POSSUM and P-POSSUM

The POSSUM included 12 physiology scores (PS) and six operative severity scores (OS). Each variable had a 4-level classification, with increasing scores (1, 2, 4, 8). In the absence of data, the assigned score was 1.4,8 Specific scoring rules are shown in Table 1. The preoperative physiological indicators used the data closest to the time of surgery. The elective surgical indicators were collected within 24 h before the operation, and the emergency surgical indicators were collected within 6 h before. The intraoperative indicators were based on the surgical and anesthesia records. Data were entered into the clinical database by another group of non-medical professionals. By substituting PS and OS into regression equations, the POSSUM scoring system predicted the postoperative complication rate (R1) and mortality rate (R2), and the P-POSSUM predicted the postoperative mortality rate (R). The calculation formula4,5 was as follows:

Parameters Used to Calculate the POSSUM Score

Abbreviation: POSSUM, physiological and operative severity score for the enumeration of mortality and morbidity.

By substituting the PS and OS of each patient into the different regression equations above, we obtained the complication risk coefficient and mortality risk coefficient predicted by POSSUM or P-POSSUM, and then converted the risk coefficient into a percentage. Using the predicted complication rate and mortality rate of each patient, we were able to derive the overall predicted complication rate and mortality rate of all 274 patients.