A systematic review of methodological approaches and measurement of adherence to micronutrient supplementation among women of reproductive age in low- and middle-income countries.

backgroundEnsuring adherence to recommended micronutrient supplementation regimens is essential for addressing malnutrition among women in low- and middle-income countries (LMICs). While efficacy trials often use biomarker changes as proxies for adherence, public health programs employ diverse methodologies to measure adherence. However, consolidated evidence on the methodological approaches used in these programs and the extent of their standardization remains scarce. This systematic review addresses this gap by exploring adherence measurement methodologies, including adherence thresholds, data collection methods, the number of methods utilized, and measurement frequencies.

methodsWe conducted a literature search on PubMed, Scopus, and Embase. Studies that measured adherence to WHO-recommended micronutrient supplements among women aged 15–49 in LMICs were included. Two reviewers screened titles/abstracts and full texts independently. Fifty-nine articles met the criteria. Data extraction involved four researchers. Article quality was assessed using Cochrane tools.

resultsWe categorized the included studies into behavioral vs. non-behavioral interventions to identify unique patterns between the two. Across non-behavioral studies, adherence was frequently defined with a threshold of 80%. These studies commonly used pill count to measure adherence and conducted frequent monitoring. Behavioral studies often adopted more diverse thresholds (e.g., 70%, 90 tablets), while 67% of them did not provide a clear threshold to define adherence. Self-report was the most commonly used measurement approach. The use of data triangulation and regular monitoring bolstered the validity of self-reports.

conclusionsMicronutrient supplementation programs would benefit from adopting evidence-based thresholds to define adherence levels, enhancing comparability across studies. Using a combination of methods and cross-checking data from multiple sources can improve the validity of adherence measurements. We recommend against treating adherence as a static, standalone construct; instead, reporting its trajectory throughout an intervention and its association with health outcomes can provide valuable insights for program planning. In terms of study characteristics, most studies have primarily focused on pregnant and lactating women, leaving adherence measurement approaches among nonpregnant women and adolescents largely understudied. We strongly encourage future research to investigate how methodological issues of adherence is uniquely experienced among this underserved population.