Study selection and data extraction
Two reviewers independently performed the selection of study, which was based on an initial screening of identified titles and abstracts and a second screening of full-text articles. Studies were considered eligible if they met the following criteria: (i) studies reporting anti-diabetic medication non-adherence or adherence and or factors associated with medication non-adherence; (ii) studies using observational study design (cross-sectional); (iii) studies conducted in LMICs as defined by the World Bank 9; (iv) studies written in English after year of 2000 and (v) published studies which were accessible with full text. We used the following exclusion criteria: studies conducted in high-income countries, studies with no information about adherence/non-adherence to anti-diabetic medications, studies assessing adherence to diet, studies with languages other than English, non-cross-sectional studies, and studies including other types of therapy than allopathic medicine to manage diabetes. Studies with incomplete information or no full text available were also excluded.
Two independent authors performed study screening and data extraction judiciously according to inclusion criteria. Any discrepancies were resolved through discussion of the third author until consent was achieved. A standard data extraction format was used to collect the study information, including name of the first author, year of the publication, country, study design, population, interventions, study settings, sample size, age (years), duration of diabetes (years), adherence measures (self-reported or instruments), response rate (%), proportion of non-adherence to anti-diabetic medication, and where available, odds ratio (ORs) with respective confidence intervals (CIs) for factors associated with adherence/non-adherence.