mg/kg group. In the group receiving 4-5.4 mg/kg of Thymo, ten patients (27.8%) were treated for AR. Seven of the ten rejections developed 2-4 weeks post transplant. In this group of seven rejections: nine doses were adjusted for ALC< 0.2 (6 patients). Two more rejections occurred 1-3 months post transplant with both patients having one dose adjusted for ALC.

Seven patients (12.3%) were treated for AR in the 5.5-7 mg/kg group. Over half of the rejections occurred >3 months post transplant. Two rejections occurred 2-4 weeks post transplant with one patient having two doses of Thymo adjusted for ALC.

The > 7mg/kg Thymo group had three patients (12.5%) treated for AR. No rejections occurred within the first month post transplant. The main reasons these patients received a higher dose of Thymo was due to slow graft function and sub therapeutic calcineurin inhibitor levels.

Overall fungal and viral infection rate was 12.3%. The fungal and viral infection rate did not differ in the 4-5.4mg/kg group or 5.5-7mg/kg group, see table.

Conclusion: Compared to our goal, Thymo dose adjustments based on ALC often led to decreased Thymo use and increased rejection rates without the benefit of minimizing infection.

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