New Systematic Review of Instruments for Identification of Delirium

Contributed by Benjamin K. I. Helfand, MSc, MD/PhD (candidate), University of Massachusetts Medical School

Delirium affects approximately 3 million older Americans annually, accounting for over $164 billion in healthcare expenditures.1 Delirium disproportionately affects our older population (over age 65) with major public health implications. Development of delirium is associated with prolonged hospitalization, cognitive decline, and heightened risks for dementia and death.2,3 Due to difficulties in detection, delirium may go unrecognized, representing missed opportunities for its early detection and management.4,5 The challenges in recognizing delirium are in part due to the lack of a single accepted diagnostic approach.6 Fortunately, the medical community has brought an awareness to the seriousness of delirium. However, given the lack of biomarkers or laboratory confirmation, delirium remains a purely clinical diagnosis. This has led to the creation of many different instruments to aid in its detection. There are over 40 delirium-specific instruments used for different purposes (e.g., severity, diagnosis, and screening), targeting different clinical settings (e.g., medical and surgical wards, emergency department, intensive care unit (ICU)), and intended for different users (e.g., nurses, internists, geriatricians, psychiatrists). Each instrument describes varying signs and symptoms of delirium. The overwhelming number of instruments hinders interpretation and comparisons when different instruments are used, which has important clinical and research ramifications.

NIDUS is happy to highlight a new systematic review of delirium identification instruments recently published on November 2, 2020 in the Journal of the American Geriatrics Society, entitled “Detecting delirium: A systematic review of identification instruments for non-ICU settings.” This manuscript provides a comprehensive review of delirium identification instruments (defined as those used for screening or diagnosis). The overall goal of the study was to find all the instruments used for identification of delirium and evaluate the instruments according to their psychometric properties and frequency of citation in published research. Then, an expert panel recommended instruments based on citations, quality rating, and alignment with DSM criteria.

The systematic review was conducted in multiple steps. The first step involved searching CINAHL, Cochrane, EMBASE, PsycINFO, PubMed, and Web of Science from January 1, 1974-January 31, 2020, with the key words “delirium” and “instruments,” along with their known synonyms. Only review articles that described multiple delirium instruments were included. Two reviewers worked to extract data on all potential delirium identification instruments noted within these review articles. We also queried our expert panel and conducted hand searches of the included articles to find any other potential instruments. In the second step, each of the original publications of the instrument was found and its citation count was noted from Scopus. Each instrument had its psychometric properties extracted from the original publication using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) framework. The COSMIN score, rated from 0-6, assessed ratings of effect indicators, internal consistency, content validity, inter-rater reliability, construct/convergent validity, and criterion validity.

In the final step, an interdisciplinary expert panel was formed that included experts from geriatric medicine, geriatric psychiatry, cognitive neurology, gerontological nursing, and social work. The expert panel helped to determine the key domains (signs or symptoms) in identifying delirium used in each instrument. Then these domains were aligned with Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria. Additionally, the expert panel recommended excluding instruments designed specifically for use in the ICU, as these patients are often non-verbal and require a different set of assessment items. The expert panel chose citation count ≥200, COSMIN score >4, and meeting full DSM-5 criteria as the criteria for recommending an instrument. To be recommended, an instrument needed to meet at least 2 of these 3 criteria.

The systematic review yielded 2,542 articles, with 75 meeting eligibility criteria. After thorough review, 30 different delirium identification instruments were discovered in active use. After reviewing their citation count, undergoing COSMIN review, and alignment with DSM-5 criteria, the expert panel elected to recommend (alphabetically): Confusion Assessment Method (CAM), Delirium Observation Screening Scale (DOSS), Delirium Rating Scale-Revised-98 (DRS-R-98), and Memorial Delirium Assessment Scale (MDAS).

It is important to note that some newer instruments for delirium identification did not meet the expert panel criteria for inclusion (e.g., 3D-CAM and 4AT)—potentially because of their recent development. While the expert panel failed to recommend a single delirium identification instrument, they were able to recommend 4 instruments that can be broadly used by different users and for different clinical settings. The CAM can be used by trained lay interviewers as well as nurses or physicians. There are two versions that allow for either rapid or more in-depth assessment. CAM items can also be used to score severity. The DOSS provides a brief rating with minimal training designed for use in each shift by nurses. The MDAS and DRS-R-98 are both designed to be used by more trained professionals like psychiatrists, and allow for a more in-depth assessment, but require more time and resources. Additionally, they both can be used for either diagnostic or severity purposes.

An important area for future investigation, and one that is fortunately already underway, is to link the four selected instruments together using modern methods in psychometrics like item response theory. This will ultimately allow us to compare and combine multiple studies on delirium.


  1. Oh ES, Fong TG, Hshieh TT, Inouye SK. Delirium in older persons: Advances in diagnosis and treatment. JAMA. 2017;318(12):1161-1174.
  2. Breitbart W, Gibson C, Tremblay A. The delirium experience: delirium recall and delirium-related distress in hospitalized patients with cancer, their spouses/caregivers, and their nurses. Psychosomatics. 2002;43(3):183-194.
  3. MacLullich AM, Hall RJ. Who understands delirium? In: Oxford University Press; 2011:412-414.
  4. Inouye SK, Foreman MD, Mion LC, Katz KH, Cooney Jr LM. Nurses’ recognition of delirium and its symptoms: comparison of nurse and researcher ratings. Archives of internal medicine. 2001;161(20):2467-2473.
  5. Inouye SK, Bogardus Jr ST, Charpentier PA, et al. A multicomponent intervention to prevent delirium in hospitalized older patients. New England journal of medicine. 1999;340(9):669-676.
  6. Neufeld KJ, Nelliot A, Inouye SK, et al. Delirium diagnosis methodology used in research: A survey-based study. The American Journal of Geriatric Psychiatry. 2014;22(12):1513-1521.
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