The Confusion Assessment Method: a systematic review of current usage.

Delirium is a common and serious problem affecting older adults, associated with increased mortality, prolonged hospital stays, increased healthcare costs, higher rates of institutionalization, and decreased functional independence (1). High-risk settings for delirium include the hospital, intensive care, emergency, post-operative, institutional, and terminal care settings (2). Delirium increases hospital costs by at least $2,500 per patient, resulting in over $6.9 billion (2004 USD) in hospital costs each year (2). Despite its adverse impact, delirium remains poorly recognized in clinical practice. The Confusion Assessment Method is a delirium instrument published in 1990 (3), which was created to improve the identification of delirium. The Confusion Assessment Method (CAM) includes an instrument and diagnostic algorithm for identification of delirium (3). Originally developed by literature review and expert consensus, the CAM was validated against the reference standard ratings of geropsychiatrists based on Diagnostic and Statistical Manual for Mental Disorders Third Edition Revised (DSM-IIIR) (4) criteria. The CAM was designed to allow non-psychiatric clinicians to diagnose delirium quickly and accurately following brief formal cognitive testing. The CAM instrument assesses the presence, severity, and fluctuation of 9 delirium features: acute onset, inattention, disorganized thinking, altered level of consciousness, disorientation, memory impairment, perceptual disturbances, psychomotor agitation or retardation, and altered sleep-wake cycle. The CAM diagnostic algorithm is based on four cardinal features of delirium: 1) acute onset and fluctuating course, 2) inattention, 3) disorganized thinking, and 4) altered level of consciousness. A diagnosis of delirium according to the CAM requires the presence of features 1, 2, and either 3 or 4. The CAM demonstrated sensitivities from 94–100%, specificities from 90–95%, positive predictive accuracy of 91– 94%, negative predictive accuracy of 90–100%, interrater reliability ranging from .81–1.00; and convergent agreement with other mental status tests including the Mini-Mental State Examination (MMSE) (5). The Confusion Assessment Method (CAM) Training Manual was developed to facilitate its appropriate use . Because of its accuracy, brevity, and ease of use by clinical and lay interviewers, the CAM has become the most widely used standardized delirium instrument for clinical and research purposes over the past 16 years. The purpose of this article is to provide a systematic review of all original English language articles utilizing the CAM to synthesize its psychometric properties, adaptations, published translations, and clinical and research applications. Strengths and limitations of the articles have been highlighted. Ultimately, it is hoped that this summary will provide a comprehensive overview of the current utility of the CAM, and recommendations for its appropriate use.