How this calculator works
The deficit-accumulation approach codes each assessed health deficit from 0 to 1 and divides their sum by the number assessed. Partial deficits such as 0.5 are allowed when defined by the chosen protocol. Following Searle and colleagues, this tool requires at least 30 deficits, excludes missing items from both numerator and denominator, and does not invent a questionnaire or diagnostic cut-off. Deficit selection and coding must come from a validated protocol. The result is an estimate for information only and is not medical advice.
Formula
FI = sum of observed deficit ratings / number of observed deficits. Each rating must lie between 0 and 1.
Worked example
Eight full deficits among 40 assessed give FI 0.20. A coded sum of 7.5 among 30 gives 0.25.
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Frequently asked questions
Can I make my own symptom list?
A clinically meaningful index needs a suitable set of age-associated deficits spanning multiple systems and a consistent coding protocol.
What happens to missing items?
Leave them out of both the coded sum and the number assessed. Do not count missing as healthy.
Is FI the Clinical Frailty Scale?
No. The Clinical Frailty Scale is a different judgement-based instrument; its scores are not interchangeable with this ratio.