Comparison of P-POSSUM and O-POSSUM in predicting mortality after oesophagogastric resections

• Published in: Postgraduate medical journal 2007-05, Vol.83 (979), p.355-358
• Main Authors: Nagabhushan, J S, Srinath, S, Weir, F, Angerson, W J, Sugden, B A, Morran, C G
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; area under the receiver–operator characteristic curve; AUC; Biological and medical sciences; Clinical Audit; Confidence intervals; Electrocardiography; Epidemiology; Esophageal Neoplasms - mortality; Esophageal Neoplasms - surgery; Esophagectomy - mortality; Female; Gastrectomy - mortality; Gastric cancer; General aspects; Hosmer–Lemeshow; Hospital Mortality; Hospitals; Humans; H–L; Male; Medical prognosis; Medical sciences; Methods; Middle Aged; Morbidity; Mortality; Multivariate analysis; Physiological and Operative Severity Score for the enumeration of Mortality and morbidity; Physiology; POSSUM; Postoperative Complications - mortality; Public health. Hygiene; Public health. Hygiene-occupational medicine; receiver–operator characteristic; Risk Assessment; ROC; ROC Curve; Severity of Illness Index; SMR; standardised mortality ratio; Stomach Neoplasms - mortality; Stomach Neoplasms - surgery; Surgery
• ISSN: 0032-5473; 1469-0756
• DOI: 10.1136/pgmj.2006.053223

Background: P-POSSUM (Physiological and Operative Severity Score for the enumeration of Mortality and morbidity) predicts mortality and morbidity in general surgical patients providing an adjunct to surgical audit. O-POSSUM was designed specifically to predict mortality and morbidity in patients undergoing oesophagogastric surgery. Aim: To compare P-POSSUM and O-POSSUM in predicting surgical mortality in patients undergoing elective oesophagogastric cancer resections. Methods: Elective oesophagogastric cancer resections in a district general hospital from 1990 to 2002 were scored by P-POSSUM and O-POSSUM methods. Observed mortality rates were compared to predicted mortality rates in six risk groups for each model using the Hosmer–Lemeshow goodness-of-fit test. The power to discriminate between patients who died and those who survived was assessed using the area under the receiver–operator characteristic (ROC) curve. Results: 313 patients underwent oesophagogastric resections. 32 died within 30 days (10.2%). P-POSSUM predicted 36 deaths (χ2 = 15.19, df = 6, p = 0.019, Hosmer–Lemeshow goodness-of-fit test), giving a standardised mortality ratio (SMR) of 0.89. O-POSSUM predicted 49 deaths (χ2 = 16.51, df = 6, p = 0.011), giving an SMR of 0.65. The area under the ROC curve was 0.68 (95% confidence interval 0.59 to 0.76) for P-POSSUM and 0.61 (95% confidence interval 0.50 to 0.72) for O-POSSUM. Conclusion: Neither model accurately predicted the risk of postoperative death. P-POSSUM provided a better fit to observed results than O-POSSUM, which overpredicted total mortality. P-POSSUM also had superior discriminatory power.