Frontotemporal Dementia Rating Scale
Thirty informant-rated items covering behaviour and everyday function. Each is marked A (all the time), B (sometimes) or C (never), with NA where the activity did not apply before illness. The tool computes the preserved-function percentage and severity category live, and shows which functional areas are carrying the loss.
Rate every item to produce a score. A and B both score 0; only C — never — scores 1.
Band widths are drawn to scale, so the compression at the preserved end is real: a single item flipping from C to B can move a mildly affected person a whole category.
Percentage of applicable items in each area still rated “never”. Areas with every item marked NA are shown as not applicable.
Scoring collapses A and B to zero, so the split between them does not affect the total — but it is kept here because a profile weighted to A rather than B describes a different clinical picture at the same score.
Scoring. A and B both score 0; C scores 1. Items marked NA are removed from the denominator, so the maximum equals the number of applicable items answered. Score = total ÷ maximum × 100, rounded to the nearest whole number for band assignment.
Percentage and logit. Both are deterministic functions of the same raw total, so the logit adds nothing to a single rating — the reason to show it is that it is interval-scaled and the percentage is not. Equal percentage steps are not equal amounts of change: 90% to 95% spans 0.49 logits, 45% to 50% spans 0.36. Longitudinal change, annualised decline and group comparisons should be computed on the logit; the percentage is fine for reporting a single assessment. Logit values are taken from the FRS conversion table (Mioshi et al., 2010).
Two boundary quirks. 40% and 41% both convert to −0.40 logits but fall either side of the severe/moderate cut, so a category change across that point reflects no change in the underlying metric. Separately, the very mild band (97–99%) is unreachable when fewer than 30 items are applicable: with 28 items, one item moving off “never” takes the score straight from 100% to 96%. Neither is a fault in the tool — both are properties of mapping a small integer count onto a percentage scale.
Categories. Bands follow the conversion table, with 100% labelled asymptomatic rather than very mild, following GENFI practice.
Scoring aid only. It does not constitute a diagnosis or a staging determination, and it should not be used in place of clinical assessment.