Comparison of the risk prediction systems POSSUM and P-POSSUM with the Surgical Risk Scale: A prospective cohort study of 721 patients

• Two systems of surgical risk scoring (POSSUM vs Surgical Risk Scale) are compared.
• The Surgical Risk Scale is obtained from preoperative data and is easy to complete.
• The Surgical Risk Scale is useful in mortality prediction, even in low-risk patients.
• The article validates the Surgical Risk Scale outside UK Hospitals.
• POSSUM overestimates expected morbidity in developed countries.

IntroductionThe outcomes of surgery are subject to variability and difficult to be accurately predicted. Different score systems have been developed to estimating the risk of undergoing a surgical procedure.The aim of this study was to assess the predictive ability of POSSUM and P-POSSUM scoring systems, compared to the Surgical Risk Scale (SRS), in Spanish patients undergoing general surgery.Patients and MethodsIn this prospective observational study, 721 consecutive patients needing a surgical procedure were included. Observed morbidity and mortality after surgery were compared to the expected ones obtained by applying POSSUM, P-POSSUM and SRS.ResultsMean age was 59.2 years (standard deviation (SD): 17.4 years), 43.5% were women. 616 (85.5%) patients underwent elective general surgery and 105 (14.5%) emergency surgery. The 30-day morbidity was 15.4%. The reintervention rate was 2.1% and mortality was 2.1%.The discrimination ability was excellent in predicting mortality. The Area Under the Curve (AUC) values were: POSSUM: AUC = 0.97, C.I.95%: 0.948–0.992, p < 0.0001; P-POSSUM: AUC = 0.966, C.I.95%: 0.941–0.991, p < 0.0001; SRS: AUC = 0.91, C.I.95%:0.853–0.967, p < 0.0001. POSSUM was also discriminative in the prediction of morbidity (AUC = 0.772, C.I.95%: 0.719–0.826, p < 0.0001).POSSUM predicted morbidity and mortality were higher than the observed ones (p = 0.01 and p = 0.04). Predicted and observed mortality were very similar for P-POSSUM (p = 0.93) and SRS (p = 0.37).ConclusionsExpected morbidity and mortality determined by POSSUM score showed values significantly above the observed ones. P-POSSUM and SRS systems were effective in predicting mortality. The SRS application is simple and may contribute to appropriate medical decision making.