The ultimate goal for an allograft is a balanced immunosuppression to provide the longest graft survival with minimal side effects. In this retrospective study, we correlate the immunosuppresion level as determined using the Cylex assay (Immu know, Columbia, MD) with clinical events. Demographic data such as age at the time of transplant, gender, ethnicity, time posttransplantation, tacrolimus level, and induction therapy were correlated with Cylex levels. Cylex from children with an infection or acute rejection were compared to those from stable patients. All children received induction with basiliximab or thymoglobulin followed by a standard regimen with tacrolimus, steroids, and mycophenolate mofetil. Fifty-nine Cylex results were obtained in 44 pediatric renal transplant recipients. Cylex values ranged from 20 ng/mL to 728 ng/mL. We did not find significant correlation between any of the demographic characteristics studied (tacrolimus level, induction therapy, acute rejection, and Cylex levels). Fifteen patients had severe infections requiring hospitalization: 11 of 15 (73%) had Cylex<130 ng/mL; these levels differed significantly from those obtained in patients without infections. We concluded that clinical utility of Cylex is limited in children with kidney transplants because it did noes correlate with the prescribed dosage of medications or with rejection. However, low Cylex levels were highly correlated with serious infections.
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