Exploring the relationship between health knowledge, health literacy, self-care, self-efficacy, and glycemic control among adults with type 2 diabetes mellitus

Table 1 Description and psychometrics of study questionnaires[23-37]

Number	Domain	Description	Psychometrics
1	Sociodemographic and clinical data	24 items, e.g., age, gender, ethnicity, blood pressure, body weight, diabetes complications, etc	Not applicable
2	Laboratory data	8 specific laboratory test results, e.g. fasting glucose, fasting lipids, HbA1c	Not applicable
3	Self-care	There are several versions of Summary of Diabetes Self-care Activities scale. It was developed by Toobert et al[23]. The self-care activities of patients with diabetes included diet, physical activity, blood glucose self-monitoring, foot care, smoking, and medication adherence. The 10-item version (excluding smoking and medication adherence) was validated in Malaysia by Bujang et al[24]. The version used in this study had 11 items (five diet items instead of four)	Cronbach’s α of subscales varied between 0.651 and 0.905 as reported by Bujang et al[24] (based on 10-item version)
4	Self-efficacy	Diabetes Management Self Efficacy Scale-15, a 15-item scale measuring the confidence of respondents in their ability to carry out actions that promote diabetes management. It has been validated in the United Kingdom by Sturt et al[25]. This scale was a shortened version of the original 20-item version developed by Bijl et al[26]	No prior validation had been published from Malaysia
5	Health knowledge	Michigan Diabetes Knowledge Test-14 was developed by Fitzgerald et al[27]. Some versions include another 9 items on insulin use (these were not included in this study). Threshold of adequate diabetes knowledge is a score ≥ 7	Cronbach’s α = 0.702 as reported by Al-Qazaz et al[28]
6	Health literacy	Health literacy is the ability to access, read, understand, and use health information to make appropriate healthcare decisions and follow instructions for treatment. Malaysian version of Health Literacy Survey is a shorter 18-item version developed from the European Health Literacy Survey[29]. Threshold for limited health literacy was set at transformed health literacy score ≤ 33 (hence, sufficient or excellent level is > 33)	Cronbach’s α = 0.906 as reported by Mohamad et al[30]
7	Medication adherence	Malaysia Medication Adherence Assessment Tool is a 12-item scale developed by Hatah et al[31]. Score ≥ 54 was considered as adherence	Cronbach’s α = 0.910 as reported by Hatah et al[31]
8	Diabetes distress	Diabetes Distress Scale is a 17-item scale assessing diabetes-related emotional distress. It was developed by Polonsky et al[32]. A mean item score of ≥ 3 was considered a level of distress worthy of clinical attention. Four subscales can be computed (emotional burden, physician distress, regimen distress, and interpersonal distress)[33]	Cronbach’s α for Malay version is 0.94 as reported by Chew et al[34]. Cronbach’s α for English version is 0.92 as reported by Chin et al[35]
9	Depression	Patient health questionnaire is a 9-item scale (PHQ-9) based on the diagnostic and statistical manual of mental disorders IV that aims to measure the level of depression. It was developed by Kroenke et al[36]. PHQ-9 score ≥ 10 was indicative of moderate levels of depression. Major depression can be diagnosed if the following criteria are satisfied: (1) Item 1 or item 2 scores ≥ 2; and (2) Five items with the following scoring: Items 1-8 scores ≥ 2 or item 9 score ≥ 1	Cronbach’s α = 0.67 as reported by N Azah et al[37]

HbA1c: Glycated hemoglobin.