Screening for delirium with the Confusion Assessment Method (CAM)

Contributed by Sharon K. Inouye, M.D., MPH; Richard N. Jones, ScD; Edward R. Marcantonio, M.D., SM

Overview. The Confusion Assessment Method (CAM) was published in 19901 in a highly cited article in the Annals of Internal Medicine as the first brief, standardized method for identification of delirium at the bedside. It provided a standardized rating for key features of delirium, which was intended for flexible use with any cognitive test. Since its publication, the CAM has emerged as the most widely used tool for recognition of delirium worldwide. It is available as a long form with 10 items that have formed a reference standard for identification of delirium, and a short form of 4 items that serves as a diagnostic algorithm (acute onset/fluctuating course; inattention; and either disorganized thinking or altered level of consciousness). A systematic review from 2008 found in 7 validation studies involving >1000 patients, CAM was highly sensitive (94%) and specific (89%).2 In a later study in 2013, involving 22 validation studies, the CAM had a sensitivity of 82% (95% confidence interval, CI, 69-91%) and a specificity of 99% (95% CI 87-100%).3 On the Web of Science (as of 6/24/2020), the original CAM article has >2570 citations with >940 citations in the past 5 years alone. Importantly, the CAM facilitates the identification of patients who fulfill DSM-5 criteria for delirium.

Adaptations. The CAM has been translated into over 20 languages to date, with expert back-translation approaches. In addition, the CAM has been adapted for use across a variety of clinical settings with brief, standardized assessments to score the diagnostic algorithm (See https://deliriumnetwork.org/ for more information on the CAM and related instruments). The CAM-ICU is a widely used adaptation which is highly effective for identification of delirium in non-verbal patients in the ICU, using a short assessment battery.4 The CAM-ICU has been widely validated in multiple studies, and has over 20 translations. The 3D-CAM provides a <3-minute standardized assessment for scoring the CAM algorithm in medical patients with high sensitivity and specificity, with 10 translations.5 Similar standardized brief assessments have been developed to score the CAM algorithm in the emergency department (B-CAM)6 and nursing home (NH-CAM).7 The CAM algorithm has been integrated into the US Nursing home Resident Assessment Instrument / Minimum Data Set (MDS) version 3.0.8 A family-rated version of the CAM (the FAM-CAM) has been developed and validated to enhance caregiver recognition of delirium.9  A CAM-severity scoring system (CAM-S) has been shown to correlate directly with clinical outcomes.10 The CAM has been incorporated into many electronic medical record systems worldwide.

The future of the CAM: The ultra-brief CAM (UB-CAM).  Given its broad versatility, adaptations, and widespread use across clinical settings, along with its important alignment with DSM-5 criteria, the CAM has become the standard for delirium identification worldwide. The major limitation with the CAM to date has been the lack of a quick, standardized approach for rating the diagnostic algorithm in verbal patients across settings. Now, an ultra-brief CAM (UB-CAM) will be unveiled soon (1 minute for administration). Please stay tuned!

References:

  1. Inouye SK, Van Dyck CH, Alessi CA, Balkin S, Siegal AP, Horwitz RI. Clarifying confusion: The Confusion Assessment Method.  A new method for detection of delirium. Ann Intern Med. 1990; 113: 941 948.
  2. Wei LA, Fearing MA, Sternberg E, Inouye SK. The Confusion Assessment Method (CAM):  A systematic review of current usage.  J Am Geriatr Soc. 2008;56:823-830.
  3. Shi Q, Warren L, Saposnik G, Macdermid JC. Confusion assessment method: a systematic review and meta-analysis of diagnostic accuracy. Neuropsychiatr Dis Treat. 2013;9:1359–70.
  4. Ely EW, Margolin R, May FJ, Truman B, Wheeler A, Dittus R, Speroff T, Gautam S, Bernard GR, Inouye SK. Evaluation of delirium in critically ill patients:  Validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU).  Crit Care Med. 2001; 29:1370-1379
  5. Marcantonio ER, Ngo L, O’Connor MA, Jones RN, Crane PK, Metzger ED, Inouye SK. 3D-CAM: Validation of a 3-Minute Diagnostic Interview for CAM-defined Delirium. Ann Int Med. 2014;161:554-61.
  6. Han, J., Wilson, A., Vasilevskis, E., Shintani, A., Schnelle, J., Dittus, R., Graves, A., Storrow, A., Shuster, J., Ely, E.W. Diagnosing Delirium in Older Emergency Department Patients: Validity and Reliability of the Delirium Triage Screen and the Brief Confusion Assessment Method. Ann Emerg Med. 2013;62:457-465
  7. Dosa D, Intrator O, McNicoll L, Cang Y, Teno J. Preliminary Derivation of a Nursing Home Confusion Assessment Method Based on Data From the Minimum Data Set. J Am Geriatr Soc. 2007;55:1099-105
  8. Centers for Medicare & Medicaid Services. MDS 3.0 RAI Manual. 2019.
  9. Steis MR, Evans L, Hirschman KB, Hanlon A, Fick DM, Flanagan N, Inouye SK. Screening for Delirium via Family Caregivers: Convergent Validity of the Family Confusion Assessment Method (FAM-CAM) and Interviewer-Rated CAM. J Am Geriatr Soc. 2012; 60:2121-26
  10. Inouye SK, Kosar CM, Tommet D, Schmitt EM, Puelle MR, Saczynski JS, Marcantonio ER, Jones RN. The CAM-S: Development and Validation of a New Scoring System for Delirium Severity in 2 Cohorts. Ann Intern Med. 2014; 160: 526-533.
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