[ARTICLE] The Relationship of the FOUR Score to Patient Outcome: A Systematic Review -Full Text

Abstract

The Full Outline of UnResponsiveness (FOUR) score assessment of consciousness replaces the Glasgow Coma Scale (GCS) verbal component with assessment of brainstem reflexes. A comprehensive overview studying the relationship between a patient’s FOUR score and outcome is lacking. We aim to systematically review published literature reporting the relationship of FOUR score to outcome in adult patients with impaired consciousness. We systematically searched for records of relevant studies: CENTRAL, MEDLINE, EMBASE, Scopus, Web of Science, ClinicalTrials.gov, and OpenGrey. Prospective, observational studies of patients with impaired consciousness were included where consciousness was assessed using FOUR score, and where the outcome in mortality or validated functional outcome scores was reported. Consensus-based screening and quality appraisal were performed. Outcome prognostication was synthesized narratively. Forty records (37 studies) were identified, with overall low (n = 2), moderate (n = 25), or high (n = 13) risk of bias. There was significant heterogeneity in patient characteristics. FOUR score showed good to excellent prognostication of in-hospital mortality in most studies (area under curve [AUC], >0.80). It was good at predicting poor functional outcome (AUC, 0.80–0.90). There was some evidence that motor and eye components (also GCS components) had better prognostic ability than brainstem components. Overall, FOUR score relates closely to in-hospital mortality and poor functional outcome. More studies with standardized design are needed to better characterize it in different patient groups, confirm the differences between its four components, and compare it with the performance of GCS and its recently described derivative, the GCS-Pupils, which includes pupil response as a fourth component.

Introduction

Clinicians’ management decisions about acute traumatic brain injury (TBI) patients are guided by assessments of the person’s current state and may also be influenced by their perceptions of its relation to the patient’s likely outcome.¹ Internationally, the Glasgow Coma Scale (GCS) is the most widely used tool for assessing and communicating about a patient’s responsiveness.² All the three components—eye, motor, and verbal responses—relate to outcome,³ as does the derived summation into the GCS score, albeit with some loss of information. Moreover, the GCS is combined with other features, such as pupil response, age, and injury characteristics, in numerous multi-variate prognostic models for predicting functional outcome and mortality.^4–6 The difficulty in assigning a verbal response in an intubated patient and the separation of assessment of brain stem features, such as pupil response, in multi-variate modeling stimulated specialists in neurological intensive care to propose an alternative approach.

The Full Outline of UnResponsiveness (FOUR) score was described by Wijdicks and colleagues. It is based on the eye and motor components of the Glasgow system, but the verbal component was removed and two new components added, namely brainstem reflexes and respiratory pattern. The FOUR score was developed for the assessment of level of consciousness in patients admitted to a neurointensive care unit.⁷ This was with the purpose of improving the standardized assessment of level of consciousness for patients who are intubated or have focal neurological deficits. Each component is a 5-point scale, ranging from 0 to 4, with combined FOUR score ranging from 0 to 16, with 16 indicating the highest level of consciousness. Unlike the GCS, the eyes must be able to track or blink to command in order to obtain the maximum score of 4 points for eye component in FOUR score. Table 1 shows the scoring criteria for all components of FOUR score and GCS. The FOUR score approach emphasizes description of a patient by the combined score and the validity of the latter as an index of acute severity through its relationship to outcome. In order to provide a comprehensive assessment of the latter, we have performed a systematic review of the reported evidence, with focus on prognostic performance in groups of patients particularly targeted by FOUR score, namely those with a neurological diagnosis, intubated patients, and those admitted to dedicated neuroscience centers.

Table 1. Components of the FOUR Score and Glasgow Coma Scale

Full Outline of UnResponsiveness Score	Glasgow Coma Scale
Eye response 4 = eyelids open or opened, tracking, or blinking to command 3 = eyelids open but not tracking 2 = eyelids closed, but open to loud voice 1 = eyelids closed, but open to pain 0 = eyelids remain closed with pain	Eye opening 4 = spontaneous 3 = to speech 2 = to pain 1 = none
Motor response 4 = thumbs-up, fist, or peace sign 3 = localizing to pain 2 = flexion response to pain 1 = extension response to pain 0 = no response to pain or generalized myoclonus status	Best motor response 6 = obeying commands 5 = localizing to pain 4 = withdrawal from pain 3 = abnormal flexion response to pain 2 = extension response to pain 1 = none
Brainstem reflexes 4 = pupil and corneal reflexes present 3 = one pupil wide and fixed 2 = pupil or corneal reflexes absent 1 = pupil and corneal reflexes absent 0 = absent pupil, corneal and cough reflex	Verbal response 5 = orientated 4 = confused 3 = inappropriate words 2 = incomprehensible sounds 1 = none
Respiration 4 = not intubated, regular breathing pattern 3 = not intubated, Cheyne-Stokes breathing pattern 2 = not intubated, irregular breathing 1 = breathes above ventilator rate 0 = breathes at ventilator rate or apnea

FOUR, Full Outline of UnResponsiveness. […]

 

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