Impact of an Institutional Change in Prothrombin Time Methodology on INR and MELD Scores in Liver Transplant Evaluations.

Abstract

Allocation of liver grafts based on the model for end-stage liver disease (MELD) has been questioned because the prothrombin time (PT) measurement in cirrhosis patients changes with different commercially available thromboplastin reagents due to variations in the international sensitivity index (ISI). Our hospital laboratory electively changed the thromboplastin used in the PT/INR from PT-HS (ISI of 1.464) to Recombiplastin (ISI of 0.870). Theoretically, this change may yield lower INR and MELD scores in cirrhosis patients at our institution and thus impact access to organs. 27 patients listed for liver transplant prior to change in thromboplastin (Cohort A) were compared to 36 patients listed after the change (Cohort B). Patients in Cohort A had a mean INR of 1.41 and mean MELD of 13.9 compared to Cohort B with a mean INR of 1.39 and mean MELD of 13.8. Student's t-tests showed no statistically significant difference in INR (p = 0.799) or MELD (p = 0.955) between cohorts. We expected overall INR and MELD scores to decrease following the change to a thromboplastin with a lower ISI. On the contrary, we found no evidence of a major trend in these values supporting the relative robustness of the MELD.