Confusion Assessment Method for the Intensive Care Unit for Diagnosing Delirium in Adults in Critical Care Settings

How accurate is the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) for diagnosing delirium in adult patients in critical care units?Delirium is a behavioral manifestation of acute brain dysfunction that is common in ICUs, affecting from 31% to 80% of critically ill patients.1,2 Characterized by inattention, altered consciousness, and disorganized thinking, delirium is associated with several serious adverse outcomes including longer duration of mechanical ventilation, increased ICU and hospital length of stay, long-term cognitive impairment, and higher risk of death.3 Thus, a validated, effective, and user-friendly tool is needed to help assess delirium so that clinical teams can provide timely and adequate treatment. One such tool, recommended by the Society of Critical Care Medicine, is the CAM-ICU.4The CAM-ICU has its origins in the Confusion Assessment Method (CAM), which was developed in 1990 to assist nonpsychiatrists in performing bedside delirium assessments. In 2001, the CAM-ICU was derived from the CAM to help screen for delirium in ICU patients both receiving and not receiving mechanical ventilation.5 As with the CAM, the CAM-ICU was designed to be completed by bedside clinical teams (eg, nurses and physicians) in 1 to 3 minutes.6 The screening process includes a series of questions and commands to assess for various elements of delirium and can be performed even if the patient cannot speak. The approach used in the ICU setting consists of 2 stages. In the first stage, the clinician measures the patient’s level of consciousness with a validated tool such as the Richmond Agitation-Sedation Scale and decides whether the patient can continue to the CAM-ICU screening or is too sedated for further assessment, in which case plans are made to reassess at a later time. In the second stage, the clinician uses the CAM-ICU to assess for acute changes in 4 areas of consciousness: mental status, attention, level of consciousness (using a sedation assessment tool), and thinking. The results guide the clinician to either a “positive” (delirium present) or a “negative” (delirium not present) determination.7Given the widespread use of the CAM-ICU, the purpose of the systematic review conducted by Miranda et al8 was to determine how accurately the tool could screen for delirium in adult patients in critical care units. In studies assessing the accuracy of diagnostic tests, both sensitivity and specificity are evaluated. Sensitivity refers to how well the test can determine that a case is positive (in this situation, the presence of delirium). When a test is highly sensitive, there are minimal false-negative results, meaning that fewer cases are missed. Specificity refers to how well the test can determine that the case is negative (in this situation, the absence of delirium). When a test is highly specific, there are minimal false-positive results. Both sensitivity and specificity are important factors in determining the risks and benefits of relying on test results. Both values are calculated as a percentage, with 100% being the maximum; the higher a test’s sensitivity and specificity, the more accurate it is in diagnosing the condition.9The systematic review conducted by Miranda et al8 included 25 studies investigating the diagnostic accuracy of the CAM-ICU. These studies involved a total of 2817 adult participants (aged ≥18 years). Miranda et al8 independently assessed the risk of bias for each study, including selection, performance, detection, attrition, reporting, and publication biases. Any disagreements were resolved by reviewing the data together and through discussion.The methodological quality of the studies was assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) tool, which is used to evaluate 4 domains: patient selection, index testing, reference standards, and patient involvement in the process. Most of the studies were assessed as having a low risk of bias in all 4 domains, with a few studies having either unclear or high risk in 1 domain. The authors calculated the overall median prevalence of delirium and the sensitivity and specificity of the CAM-ICU with 95% CIs.8Of the 2817 ICU patients included in the studies, 1022 were classified as having delirium. In the individual studies, the prevalence of delirium ranged from 12.5% to 83.9%, with a median prevalence of 40%.The pooled sensitivity was 0.78 (95% CI, 0.72-0.83). With a prevalence of 40%, 400 out of 1000 patients would be positive for delirium with use of the CAM-ICU, and 87 could be missed (false negatives).The pooled specificity was 0.95 (95% CI, 0.92-0.97). With a prevalence of 40%, 600 out of 1000 patients would not be positive for delirium with use of the CAM-ICU, and 30 could be incorrectly screened as positive (false positives).There continues to be a large number of adult ICU patients who experience delirium and, thus, a need for an evidence-based, valid screening tool. Many studies have supported the use of the CAM-ICU for screening for delirium in adult ICU patients, and the systematic review by Miranda et al8 investigated the diagnostic accuracy of the tool. Both the sensitivity and specificity were good, with specificity being higher at 95%. Although there is a risk of patients with delirium being missed (false negatives), this risk would likely be mitigated in clinical practice given that the CAM-ICU is completed at least daily. The results of the systematic review of Miranda et al8 aligned with those of previous studies on the CAM-ICU and showed that although the sensitivity and specificity of the tool are high, they are not 100%. This finding supports the need to use any diagnostic test in combination with other approaches.10 Given that the CAM-ICU is not 100% accurate, it is best used in combination with the clinical expertise of an interprofessional team to determine the best course of action for a particular patient.An important consideration is that the availability of an effective tool does not ensure that it is administered as intended. A 2021 study11 explored the accuracy of CAM-ICU documentation over a year, with more than 28 000 documentation opportunities. The results showed that documentation was completed in only 66% of cases and that the frequency of documentation as “unable to assess” was higher than anticipated. As with many assessments and screenings, one of the main challenges is allocating the necessary time to conduct and document the CAM-ICU appropriately.11 The systematic review by Miranda et al8 did not explore how clinical teams were trained or the best methods for sustaining the practice, which could be targets of future study.The evidence from this systematic review may affect the decisions of clinical care teams in creating treatment plans for patients at risk for delirium. As nurses caring for critically ill patients, we must regard advocating for the best evidence-based treatment as an important part of our role. We must always consider the best available evidence and understand the feasibility, appropriateness, meaningfulness, and effectiveness of any intervention to determine whether it is most appropriate to implement in our individual context.