Risk indices predicting graft use, graft and patient survival in solid pancreas transplantation: a systematic review

BACKGROUND: Risk indices such as the pancreas donor risk index (PDRI) and pre-procurement pancreas allocation suitability score (P-PASS) are utilised in solid pancreas transplantation however no review has compared all derived and validated indices in this field. We systematically reviewed all risk indices in solid pancreas transplantation to compare their predictive ability for transplant outcomes. METHODS: Medline Plus, Embase and the Cochrane Library were searched for studies deriving and externally validating risk indices in solid pancreas transplantation for the outcomes of pancreas and patient survival and donor pancreas acceptance for transplantation. Results were analysed descriptively due to limited reporting of discrimination and calibration metrics required to assess model performance. RESULTS: From 25 included studies, discrimination and calibration metrics were only reported in 88% and 38% of derivation studies (n = 8) and in 25% and 25% of external validation studies (n = 12) respectively. 21 risk indices were derived with mild to moderate ability to predict risk (C-statistics 0.52–0.78). Donor age, donor body mass index (BMI) and donor gender were the commonest covariates within derived risk indices. Only PDRI and P-PASS were subsequently externally validated, with variable association with post-transplant outcomes. P-PASS was not associated with pancreas graft survival. CONCLUSION: Most of the risk indices derived for use in solid pancreas transplantation were not externally validated (90%). PDRI and P-PASS are the only risk indices externally validated for solid pancreas transplantation, and when validated without reclassification measures, are associated with 1-year pancreas graft survival and donor pancreas acceptance respectively. Future risk indices incorporating recipient and other covariates alongside donor risk factors may have improved predictive ability for solid pancreas transplant outcomes.