Every year, over 1.5 million major surgical procedures take place in the UK NHS, with around 25% of patients experiencing at least one complication. Existing risk-adjustment models for postoperative morbidity, such as the physiological and operative severity score for the enumeration of mortality and morbidity, are outdated and overestimate risk. Another popular model, the American College of Surgeons National Surgical Quality Improvement Programme risk model, is not open source and cannot be applied to other patient populations.

Using data from a prospective multicentre clinical dataset of 118 NHS hospitals (the peri-operative quality improvement programme), we have developed a new risk-adjustment model for postoperative morbidity in patients undergoing colorectal surgery. The study included patients aged 18 years or older, and postoperative morbidity was defined using the postoperative morbidity survey at postoperative day 7.

The final model incorporated 12 variables, such as Rockwood clinical frailty scale, body mass index, and index of multiple deprivation quintile. With a C-statistic of 0.672 (95%CI 0.660–0.684), the model demonstrated good calibration and outperformed existing risk models in widespread use.

This new risk-adjustment model provides valuable case-mix adjustment for a UK population of patients undergoing major colorectal surgery and can be incorporated into continuous monitoring tools like the variable life adjusted display or exponentially-weighted moving average-chart to support high-level monitoring and quality improvement of risk-adjusted outcomes at the population level.

The PQIP-CR risk model was published in Anaesthesia in September 2022 and is available as open access. 

Reference for PQIP-CR model: 

Bedford J, Martin P, Crowe S et al. Development and internal validation of a model for postoperative morbidity in adults undergoing major elective colorectal surgery: the peri‐operative quality improvement programme (PQIP) colorectal risk modelAnaesthesia 2022; 672: 1–12.

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