Faces Scales for Anxiety and Anger: A National Study of Measurement Properties

Importance: Faces scales are used worldwide to assess pain, but robust faces scales for anxiety and anger do not exist. These scales are urgently needed, because an estimated two-thirds of patients have difficulty reading written questionnaires.

Objective: To develop and evaluate measurement properties of faces scales to monitor two mental health symptoms in US adults (anxiety and anger) in accordance with the COnsensus-based Standards for health Measurement INstruments (COSMIN).

Methods: The development process included population identification, scale generation, and pretesting. The evaluation process included assessment of content validity, construct validity, criterion validity, test-retest reliability, and measurement error using 5 order-randomized, positively controlled online survey studies conducted between April and June 2020. We recruited national purposive samples of US adults representative on age, gender, and race. For each faces scale, participants assessed relevance, comprehensibility, and comprehensiveness (study 1, n = 300), strength-of-association (study 2, n = 300), convergent validity against the visual analog scale (VAS; study 3, n = 305), convergent validity against the Patient-Reported Outcomes Measurement Information System (PROMIS) questionnaires (study 4, n = 1,000), and test-retest reliability and measurement error (study 5, n = 853).

Results: The anxiety and anger faces scales showed high relevance (95%-96%), comprehensibility (93%-97%), comprehensiveness (94%-97%), and strength-of-association (74%-96%). We found very high agreement with the VAS (ρ = 0.94-0.95) and high agreement with PROMIS questionnaires (ρ = 0.74-0.79). Scales showed adequate test-retest reliability (intraclass correlation = 0.70-0.78) and measurement error (standard error of measurement = 1.14-1.22).

Conclusions: Faces scales to monitor anxiety and anger show adequate measurement properties, including content validity, construct validity, criterion validity, test-retest reliability, and measurement error. The recommended use is non-diagnostic monitoring of anxiety and anger, particularly when mental health is an ancillary but important outcome of treatment.