Correlation between viral load of cytomegalovirus and tacrolimus and sirolimus levels in transplanted pediatric patients

Introduction Survival of transplant patients and grafts depends largely on the use of immunosuppressive drugs. However, a balance remains to be established among immunosuppression, transplant rejection and cytomegalovirus (CMV) infection, which results in a high rate of morbidity and mortality. The aim of this study was to define a better strategy for monitoring transplanted patients based on the analysis of the blood concentration of sirolimus and tacrolimus and the burden of CMV. Methods Fifty five post-transplant (kidney and liver) pediatric patients, nine treated with sirolimus and 46 treated with tacrolimus, were included. A total of 541 measurements were obtained. In each measurement the concentration of immunosuppressant in whole blood and CMV viral load in plasma and whole blood was quantified by real-time PCR. Pearson correlation coefficient (r) was estimated. Results Values of r ≤0.0747 were found for the relationship between dose and concentration of immunosuppressant; r = 0.9406 for the relationship between viral load in whole blood and plasma, and r ≤0.4616 for the relationship between concentration of immunosuppressant and viral load. Conclusions These data support that the doses of immunosuppressive drugs do not correlate with the levels of the same in whole blood. Therefore, systemic levels of immunosuppressant should be constantly monitored together with CMV load. Meanwhile, a high correlation between viral load measured in whole blood and plasma was found.