Date Published: January 27, 2017
Publisher: Public Library of Science
Author(s): Ricardo Salinas Saldaña, Harald Schrem, Marc Barthold, Alexander Kaltenborn, Tatsuo Kanda.
Model of end-stage liver disease (MELD)-score and diverse variants are widely used for prognosis on liver transplant waiting-lists.
818 consecutive patients on the liver transplant waiting-list included to calculate the MELD, MESO Index, MELD-Na, UKELD, iMELD, refitMELD, refitMELD-Na, upMELD and PELD-scores. Prognostic abilities for 90-day mortality were investigated applying Receiver-operating-characteristic-curve analysis. Independent risk factors for 90-day mortality were identified with multivariable binary logistic regression modelling. Methodological quality of the underlying development studies was assessed with a systematic assessment tool.
74 patients (9%) died on the liver transplant waiting list within 90 days after listing. All but one scores, refitMELD-Na, had acceptable prognostic performance with areas under the ROC-curves (AUROCs)>0.700. The iMELD performed best (AUROC = 0.798). In pediatric cases, the PELD-score just failed to reach the acceptable threshold with an AUROC = 0.699. All scores reached a mean quality score of 72.3%. Highest quality scores could be achieved by the UKELD and PELD-scores. Studies specifically lack statistical validity and model evaluation.
Inferior quality assessment of prognostic models does not necessarily imply inferior prognostic abilities. The iMELD might be a more reliable tool representing urgency of transplantation than the MELD-score. PELD-score is assumedly not accurate enough to allow graft allocation decision in pediatric liver transplantation.
The Model of End-Stage Liver Disease (MELD) Score has originally been developed as a prognostic model to estimate 90-day mortality for patients who require a transjugular intrahepatic portosystemic shunt procedure .The original MELD score is based on three laboratory values including serum creatinine, serum bilirubin and the International Normalized Ratio (INR) and the cause of cirrhosis . In 2001, Kamath et al. evaluated the Model of End-Stage Liver Disease (MELD) Score as a prognostic model in patient groups with a broader range of disease severity and etiology and suggested its application in donor liver allocation policies for liver transplantation . Subsequently, Wiesner et al. assessed the capability of the MELD Score without including the cause of cirrhosis into the MELD Score formula to correctly rank potential liver recipients according to their severity of liver disease and mortality risk on the OPTN liver waiting list in the US. They were able to show that the MELD score can accurately predict 90-day mortality among patients with chronic liver disease on the liver waiting list and can be applied for allocation of donor livers (see Table 1) . Today, the MELD Score is applied in liver allocation policies in several countries world-wide, including the US and Germany [4, 5]. Since its introduction in German allocation policies, waiting list mortality has decreased from approximately 20% to 10% while post-transplant patient survival has declined significantly leading to 1-year survival rates that are up to 20% lower as compared to the United States and the United Kingdom [6–9]. It is astonishing that the MELD score has been introduced into liver allocation policies in Germany in December 2006 without prior validation of the prognostic ability of this prognostic model in German waiting list patients violating one of the essential quality assessment criteria for prognostic models as proposed by Jacob et al. in 2005 .
This is the first systematic evaluation of the quality and external validity of several prognostic models for 90-day mortality on the waiting list for liver transplantation. The quality of these models was assessed by three different investigators using the quality assessment tool proposed by Jacob et al. .The prognostic abilities of these models were assessed with an independent large data set from a single institution.