AWOL-S — Age, WORLD backwards, Orientation, iLlness severity and Surgery-specific risk

What this tool is and how to interpret its evidence

AWOL-S is a perioperative risk model derived from the earlier AWOL rule. Its name reflects age, ability to spell WORLD backwards, orientation to place, illness severity represented by ASA physical status, and surgery-specific risk. These inputs are combined into a predicted probability of delirium during the first seven postoperative days. The source programme classified patients at 5% or greater predicted probability as high risk. That threshold supported a local prevention pathway; it should not be treated as a universal diagnostic cutoff. AWOL-S does not identify delirium already present.

Whitlock and colleagues derived the model in 2,091 surgical patients and validated it in 908. Performance was also examined in a later sustained-use cohort. Reported areas under the curve were 0.71, 0.65 and 0.75 across those phases. At the operational 5% threshold, sensitivity was about 75% and specificity about 59-60%. Implementation was associated with modest changes in some medication practices, but observational quality-improvement findings do not prove that the score itself prevents delirium.

AWOL-S should be presented as a related surgery-specific version of AWOL, not another bedside detection family. It combines brief direct assessment with clinical and procedural information and may be embedded in an electronic record. Case mix, surgical coding and local delirium ascertainment affect calibration. High-risk patients still require clinical review and preventive care, while low-risk results cannot rule out postoperative delirium.