Abstract
The Full Outline of UnResponsiveness (FOUR) score was developed to overcome the limitations of the Glasgow Coma Scale (GCS) when assessing individuals with impaired consciousness. We sought to review the evidence regarding the predictive validity of the GCS and FOUR score in intensive care unit (ICU) settings. This review was prospectively registered in PROSPERO (CRD42023420528). Systematic searches of CINAHL, MEDLINE, and Embase were undertaken. Prospective observational studies were included if both GCS and FOUR score were assessed in adults during ICU admission and if mortality and/or validated functional outcome measure scores were collected. Studies were excluded if they exclusively investigated patients with traumatic brain injury. Screening, data extraction, and quality assessment using the Quality in Prognosis Studies tool were conducted by two reviewers. Twenty studies of poor to moderate quality were included. Many studies only included patients with neurological illness and excluded sedated patients, despite high proportions of intubated patients. The FOUR score achieved higher area under the receiver operating characteristic curve values for mortality prediction compared with the GCS, and the FOUR score achieved significantly higher area under the receiver operating characteristic curve values for predictions of ICU mortality. Both coma scales showed similar accuracy in predicting “unfavorable” functional outcome. The FOUR score appeared to be more responsive than the GCS in the ICU, as most patients with a GCS score of 3 obtained FOUR scores between 1 and 8 due to preserved brainstem function. The FOUR score may be superior to the GCS for predicting mortality in ICU settings. Further adequately powered studies with clear, reliable methods for assessment of index and outcome scores are required to clarify the predictive performance of both coma scales in ICUs. Inclusion of sedated patients may improve generalizability of findings in general ICU populations.
Conclusions
The FOUR score may be superior to the GCS for prediction of ICU and hospital mortality for ICU patients with low levels of consciousness. The FOUR score offers additional advantages over the GCS when used in the ICU setting, including increased responsiveness, which may improve efficiency in identifying and responding to deterioration. Consideration should be given to the inclusion of the FOUR score in ICU mortality prediction models to improve calibration. The FOUR score presents a promising alternative to the GCS in the ICU setting; however, this review’s findings are limited by a lack of clinical diversity. Although many studies assessed only patients with neurological illnesses, this review did not include samples with large proportions of patients with TBI, and few studies included patients receiving sedation. Therefore, broader conclusions regarding the general applicability of the FOUR score for all ICU patients, including those with TBI and/or those receiving sedation, cannot be drawn from this review alone.
Further studies with robust methodologies are required to clarify the psychometric and predictive performance of the FOUR score and GCS in ICU settings. Future studies should include patients with nonneurological illness and those receiving sedation, alongside detailed reporting of patient characteristics (including disease severity and comorbidities). As more evidence emerges, meta-regression analyses may clarify the extent to which sedation influences the predictive abilities of the GCS and FOUR score in ICU settings and facilitate comparisons of their prognostic performance across various ICU subpopulations.
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