Development of an Instrument to Measure Dietary Supplement Health Literacy

Health literacy is one of the important social determinants of health.

The aim of this study was to develop an instrument to measure Dietary Supplement Health Literacy (DSHL) of Iranian women.

In this psychometrics study, an initial nine-factor instrument was developed. Face validity and content validity of the instrument were evaluated. The factor structure of the instrument was explored by the Exploratory Factor Analysis (EFA) among 400 women taking Dietary supplement. Confirmatory Factor Analysis (CFA) was done to determine the underlying factor structure of the instrument in this population. The internal and external reliability of the instrument was evaluated.

According to expert panel opinions, 16 items were deleted. The results of the EFA showed that the Kaiser-Meyer-Olkin and Bartlett's test of sphericity were significant. EFA showed that 30 items could be grouped into nine factors that accounted for 60.84% of the variance. Since two items in the ability to actively engage with health care providers factor were loaded in factor 1, this factor was labeled Engaging in receiving informational supports from health care providers. In addition, one item of the dimension was loaded in factor 3. Given that the one item of factor 5 and 1 item of factor 6 were loaded in a new factor 9, this factor was labeled Applying information to decision-making. The CFA indicated that the nine-factor structure of the DSHL instrument had a poor fit. To modify indices, factor 9 with 2 items and 1 item of factor 6 were deleted. The Cronbach's alpha and intraclass correlation coefficient of the instrument were acceptable. Finally, a 27-item instrument with 8 dimensions was confirmed.

The results of the study showed that the instrument developed was a valid tool for identifying the DSHL of Iranian women. [] Plain Language Summary: This study sought to develop and validate a multidimensional instrument to measure the health literacy of Iranian women about dietary supplements that was performed from July 2019 to May 2020 in Iran. Findings showed that the 30-item instrument developed in this study is a valid instrument to be used for identifying the health literacy of Iranian women about dietary supplements.