Do risk adjustment calculations used by governmental agencies adequately assess risk for infection after colon surgery?

BACKGROUND:Surgical site infections (SSIs) following colon surgery are associated with clinical and financial consequences. The Centers for Medicare and Medicaid Services (CMS) and the New York State Department of Health (NYSDOH) use risk adjustment variables to determine quality measure scores. METHODS:Among patients in a large public system, surgical risk variables were compared between patients with and without SSIs. Propensity score matching, using CMS and NYSDOH risk variables, created control groups. Receiver Operating Characteristics (ROC) curves were created using current and augmented risk adjustment variables. RESULTS:When matched using CMS risk variables, more patients with SSIs had contaminated/dirty wounds, longer duration of surgery, and emergency surgery. The addition of these variables significantly improved the CMS ROC curve. When matching NYSDOH variables, more SSI patients were male, had contaminated/dirty wounds, and tended to be younger. The addition of these variables to the current NYSDOH adjustment criteria did not significantly improve the ROC curve. DISCUSSION:The CMS adjustment criteria for colon SSIs do not adequately account for complicated surgeries. The inclusion of additional variables significantly improved the performance of CMS risk adjustment. CONCLUSIONS:Until more robust risk adjustment criteria are developed, the reporting of SSIs following colon surgery as a quality measure should be suspended.