Replacing GCS With FOUR in ICU Severity Scores: Derivation and Validation of Modified APACHE, SAPS, MODS, LODS, and SOFA Models

Intensive care units (ICUs) are highly complex, resource and technology intensive settings. During the 1970s and 1980s, increasing intensive care costs and poor outcomes among patients with multiple organ failure created a need for tools to measure illness severity and patient outcomes. Intensive care unit mortality varies considerably worldwide, with rates of 16.2% in large international study and 19.1% in a European cohort study, while higher mortality was reported in developing countries, Ethiopia (39.06%) and Iraq (29.8%).

The Glasgow Coma Scale (GCS) assesses impaired consciousness using eye opening, verbal, and motor responses and is widely used for assessment, triage, monitoring, and communication among healthcare professionals. It has several limitations, verbal component cannot be assessed reliably in patients who are intubated, pharmacologically sedated, or unable to speak, limiting the use of the total score for prognosis. Also has limitation in evaluation patients with concomitant head and spinal cord injury. Drug and alcohol intoxication can also affect GCS assessment and should be considered when interpreting scores. In addition, Aphasia, paralysis, neuromuscular weakness, and spinal injuries may impair verbal or motor responses independently of consciousness, while painful stimuli can complicate scoring in polytrauma patients. Its reliability depends on assessor training, the patient's consciousness level, and the type of stimulus used.

The Full Outline of UnResponsiveness (FOUR) score consisting of four components: eye response, motor response, brainstem reflexes, and respiration, with each component assigned a maximum score of 4. It showed excellent interrater reliability (weighted kappa = 0.82), and provide greater neurological detail and identification of severe impairment than GCS. In non-traumatic patients, FOUR score showed better mortality discrimination than GCS (AUROC 0.799 vs. 0.731), and offers advantages in intubated patients because it evaluates brainstem reflexes and respiratory patterns. FOUR also showed better mortality prediction than GCS in traumatic brain injury, neurosurgical, and acute brain-injury patients, with AUROC values of 0.93 vs. 0.89, 0.768 vs. 0.699, and 0.835 vs. 0.772, respectively.

The Acute Physiology and Chronic Health Evaluation (APACHE) assess risk of in-hospital by using pre-admission health status and 34 physiological variables collected during the first 24 hours of ICU admission. The Acute Physiology and Chronic Health Evaluation II (APACHE II) uses 12 physiological variables, along with age and previous health status, to calculate a score from 0-71, with higher scores indicating greater illness severity and mortality risk. APACHE III incorporated over 100 variables, while APACHE IV added further clinical factors and enabled prediction of hospital mortality and ICU length of stay.

The Simplified Acute Physiology Score (SAPS) includes14 physiological variables collected during the first 24 hours of ICU admission to provides a simple measure of the risk of death among critically ill patients. The Simplified Acute Physiology Score II (SAPS II) provide an objective assessment of illness severity and an estimate of hospital mortality among critically ill patients. SAPS II involve 17 variables, including 12 physiological measurements, age, type of ICU admission, and three underlying disease conditions: acquired immunodeficiency syndrome, metastatic cancer, and hematologic malignancy. SAPS 3, incorporated 20 variables and provided region-specific mortality prediction for international use.