Delirium has poor patient outcomes, more so where diagnosis is delayed or missed. Detection tools aid delirium identification but are not always used. We tested the SQiD (Single Question in Delirium) against psychiatrist diagnosis. METHODS: Patients admitted to either of two comprehensive cancer centres, in Sydney, Australia, were prospectively screened. Admissions of 24hrs or less, or for chemo or radiotherapy only, were excluded. The SQiD “Do you feel that [patient’s name] has been more confused lately?” posed to the, relative, carer or friend, was tested against clinical diagnosis by a consultant psychiatrist (PD) based on Diagnostic and Statistic Manual criteria. The primary endpoint was negative predictive value (NPV) of the SQiD versus PD; secondary analysis comprised NPV of SQiD versus NPV of the short Confusion Assessment Method (CAM). RESULTS: Between May 2012 and July 2015, the SQiD plus CAM was applied to 122 patients; 73 had SQiD plus psychiatrist interview. Median age was 68 years, 46% were female with median length of hospital stay of 12 days (interquartile range 5-18 days). Major cancer types were lung (19%), breast (12%) and prostate (11%). 70% of participants had stage 4 cancer. 9% had cerebral metastasis. Agreement was similar between the SQiD (NPV=74%, 95% CI 67-81; kappa=0.32) and CAM (NPV=72%, 95% CI 67-77, kappa=0.32), compared with psychiatrist interview. The CAM identified only a small number of delirious cases but all were true positives. Of the 16 patients with hypoactive delirium, 6 were identified on SQiD, the CAM identified one. The SQiD had higher sensitivity than CAM (44% [95% CI 41-80] vs 26% [10-48]).CONCLUSION: The SQiD, administered by ward clinical staff, was feasible and demonstrated favourable psychometric properties. The SQiD has potential to set a new standard of care as a delirium detection tool for hospitalised cancer patients.