The Clinical Frailty Scale is a 9-point ordinal scale that grades frailty based on functional status 2 weeks before the current illness. It ranges from 1 (very fit) to 9 (terminally ill) and is widely used in acute care for prognostication, triage, and treatment escalation decisions.
inputs
✓ when to use
Use for all older adults (typically ≥65) presenting with acute illness, particularly in ED, acute medicine, ICU referral, and surgical pre-assessment. CFS should reflect BASELINE function (2 weeks pre-illness), not current acute presentation. Used to guide treatment escalation plans, critical care referral decisions, and shared decision-making about intervention intensity.
✗ when not to use
CFS assesses baseline functional status — do not score based on the patient's current acute illness state. Not validated in patients <65 or in specific conditions like stable disability from prior stroke (where CFS may overestimate frailty). CFS should not be used as a sole criterion for withdrawing or withholding treatment — it informs prognosis and supports shared decision-making, not binary clinical decisions.
clinical pearls
Always score CFS based on BASELINE function 2 weeks before acute illness — not the patient's current state. An active 75-year-old who arrives confused and immobile with pneumonia is still CFS 1–2 if that was their baseline.
CFS should be assessed by talking to the patient and/or their carers — it requires understanding of the patient's usual daily activities, not just a snapshot observation.
CFS is a prognostic tool, not a rationing tool. It provides important information for shared decision-making about treatment intensity and goals of care, but should never be the sole basis for limiting treatment.
During COVID-19, CFS gained widespread attention but was sometimes misapplied as a binary triage criterion. The BGS and NICE emphasised that CFS is one factor in individualised clinical assessment, not a standalone gatekeeper.
CFS correlates with but is distinct from age. A fit 85-year-old (CFS 1–2) has a very different prognosis from a frail 70-year-old (CFS 6–7). CFS adds prognostic information beyond what age alone provides.