Correlation of Hematocrit and Tacrolimus Level in Liver Transplant Recipients.
BACKGROUND
Tacrolimus 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.


METHODS
Twenty-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.


RESULTS
Thirteen male and 12 female patients participated in this study. There was a significant positive correlation between hematocrit ratio and tacrolimus ratio (r = 0.765, r(2) = 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: [Formula: see text]


CONCLUSIONS
Hematocrit 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.
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
S
S
Limsrichamrern
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
C
C
Chanapul
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. Electronic address: prawej.mah@mahidol.ac.th.
P
P
Mahawithitwong
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Y
Y
Sirivatanauksorn
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
P
P
Kositamongkol
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
S
S
Asavakarn
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
C
C
Tovikkai
Hepatopancreatobiliary and Transplant Surgery Unit, Division of General Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
W
W
Dumronggittigule
D016903:Drug Monitoring; D004912:Erythrocytes; D005260:Female; D006084:Graft Rejection / Q000517:prevention & control*; D006400:Hematocrit; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood* / Q000627:therapeutic use; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged; D016559:Tacrolimus / Q000097:blood* / Q000627:therapeutic use
D007166:Immunosuppressive Agents; D016559:Tacrolimus