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.

Table 2 Key primary studies evaluating the dual-axis assessment and prognostic integration of baseline frailty and acute illness severity scores

Ref.	Study design (n)	Scoring systems	Key findings
Emergency department
Chung et al[82], 2025	Retrospective multi-center (n = 932)	CFS and (NEWS2, qSOFA, REMS)	Combined assessment significantly improved AUROC for predicting hospital admission, ICU admission, and in-hospital mortality (mortality AUROCs 0.77-0.82) compared to isolated scores
Wretborn et al[83], 2024	Prospective multi-center (n = 1832)	CFS and (NEWS, TEWS, RETTS)	Combined assessment significantly improved the AUROC for short-term mortality prognostication (0.53 to 0.82) compared to isolated early warning and triage tools (e.g., NEWS)
Engvig et al[87], 2022	Prospective single-center (n = 195)	CFS and NEWS2	Combined assessment revealed a significant interaction effect (P = 0.003), demonstrating that the prognostic impact of frailty is greater at higher levels of acute illness severity compared to isolated scores
Biuzzi et al[88], 2026	Retrospective single-center (n = 70)	CFS and NEWS2	Combined assessment successfully identified highly frail patients at risk for in-hospital cardiac arrest who presented with deceptively low acute physiological scores
Intensive care unit
Le Maguet et al[2], 2014	Prospective multi-center (n = 196)	FP and SAPS II, CFS and SOFA	Multivariate analysis demonstrated that FP and SAPS II independently predict short-term mortality, while CFS and SOFA concurrently predict long-term mortality
Bagshaw et al[91], 2014	Prospective multi-center (n = 421)	CFS and (SOFA, APACHE II)	Multivariable analysis confirmed that frailty is independently associated with higher in-hospital and long-term mortality after adjusting for SOFA and APACHE II scores. Highlighted mortality increased in a dose-dependent manner with each incremental increase in the frailty score
Guidet et al[92], 2020	Prospective multinational (n = 3920)	CFS and SOFA	Both scores act as powerful, independent predictors of short-term mortality, reinforcing the necessity of dual-axis risk stratification
Haas et al[93], 2021	Prospective multinational (n = 532; sepsis subset of VIP2)	CFS and SOFA	Within the septic sub-cohort, SOFA and CFS scores act as robust, independent predictors of long-term mortality
Bruno et al[94], 2023	IPD meta-analysis (n = 23989)	CFS and SOFA	In geriatric cohort (≥ 65 years), frailty remains a robust, independent predictor of ICU mortality alongside the SOFA score. Highlighted a “frailty continuum” where risk increases progressively across CFS categories
Zeng et al[95], 2015	Prospective single-center (n = 155)	FI and (APACHE II, APACHE IV)	FI captures essential premorbid functional data, increasing the AUROC for mortality from 0.86 to 0.92 (APACHE II) and 0.88 to 0.93 (APACHE IV)
Szűcs et al[84], 2025	Prospective single-center (n = 212)	CFS and (APACHE II, SAPS II)	Integrating the CFS significantly increased the AUROC for mortality from 0.72 to 0.80 (APACHE II) and from 0.79 to 0.84 (SAPS II)
Suh et al[96], 2025	Retrospective multi-center (n = 8220)	CFS and APACHE III-J	Both tools remained strong independent predictors of mortality and prolonged hospitalization in critically ill nonagenarians
Langlais et al[97], 2018	Prospective single-center (n = 189)	CFS and SOFA	Integration of CFS and SOFA yielded a non-significant AUROC improvement for mortality (0.63 to 0.66, P = 0.082)

APACHE: Acute Physiology and Chronic Health Evaluation; AUROC: Area under the receiver operating characteristic curve; CFS: Clinical Frailty Scale; ED: Emergency department; FI: Frailty Index; FP: Frailty phenotype; ICU: Intensive care unit; IPD: Individual patient data; NEWS: National Early Warning Score; NEWS2: National Early Warning Score 2; qSOFA: Quick Sequential Organ Failure Assessment; REMS: Rapid Emergency Medicine Score; RETTS: Rapid emergency triage and treatment system; SAPS II: Simplified Acute Physiology Score II; SOFA: Sequential Organ Failure Assessment; TEWS: Triage Early Warning Score.

Table 3 Phenotype-specific clinical implications: Triage, treatment intensity, and goals of care

Clinical phenotype	Triage and disposition	Treatment intensity	GOC strategy
Low risk	Standard ward	Routine monitoring: Focus on preventing functional decline	Goal alignment: Align treatment with baseline patient goals and functional priorities
Masked resilience	ICU/HDU	Full escalation: Aim for return to robust baseline	Justification: Explain how robust reserve justifies intensive care
Masked risk	AGU	High vigilance: Preserve function; prevent delirium	Proactive warning: Highlight “silent severity” and the high risk of rapid functional decline
High risk	ICU/HDU or AGU	Proportionality: TLT of intensive care	Thresholds: Shift focus to dignity if biological limits are met

GOC: Goals of care; HDU: High dependency unit; AGU: Acute geriatric unit; ICU: Intensive care unit; TLT: Time-limited trial.