The Confusion Assessment Method (CAM)

Issue #13 of General Assessment Series

WHY: Delirium is a serious, potentially preventable, neuropsychiatric disorder occurring in association with other underlying medical conditions (DSM V, 2013). Delirium is under-recognized and underdiagnosed making accurate prevalence and incidence difficult to gauge. A point-prevalence study conducted in 2016 examined over 1800 older adults, with a mean age of 82 +/- 7.5 years, in hospital settings and found one in five of these individuals had delirium (Bellelli et al., 2016). Other sources report that delirium can affect up to 50% of individuals over the age of 65 years in hospitals (Inouye, Westendorp, & Saczynski, 2014). Delirium often occurs after an acute illness or hospitalization and is associated with loss of physical function, increased morbidity and mortality, nursing home placement, and high health care costs (Oh, Fong, Hshieh, & Inouye, 2017). Predisposing risk factors for delirium include older age, dementia, severe illness, multiple co-morbidities, alcoholism, vision impairment, hearing impairment, and a history of delirium. Precipitating risk factors include acute illness, surgery, pain, dehydration, sepsis, electrolyte disturbance, urinary retention, fecal impaction, and exposure to high risk medications. Delirium is often unrecognized and undocumented by clinicians. Rates of unrecognized delirium, which is defined as the diagnosis of delirium after being unrecognized by a primary physician or nurse is estimated to be about 60% of all cases (Oh, Fong, Hshieh, & Inouye, 2017). This high rate of unrecognized delirium underscores the need for screening to detect delirium early. Early recognition and treatment can improve outcomes. A key issue in recognizing delirium is understanding the older adult’s baseline and quickly identifying changes, which in the case of delirium can occur within hours. Therefore, older adults should be assessed frequently using a standardized tool to facilitate prompt identification and management of delirium and underlying etiology.

BEST TOOL: The Confusion Assessment Method (CAM) is a standardized evidence-based tool that enables non-psychiatrically trained clinicians to identify and recognize delirium quickly and accurately in both clinical and research settings. The CAM includes four features found to have the greatest ability to distinguish delirium from other types of cognitive impairment. There is also a CAM-ICU version for use with non-verbal mechanically ventilated patients (See Try This:® CAM-ICU). The CAM-S is a companion tool to the CAM that can be used to assess the severity of delirium (Inouye, Kosar, Tommet et al., 2014).

VALIDITY AND RELIABILITY: Both the CAM and the CAM–ICU have demonstrated sensitivity of 94-100%, specificity of 90-95% and high inter-rater reliability (Oh, Fong, Hshieh, & Inouye, 2017). Several studies have been done to validate clinical usefulness.

STRENGTHS AND LIMITATIONS: The CAM may be incorporated into routine assessment and has been translated into several languages. The CAM was designed and validated to be scored based on observations made during brief but formal cognitive testing, such as brief mental status evaluations. Training to administer and score the tool is necessary to obtain valid results. The screening tool alerts clinicians to the presence of possible delirium. A positive screening test result should lead to further investigation.

FOLLOW-UP:  The presence of delirium warrants prompt intervention to identify and treat underlying causes and provide supportive care. Vigilant efforts need to continue across the healthcare continuum to preserve and restore baseline mental status.


The Hospital Elder Life Program (HELP), Yale University School of Medicine. Home Page:

Bellelli, G., Morandi, A., Di Santo, S.G., Mazzone, A., Cherubini, A., Mossello, E., ... & Musicco, M. (2016). “Delirium Day”: A nationwide point prevalence study of delirium in older hospitalized patients using an easy standardized diagnostic tool. BMC Medicine, 14(1), 106.

Cole, M.G., Ciampi, A., Belzile, E., & Zhong, L. (2009). Persistent delirium in older hospital patients: A systematic review of frequency and prognosis. Age and Ageing, 38(1), 19-26.

Diagnostic and Statistical Manual of Mental Disorders, 5th Ed. Washington, DC: American Psychiatric Association; 2013. Inouye, S.K. (2006). Delirium in older persons. NEJM, 354, 1157-1165.

Inouye, S.K., Kosar, C.M., Tommet, D., Schmitt, E.M., Puelle, M.R., Saczynski, J.S., ... & Jones, R.N. (2014). The CAM-S: development and validation of a new scoring system for delirium severity in 2 cohorts. Annals of Internal Medicine, 160(8), 526-533.

Inouye, S., van Dyck, C., Alessi, C., Balkin, S., Siegal, A. & Horwitz, R. (1990). Clarifying confusion: The confusion assessment method. Annals of Internal Medicine, 113(12), 941-948.

Maldonado, J.R. (2008). Delirium in the acute care setting: Characteristics, diagnosis and treatment. Critical Care Clinics, 24(4), 657-722.

Oh, E.S., Fong, T.G., Hshieh, T.T., & Inouye, S K. (2017). Delirium in older persons: Advances in diagnosis and treatment. JAMA, 318(12), 1161-1174.

Rice, K.L., Bennett, M., Gomez, M., Theall, K.P., Knight, M., & Foreman, M.D. (2011, Nov/Dec). Nurses’ recognition of delirium in the hospitalized older adult. Clinical Nurse Specialist, 25(6), 299-311.

Tullmann, D.F., Fletcher, K., & Foreman, M.D.  (2012). Delirium. In M. Boltz, E. Capezuti, T.T. Fulmer, & D. Zwicker (Eds.), A. O’Meara (Managing Ed.), Evidence-based geriatric nursing protocols for best practice (4th ed., pp 186-199). NY: Springer Publishing Company, LLC. 

Vasilevskis, E.E., Morandi, A., Boehm, L., Pandharipande, P.P., Girard, T.D., Jackson, J.C., Thompson, J.L., Shintani, A., Gordon, S.M., Pun, B.T., & Ely, E.W. (2011). Delirium and sedation recognition using validated instruments: Reliability of bedside intensive care unit nursing assessments from 2007 to 2010. JAGS, 59 (Supplement s2), S249-S255. 

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