Qiyun Shi,1,2 Laura Warren,3 Gustavo Saposnik,2 Joy C MacDermid1 1Health and Rehabilitation Sciences, Western University, London, Ontario, Canada; 2Stroke Outcomes Research Center, Department of Medicine, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; 3Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada Background: Delirium is common in the early stages of hospitalization for a variety of acute and chronic diseases. Objectives: To evaluate the diagnostic accuracy of two delirium screening tools, the Confusion Assessment Method (CAM) and the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Methods: We searched MEDLINE, EMBASE, and PsychInfo for relevant articles published in English up to March 2013. We compared two screening tools to Diagnostic and Statistical Manual of Mental Disorders IV criteria. Two reviewers independently assessed studies to determine their eligibility, validity, and quality. Sensitivity and specificity were calculated using a bivariate model. Results: Twenty-two studies (n = 2,442 patients) met the inclusion criteria. All studies demonstrated that these two scales can be administered within ten minutes, by trained clinical or research staff. The pooled sensitivities and specificity for CAM were 82% (95% confidence interval [CI]: 69%–91%) and 99% (95% CI: 87%–100%), and 81% (95% CI: 57%–93%) and 98% (95% CI: 86%–100%) for CAM-ICU, respectively. Conclusion: Both CAM and CAM-ICU are validated instruments for the diagnosis of delirium in a variety of medical settings. However, CAM and CAM-ICU both present higher specificity than sensitivity. Therefore, the use of these tools should not replace clinical judgment. Keywords: confusion assessment method, diagnostic accuracy, delirium, systematic review, meta-analysis