Applicability of the medication level variability index (MLVI) in adult hepatic transplantation and association with graft rejection rates

Introduction: Calculation of the Tacrolimus variation index by using the MLVI (Medication Level Variability Index) is set in pediatric liver transplant patients, and it is useful in controlling treatment adherence by associating MLVI values > 2.5 to acute graft liver rejection. Purpose: To verify the association between MLVI values and rejection in adult liver transplant patients. Methods: A retrospective cohort study including liver transplant patients over 18 years of age from December 2012 to December 2017 using orally tacrolimus. For MLVI calculation, tacrolimus serum level outpatient samples were used after 1 year of transplantation. Results: A total of 125 patients were transplanted, of which 86 met criteria for inclusion in the study. The most frequent reason for transplantation was C virus infection (55.8%, n = 48). Rejection was identified in 18.6% of patients (n = 16). The mean MLVI among rejection and nonrejection patients was 2.5 and 2.1 respectively (RR = 0.95, CI: 0.4-2.1, p = 0.57). The frequency of non-immunological complications was 56.2% (n = 9) in patients with rejection versus 62.8% (n = 44) in patients without rejection, most of them with recurrence of virus C (56,8%, n = 25). Conclusion: Although the mean value of MLVI was higher in patients with rejection, our data showed no statistical difference between both groups, which differs from previous studies in pediatric patients. A higher number of nonimmune complications were observed in patients without rejection. The findings suggest that new MLVI cutoffs should be explored in the adult population.