The 2014 updated version of the Confusion Assessment Method for the Intensive Care Unit compared to the 5th version of the Diagnostic and Statistical Manual of Mental Disorders and other current methods used by intensivists

Abstract

Background: One third of patients admitted to an intensive care unit (ICU) will develop delirium. However, delirium is under-recognized by bedside clinicians without the use of delirium screening tools, such as the Intensive Care Delirium Screening Checklist (ICDSC) or the Confusion Assessment Method for the ICU (CAM-ICU). The CAM-ICU was updated in 2014 to improve its use by clinicians throughout the world. It has never been validated compared to the new reference standard, the Diagnostic and Statistical Manual of Mental Disorders 5th version (DSM-5).

Methods: We made a prospective psychometric study in a 16-bed medical-surgical ICU of a French academic hospital, to measure the diagnostic performance of the 2014 updated CAM-ICU compared to the DSM-5 as the reference standard. We included consecutive adult patients with a Richmond Agitation Sedation Scale (RASS) ≥ -3, without preexisting cognitive disorders, psychosis or cerebral injury. Delirium was independently assessed by neuropsychological experts using an operationalized approach to DSM-5, by investigators using the CAM-ICU and the ICDSC, by bedside clinicians and by ICU patients. The sensitivity, specificity, positive and negative predictive values were calculated considering neuropsychologist DSM-5 assessments as the reference standard (primary endpoint). CAM-ICU inter-observer agreement, as well as that between delirium diagnosis methods and the reference standard, was summarized using κ coefficients, which were subsequently compared using the Z-test.

Results: Delirium was diagnosed by experts in 38% of the 108 patients included for analysis. The CAM-ICU had a sensitivity of 83%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 91%. Compared to the reference standard, the CAM-ICU had a significantly (p < 0.05) higher agreement (κ = 0.86 ± 0.05) than the physicians,' residents' and nurses' diagnoses (κ = 0.65 ± 0.09; 0.63 ± 0.09; 0.61 ± 0.09, respectively), as well as the patient's own impression of feeling delirious (κ = 0.02 ± 0.11). Differences between the ICDSC (κ = 0.69 ± 0.07) and CAM-ICU were not significant (p = 0.054). The CAM-ICU demonstrated a high reliability for inter-observer agreement (κ = 0.87 ± 0.06).

Conclusions: The 2014 updated version of the CAM-ICU is valid according to DSM-5 criteria and reliable regarding inter-observer agreement in a research setting. Delirium remains under-recognized by bedside clinicians.

Keywords: Critical care; Delirium; Intensive care unit.

Fig. 1

Study design. The order of assessments by the research team was determined to check both the patient’s eligibility and the presence of some CAM-ICU and ICDSC features (i.e., fluctuating course of mental status assessed by RASS ratings). ICDSC was assessed after CAM-ICU because ICDSC included some CAM-ICU features (i.e., inattention). RASS Richmond Agitation Sedation Scale, CAM-ICU Confusion Assessment Method for the Intensive Care Unit, ICDSC Intensive Care Delirium Screening Checklist, DSM-5 5th version of the Diagnostic and Statistical Manual of Mental Disorders

Fig. 2

Agreement between different delirium assessment methods and the neurological experts’ reference rating using the DSM-5 criteria. This figure shows the graphic representation of kappa coefficients and their standard deviations for each of the methods used to assess delirium. The kappa coefficient measured the agreement between each of the methods and the assessment by the neuropsychologist experts using DSM-5 criteria (reference standard). For simple questions, we did not decide a priori how to analyze the answers. Because some patients answered some questions but did not answer other ones, we decided a posteriori to analyze these data following two approaches: including all patients and including only the patients able to answer all the questions. Several thresholds were tested, i.e., delirium was defined in all patients if they gave at least 1 or 2 false or no response(s), or, among the patients who were able to answer all simple questions, if the patients gave at least 1 or 2 false response(s). There was a significant difference (p < 0.047) between the CAM-ICU and each of the other methods, except the ICDSC (p = 0.054). There were significant differences between “all methods from CAM-ICU to ≥ 1 false response to simple questions” and “patient’s own impression of feeling delirious,” as well as between “all methods from CAM-ICU to nurse diagnosis” and “≥ 2 false responses to simple questions” or “patient’s own impression of feeling delirious.” *: Significant difference (p < 0.05); CAM-ICU Confusion Assessment Method for the Intensive Care Unit, ICDSC Intensive Care Delirium Screening Checklist