Interview Administration of PROMIS Depression and Anxiety Short Forms

Health literacy reflects a person's reading and numeracy abilities applied to understanding health-related information. These skills may influence how patients report symptoms, leading to underestimates or overestimates of symptom severity. No prior studies have examined health literacy measurement bias.

The purpose of the current study was to determine whether PROMIS (Patient-Reported Outcomes Measurement Information System) anxiety and depression short forms, administered by interview, capture symptoms equally across health literacy groups. We examined the psychometric properties of PROMIS anxiety and depression short forms using differential item functioning (DIF) analysis by level of health literacy.

The sample analyzed included 888 adults, age 55 to 74 years, in Chicago, IL. Health literacy was measured using the Test of Functional Health Literacy in Adults. PROMIS short forms assessed anxiety and depression.

DIF was present in 3 of 8 depression items, and 3 of 7 anxiety items. All items flagged for DIF had lower item-slopes for people with limited health literacy.

Items with DIF were less strongly related to anxiety and depression, and thus less precise. Overall, impact of DIF on PROMIS scores was negligible, likely mitigated by interview administration. Although overall test impact of health literacy was minimal, DIF analyses flagged items that were potentially too complex for people with limited health literacy. Design and validation of patient-reported surveys should incorporate respondents with a range of health literacy and methods to identify and reduce measurement bias. [HLRP: Health Literacy Research and Practice. 2019;3(3):e196-e204.].

This study suggests that people with limited health literacy may respond differently to questions about depression and anxiety than people with adequate health literacy. Therefore, it is important to be aware of differences in literacy ability when creating and using questionnaires.