Confusion Assessment Method

The Confusion Assessment Method (CAM) is a diagnostic tool developed to allow non-psychiatric physicians and nurses to identify delirium in the healthcare setting.[1][2][3] It was designed to be brief (less than 5 minutes to perform) and based on criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM).[2] It includes four diagnostic criteria from the third edition of DSM (DSM-III-R): acute onset and fluctuating course, inattention, disorganized thinking, and altered level of consciousness.[1][2] The CAM requires that a short cognitive test and interview is performed before it is completed.[4]

The CAM has gained widespread use since its development in 1990.[1][3][5][6] The tool was constructed through literature review and expert opinion and validated by psychiatrists using the DSM-III-R criteria for delirium.[2] It has been translated into more than 20 languages and adapted for use in multiple other settings, including the ICU (CAM-ICU), nursing homes (NH-CAM), and Emergency department (B-CAM).[1][3][7] The CAM has also been used in research settings. It has been found to predict poor outcomes in patients.[1]

Elements of Score

The CAM consists of two parts. The first tests for overall cognitive impairment relating to 9 features of delirium based on the DSM: acute onset, disorganized thinking, inattention, altered level of consciousness, disorientation, memory impairment, perceptual disturbances, psychomotor agitation or retardation, and altered sleep-wake cycle. The second part is used for the diagnosis and is made up of the four features best able to identify delirium.[1][8]

Confusion Assessment Method Diagnostic Algorithm
Positive Result Criteria Assessment
Both A and B A. Acute onset and fluctuating course Typically requires information from a family member or nurse. Shown by a yes to one of the following questions:
  • "Is there evidence of an acute change in mental status from the patient's baseline?
  • "Did the abnormal behavior come and go or change in severity during the day?"
B. Inattention Shown by a yes to the following question:
  • "Did the patient have difficulty focusing attention, for example, being easily distractible or having difficulty keeping track of what was being said?"
Plus either C or D C. Disorganized thinking Shown by a yes to the following question:
  • "Was the patient's thinking disorganized or incoherent, such as rambling or irrelevant conversation, unclear or illogical flow of ideas, or unpredictable switching from subject to subject?"
D. Altered level of consciousness Shown by any answer other than "alert" to the following:
  • "Overall, how would you rate this patient's level of consciousness?"
    • Alert (normal)
    • Vigilant (hyperalert)
    • Lethargic (drowsy, easily aroused)
    • Stupor (difficult to arouse)
    • Coma (unarousable)

Interpretation

A positive CAM was reported in the original validation study to have a sensitivity and specificity of 94–100% and 90–95% respectively for the presence of delirium.[6] Some studies have reported lower sensitivities for the test in clinical use and when used by nurses.[9][10][11][12][13][14] It is recommended that clinician judgement be applied as well when using the CAM to screen for delirium.[1][5] While it may be used to assess for the presence of delirium, it is not useful to determine the severity of delirium or to monitor for clinical improvement or worsening.[3]

Adaptations

CAM-ICU

Because of the high rates of delirium among patients in the ICU, a version of the CAM has been developed to allow assessment of critically ill patients. It maintains the same criteria, but removes the need for verbal responses to questions to allow assessment of patients on ventilators. It includes the Richmond Agitation-Sedation Scale to determine if a patient is too sedated to be assessed and to fulfill the criteria for altered level of consciousness.[15] The score has a sensitivity of 95–100% and specificity of 89–93%. However, it is not as sensitive compared with the CAM in patients who can talk.[1]

Other

The Brief CAM (B-CAM) is used to detect delirium in Emergency department patients and can be done in under 2 minutes. The Delirium Index (DI) and the CAM-S can measure the severity of delirium. The Preschool CAM-ICU and Pediatric CAM-ICU utilize picture cards, age-appropriate questions, and observation of a child's behavior to allow the detection of delirium in younger patients. The One Day Fluctuation Scale is used for detecting changes in the status of patients with Lewy Body Dementia.[1][15] The 3D-CAM is a method to assess for delirium in under 3 minutes.[7]

