Correlation of Hematocrit and Tacrolimus Level in Liver Transplant Recipients

Abstract

BackgroundTacrolimus is the most widely used immunosuppressive drug after liver transplantation. Whole blood tacrolimus level is used for drug monitoring. Because of strong uptake by erythrocytes (95% to 98%), hematocrit level is an important factor for evaluation whole blood tacrolimus level. There has been no formula to calculate the effect of hematocrit on the whole blood tacrolimus level. The aim of this study is to evaluate the effect of hematocrit on the whole blood tacrolimus level. MethodsTwenty-five patients were included in this study. Blood samples during routine follow-up were used. All patients received tacrolimus for more than 30 days after liver transplantation. Approximately half of the plasma was removed. Blood samples were remixed and remeasured for hematocrit and whole blood tacrolimus levels. Pearson correlation and linear regression were performed to generate a formula for corrected tacrolimus level. ResultsThirteen male and 12 female patients participated in this study. There was a significant positive correlation between hematocrit ratio and tacrolimus ratio (r = 0.765, r2 = 0.585, P < .001). The pattern of linear relationship between hematocrit ratio and tacrolimus ratio is defined by the regression equation, and the formula to correct tacrolimus level at hematocrit 40% is as follows:Correctedtacrolimuslevel=(0.21×tacrolimus)+[0.89×tacrolimus×(40/Hct)] ConclusionHematocrit has a significant effect on tacrolimus level. Better dose adjustment for patients should include the consideration of hematocrit levels. Further studies are required to validate this formula and clinical significance.