Case-mix adjustment in audit of length of hospital stay in patients operated on for cancer of the head and neck.

Patients treated surgically for squamous cell carcinoma (SCC) of the head and neck form a heterogeneous group, and it is difficult to take this variation into account when measuring the quality of care. We have tested the feasibility of mathematical models that allow for the adjustment for case mix when auditing the length of hospital stay as a proxy indicator of the quality of care. We completed a case-note audit of 733 surgical episodes of care for SCC of the head and neck in five cancer networks, and used logistic regression and decision tree analysis to adjust for case mix using pertinent preoperative variables. Risk adjustment models of length of stay included age, alcohol, T classification, performance status, tracheostomy, high-risk status, and complexity of operation. The risk-adjusted length of stay differed significantly between the cancer networks studied (p<0.001). The models performed acceptably for the purpose of audit when this was under 15 days. Length of stay is a measurable outcome that can be used as a benchmark of surgical care. Audits of this after operations for cancer of the head and neck, if reported in national clinical audits, should take case mix into account.