This article provides a systematic review of the usage of the CAM over the past 16 years. Based on its favorable performance characteristics and ease of use, the CAM has gained widespread usage nationally and internationally. To date, 11 published studies have evaluated the performance characteristics of the CAM compared with reference standard ratings. Based on 7 high quality studies (n=1,071), a combined sensitivity rate has been calculated as 94% (95% CI 91–97%), and combined sensitivity rate of 89% (95% CI 85–94%). Interrater reliability (kappa 0.7–1.0) is generally moderate to high across studies.
Adaptations of the CAM include the CAM-ICU for non-verbal ventilated ICU patients, adaptations for emergency department and nursing home settings (MDS Version 3.0 and the Nursing Home CAM), the Delirium Index for scoring severity, and use of the CAM to identify partial (subsyndromal) forms of delirium. The CAM has been translated into 10 languages where published articles are available. A significant shortcoming of these studies is that not all of the adaptations or translations have been validated against a reference standard to determine their psychometric properties. This will be an important area for future research.
In over 222 application studies, we have documented that the CAM is widely used for both clinical and research applications. While our literature review was comprehensive, some articles may have been missed, particularly those where the term “confusion assessment method” did not appear in the abstract or key search areas or were published in foreign languages.
Based on this review, several recommendations are proposed to optimize the use of the CAM for the identification of delirium. Some training is recommended for optimal use. The Confusion Assessment Method Training Manual is available at http://elderlife.med.yale.edu/pdf/The%20Confusion%20Assessment%20Method.pdf
to facilitate this process. Moreover, the CAM was designed to be scored based on observations made during formal cognitive assessment, such as with brief instruments like the MMSE or SPMSQ. Without such formal assessment (or with extremely brief assessments), the sensitivity of the CAM for delirium detection is compromised. For research purposes, use of the full 9-item CAM instrument is recommended to maximize sensitivity for the detection of delirium.
An important caveat about use of the CAM is worthy of comment. Given its imperfect sensitivity, we do not recommend the CAM as the sole means for identification of delirium in the clinical setting. The use of astute clinical judgment combined with other formal cognitive screening measures is required to avoid missing hypoactive, subtle, or atypical cases of delirium.
This systematic review has helped to uncover gaps in our knowledge base regarding the CAM and to define critical areas where further research is needed. Future work should focus on defining the optimal brief assessment to score the CAM. Based on recent studies (48
), this assessment is likely to require assessment of sustained attention and executive functioning; nonverbal assessments, such as used for the CAM-ICU, are not ideal in verbal patients (24
). In addition, application of combined methods may help to maximize the sensitivity of the CAM for detection of delirium, (e.g., combined assessments (49
), medical record review (50
). Identification of key features that distinguish delirium from dementia at the bedside may help to improve the specificity of the CAM. Future work is needed to validate the use of CAM summary scores or adaptations to measure delirium severity, and to correlate these scores with outcomes. Finally, testing educational efforts to improve the identification of delirium with the CAM features among physicians and nurses are greatly needed.
Despite use of the CAM, the serious and persistent lack of recognition of delirium in clinical settings remains a fundamental problem. Systematic, widespread changes in our approaches to care of older persons will be needed to make substantial impact on the devastating problem of delirium in this population.