Developing and Validating the Health Literacy Scale for Migrant Workers: Instrument Development and Validation Study

Background: Research concerning health literacy among migrant workers in South Korea has been limited, especially given the lack of validated instruments and the lack of focus on the cultural diversity of migrant workers.

Objective: This study aimed to develop and validate a health literacy scale for unskilled migrant workers (HLS-MW) in South Korea.

Methods: We first generated a pool of potential items based on a literature review and in-depth interviews with 23 migrant workers. Subsequently, we reviewed empirical referents from the first step to select relevant medical terminologies and passages, ultimately choosing 709 words. The study team initially generated 35 items with 709 health-related terms through empirical referent reviews. After content validity testing by an expert panel, 28 items comprising 89 terms on the 2 subscales of prose and documents were selected for psychometric testing. Overall, 402 unskilled migrant workers in South Korea completed a web-based survey between August and September 2021, with 334 responses included in the final analysis. We used multiple analytic approaches, including exploratory factor analysis, Rasch analysis (item response theory), and descriptive analysis, to examine the new scale's validity and reliability.

Results: The final sample primarily included young male workers from South Asian countries. The HLS-MW yielded 2 factors: prose and documents. The item difficulty scores ranged from -1.36 to 2.56. The scale was reduced to 13 items (10 prose and 3 document items), with the final version exhibiting good internal reliability (Kuder-Richardson index=0.88; intraclass correlation coefficient=0.94, 95% CI 0.93-0.95) and test-retest reliability (r=0.74, 95% CI 0.57-0.92). HLS-MW scores differed significantly by Korean language proficiency (F2,331=3.54, P=.004).

Conclusions: The HLS-MW is a reliable and valid measure to assess health literacy among migrant workers in South Korea. Further studies are needed to test the psychometric properties of the HLS-MW in diverse migrant groups in South Korea while also establishing cutoffs to help identify those in need of health literacy support.