Integrating frailty and acute illness severity scoring for risk stratification in acute geriatric care: Review and practical guide

Table 1 Comparison of acute illness severity scores and frailty assessments: Characteristics, limitations, and complementary roles in geriatric care

Comparative domain	Acute illness severity scores	Frailty assessments
Core concept	Measures the physiological “load” (the acute insult)	Measures the biological “chassis” (the baseline reserve)
Primary clinical variables	SOFA: Organ dysfunction labs, hemodynamics, and GCS[43]. qSOFA: Rapid bedside clinical signs[45]. NEWS2: Routine bedside vital signs[52]. APACHE: Worst physiological values during the first 24 hours of ICU admission[60,61]	CFS: Clinical judgment and collateral history of the patient’s baseline function[72]. FI/eFI: Mathematical accumulation of health deficits extracted via medical records or EHR[70,79]
Temporal focus	Current physiological state (real-time or 24-hour window)	Pre-existing baseline state (e.g., functional status 2 weeks prior for CFS, or accumulated lifetime deficits for FI)
Key strengths	Highly standardized; universal language for triage; excellent for detecting rapid physiological deterioration	Captures biological age rather than chronological age; predicts capacity for functional recovery and long-term trajectory
Limitations in the geriatric population	SOFA: Pre-existing chronic organ dysfunction masks the true acute insult. qSOFA: Fixed SBP thresholds miss relative hypotension; GCS confounded by dementia/delirium. NEWS2: Chronic vital derangements cause alarm fatigue; blunted physiological responses lead to false negatives. APACHE: Linear age-weighting ignores biological reserve; lab-heavy scoring misses severe illness when systemic responses are blunted	CFS: Relies heavily on the availability and accuracy of collateral history. FI/eFI: Manual calculation is impractical during emergencies without automated EHR integration
Complementary role in integration	Identifies the immediate, life-threatening physiological derangement requiring urgent resuscitation	Determines the underlying biological reserve to withstand the acute insult, predicting functional recovery and guiding goals of care

APACHE: Acute Physiology and Chronic Health Evaluation; CFS: Clinical Frailty Scale; EHR: Electronic health records; FI: Frailty index; eFI: Electronic frailty index; GCS: Glasgow Coma Scale; ICU: Intensive care unit; NEWS2: National Early Warning Score 2; qSOFA: Quick Sequential Organ Failure Assessment; SBP: Systolic blood pressure; SOFA: Sequential Organ Failure Assessment.