International Normalized Ratio of Prothrombin Time in the Model for End-stage Liver Disease Score: An Unreliable Measure

The current basis for deceased donor liver allocation is the Model for End-stage Liver Disease (MELD) score, which is an objective means of predicting 90-day patient survival. Although the MELD system is a vast improvement over the prior allocation scheme, published studies have refuted the United Network for Organ Sharing statement that "the MELD and PELD [Pediatric End-stage Liver Disease] formulas are simple, objective and verifiable and yield consistent results whenever the score is calculated." In particular, wide inter-laboratory variation exists in the most heavily weighted MELD determinant, the international normalized ratio (INR). Whether this variation impacts the equitable distribution of deceased donor livers is unclear. However, the current technique for measuring the INR has the potential to detract from the expressed purpose of MELD-based allocation, which is to prioritize liver transplant candidates across the country with parity, using an objective scoring system.