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The Reliability and validity of the confusion assessment method (CAM).

I am a registered nurse working in a general medical ward. We have many elderly patients with a range of disease processes. Our patients may also present with existing cognitive dysfunction and/or temporary altered mental states including delirium. These altered mental states may be the result of underlying physiological alterations such as urinary tract infections or cardiac arrhythmias and transient ischaemic attacks, may result as a side effect of drug therapies or may exacerbate confusion in older people with mild cognitive dysfunction following a change in physical environment (Alagiakrishnan, 2015).

Delirium is a common and serious problem affecting older adults, associated with increased mortality, prolonged hospital stays, increased healthcare costs, higher rates of institutionalisation, and decreased functional independence (Adamis et al, 2006). Delirium increases hospital costs by at least $2,500 per patient, resulting in over $6.9 billion (2004 USD) in hospital costs each year (Inouye 2006). Despite its adverse impact, delirium remains poorly recognised in clinical practice. The Confusion Assessment Method is a delirium instrument, first published in 1990 (Inouye, et al) which was created to improve the identification of delirium. Because of its accuracy, brevity, and ease of use by clinical and lay interviewers, the CAM has become the most widely used standardised delirium instrument for clinical and research purposes (Wei, et al 2008).

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, disorganised 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) disorganised 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 (Wei, et al 2008).

Originally developed by literature review and expert consensus, the CAM was validated for content validity against the reference standard ratings of geropsychiatrists, based on the Diagnostic and Statistical Manual for Mental Disorders Third Edition Revised (DSM-IIIR) American Psychiatric Association (1987) criteria. Content validity requires the use of recognised experts in the field to evaluate whether test items actually assess what the tool means to assess (Nestle Nutrition Institute, ND). Several studies included expert assessments (geriatrician, psychiatrist, neuropsychologists and advanced practice nurses) applying DSM-III, DSM-IIIR, DSM-IV, or ICD-10 criteria or a consensus diagnosis (Inouye, et al 1990; Ely, Inouye, et al 2001; Ely, Margolin, et al 2001; Fabbri et al, 2001; Gonzalez, 2004; Laurila, et al 2002; Monette, et al 2002; Pompei, et al, 1995;  Rockwood, et al 1994; Rolfson, et al 1999; Zou, et al 1998).