FIDDI — Family ICU Delirium Detection Instrument

What this tool is and how to interpret its evidence

The Family ICU Delirium Detection Instrument, or FIDDI, is a five-item questionnaire designed for relatives who know the patient and may notice changes not apparent during a short professional encounter. It can be completed in under five minutes and was adapted from informant-focused delirium work for the adult intensive-care setting. Its intended role is to add family observation to routine clinical assessment, particularly when symptoms fluctuate.

The initial study involved 51 family members and examined usability, internal consistency and relationships with other measures. It did not test FIDDI against a blinded expert delirium diagnosis and therefore did not establish diagnostic sensitivity, specificity or a safe stand-alone threshold. Although the publication title uses the word validation, the evidence is best classified as instrument development with preliminary construct validation. The authors themselves called for clinical evaluation against an appropriate reference standard.

FIDDI merits an emerging-tool page because it is a named, purpose-built ICU instrument and family input is clinically valuable. The page must nevertheless state that it is a candidate adjunct, not a validated replacement for CAM-ICU, ICDSC or expert assessment. Five items, family completion and approximate timing can be described without reproducing the questions. No accuracy percentage should be inferred from internal consistency. Future independent studies should address feasibility across languages, family availability, pre-existing cognitive impairment and performance against contemporaneous specialist diagnosis.