Evaluation of POSSUM and P-POSSUM as predictors of mortality and morbidity in patients undergoing laparotomy at a referral hospital in Nairobi, Kenya

Author Information

Kimani MM1,2, Kiiru JN3, Matu MM3, Chokwe T1,2, Saidi H1,2

  1. University of Nairobi, College of Health Science

  2. Kenyatta National Hospital, Department of surgery

  3. Kenya Medical Research Institute, Centre for Microbiology Research

Corresponding author:

Dr. Moses Kimani, P.O. Box 54270- 00200 Nairobi Kenya, Tel: +254724400193, Email: mwangikimanimoses@gmail.com


Background: The Physiological and Operative Severity Score for enUmeration of Morbidity and Mortality (POSSUM) and its Portsmouth modification (P-POSSUM) were developed for comparative audit in surgical patients. This study evaluated applicability of these systems in estimating mortality and morbidity risks in a cohort of patients undergoing laparotomy at the national referral hospital in Nairobi, Kenya.

Methods: Data of 166 patients undergoing laparotomy was subjected to POSSUM and P-POSSUM scoring systems and analyzed using linear and exponential methods. The discrimination power of POSSUM and P-POSSUM as predictors of surgical outcome was measured using the receiver–operating characteristic (ROC) curve.
Results: The overall observed to expected (O:E) ratio using linear analysis was 0.29:1 (POSSUM) and 0.67:1 (P-POSSUM) while exponential analysis gave an O:E of 0.2:1 (POSSUM) and 0.4:1 (P-POSSUM). The predicted morbidity using POSSUM was 1.09:1 (linear analysis) and 1:1 (exponential analysis). Hosmer–Lemeshow analysis did not show a significant lack of fit with the observed mortality when applied to POSSUM and P-POSSUM. The area under ROC curve was 0.74 (POSSUM) and 0.78 (P-POSSUM).

Conclusion: Our results support the suitability of P-POSSUM and POSSUM scoring systems to stratify morbidity and mortality risk in our study population.


The Annals of African Surgery is the official publication of the Surgical Society of Kenya.


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