Questionnaires in Drug Evaluation

Definition, scope & role in drug evaluation

• Definition — A questionnaire (more broadly a self-reported measure) is an instrument in which participants describe their own symptoms, functioning, behaviours, attitudes or quality of life — as distinct from data measured objectively by an observer, device or assay. In a drug trial the questionnaire is the measurement instrument for a subjective endpoint, so the validity of the efficacy/safety read-out depends on how well it is designed.
• Subjective outcomes it uniquely captures — Symptoms (frequency/severity/intensity) · health-related quality of life (HRQoL) and functioning · treatment satisfaction · medication adherence (self-recall of intake) · patient-reported tolerability / symptomatic ADRs (nausea, dizziness, sexual dysfunction) defined primarily by the patient's perception.
• Irreplaceable role — Some conditions and treatment effects are defined primarily by the patient's perception — generalized anxiety disorder, irritable bowel syndrome, insomnia (sleep quality, daytime sleepiness) — for which self-reported instruments are "the best, if not the only, measure"; physiologic surrogates (actigraphy, accelerometry) cannot replace them.
• Patient-reported outcome (PRO) — In the regulatory framing a PRO is any report of a patient's health-condition status that comes directly from the patient, without interpretation by a clinician or anyone else; the FDA reviews PRO instruments used to support claims in approved drug labeling. [FDA]
• Scope boundary — The focus is the measurement instrument — designing, selecting, administering and validating questionnaires that quantify subjective endpoints — not the overall study design (RCT/cohort) or objective endpoints (laboratory, imaging, hard clinical events), which are separate topics.