References
  1. Wei, Leslie A.; Fearing, Michael A.; Sternberg, Eliezer J.; Inouye, Sharon K. (May 2008). "The Confusion Assessment Method: A Systematic Review of Current Usage: CAM: A SYSTEMATIC REVIEW OF CURRENT USAGE". Journal of the American Geriatrics Society. 56 (5): 823–830. doi:10.1111/j.1532-5415.2008.01674.x. PMC 2585541. PMID 18384586.
  2. Inouye, Sharon K. (1990-12-15). "Clarifying Confusion: The Confusion Assessment Method". Annals of Internal Medicine. 113 (12): 941–8. doi:10.7326/0003-4819-113-12-941. ISSN 0003-4819. PMID 2240918.
  3. Grover, Sandeep (2012). "Assessment scales for delirium: A review". World Journal of Psychiatry. 2 (4): 58–70. doi:10.5498/wjp.v2.i4.58. ISSN 2220-3206. PMC 3782167. PMID 24175169.
  4. Inouye, S. K.; van Dyck, C. H.; Alessi, C. A.; Balkin, S.; Siegal, A. P.; Horwitz, R. I. (1990-12-15). "Clarifying confusion: the confusion assessment method. A new method for detection of delirium". Annals of Internal Medicine. 113 (12): 941–948. doi:10.7326/0003-4819-113-12-941. ISSN 0003-4819. PMID 2240918.
  5. Shi, Qiyun; Warren, Laura; Saposnik, Gustavo; MacDermid, Joy C. (2013-09-19). "Confusion assessment method: a systematic review and meta-analysis of diagnostic accuracy". Neuropsychiatric Disease and Treatment. 9: 1359–70. doi:10.2147/ndt.s49520. PMC 3788697. PMID 24092976. Retrieved 2020-11-03.
  6. "UpToDate". www.uptodate.com. Retrieved 2020-11-03.
  7. "Screening for delirium with the Confusion Assessment Method (CAM) – NIDUS". Retrieved 2020-11-03.
  8. "Confusion Assessment Method (CAM)". Medscape. Retrieved 2020-11-05.
  9. Rohatgi, Nidhi; Weng, Yingjie; Bentley, Jason; Lansberg, Maarten G.; Shepard, John; Mazur, Diana; Ahuja, Neera; Hopkins, Joseph (December 2019). "Initiative for Prevention and Early Identification of Delirium in Medical-Surgical Units: Lessons Learned in the Past Five Years". The American Journal of Medicine. 132 (12): 1421–1430.e8. doi:10.1016/j.amjmed.2019.05.035. ISSN 1555-7162. PMID 31228413.
  10. Heinrich, Thomas W.; Kato, Hirotaka; Emanuel, Christopher; Denson, Steven (March 2019). "Improving the Validity of Nurse-Based Delirium Screening: A Head-to-Head Comparison of Nursing Delirium-Screening Scale and Short Confusion Assessment Method". Psychosomatics. 60 (2): 172–178. doi:10.1016/j.psym.2018.09.002. ISSN 1545-7206. PMID 31416628.
  11. Reynish, Emma L.; Hapca, Simona M.; De Souza, Nicosha; Cvoro, Vera; Donnan, Peter T.; Guthrie, Bruce (27 July 2017). "Epidemiology and outcomes of people with dementia, delirium, and unspecified cognitive impairment in the general hospital: prospective cohort study of 10,014 admissions". BMC Medicine. 15 (1): 140. doi:10.1186/s12916-017-0899-0. ISSN 1741-7015. PMC 5530485. PMID 28747225.
  12. Inouye, S. K.; Foreman, M. D.; Mion, L. C.; Katz, K. H.; Cooney, L. M. (2001-11-12). "Nurses' recognition of delirium and its symptoms: comparison of nurse and researcher ratings". Archives of Internal Medicine. 161 (20): 2467–2473. doi:10.1001/archinte.161.20.2467. ISSN 0003-9926. PMID 11700159.
  13. Rolfson, D. B.; McElhaney, J. E.; Jhangri, G. S.; Rockwood, K. (December 1999). "Validity of the confusion assessment method in detecting postoperative delirium in the elderly". International Psychogeriatrics. 11 (4): 431–438. doi:10.1017/s1041610299006043. ISSN 1041-6102. PMID 10631588.
  14. Shenkin, Susan D.; Fox, Christopher; Godfrey, Mary; Siddiqi, Najma; Goodacre, Steve; Young, John; Anand, Atul; Gray, Alasdair; Hanley, Janet; MacRaild, Allan; Steven, Jill (24 July 2019). "Delirium detection in older acute medical inpatients: a multicentre prospective comparative diagnostic test accuracy study of the 4AT and the confusion assessment method". BMC Medicine. 17 (1): 138. doi:10.1186/s12916-019-1367-9. ISSN 1741-7015. PMC 6651960. PMID 31337404.
  15. "Monitoring Delirium in the ICU". www.icudelirium.org. Retrieved 2020-11-06.
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