Table 1 Outcome measures for medication adherence

 Hill-Bone high blood pressure compliance scale [20]

HB-HCT [20]

This scale uses a 14-item Likert scale to measure three behavioral domains a) reduced-sodium intake b) appointment keeping c) medication taking [20]. Cronbach’s alpha = 0.74 and 0.84.

 Self-structured questionnaires (ten items) [21]

SSQ-10 [21]

Researcher created tool which was validated with 23 respondents who served as the pilot study of this research [21]. Cronbach’s alpha value = 0.7.

 Morisky Medication Adherence Scale [22]

MMAS-8 [22]

MMAS-8 is a series of eight binary questions, a “No” is one point. A score of 8 indicates high adherence, 6–7 is medium, and < 6 is poor adherence [22]. Cronbach’s alpha = 0.83.

 11 Items adapted MMAS-8 [23]

Adapted MMAS-8 [23]

10- to 11-item questionnaire with scores ranging from 0 to 44. Adherent have scores, 0 to 21 and non-adherent scores, 22 to 44 [23]. Cronbach’s alpha = 0.932.

 Medical Outcomes Study Specific Adherence Scale [24]

MAOSS [24]

Assesses of participant’s tendency to adhere to eight behaviors associated with hypertension self-care that include patient’s ability to follow a salt and low fat or weight loss diet, take prescribed medications, cut down or stop smoking, curtail or avoid alcohol, exercise regularly, avoid stress, and use relaxation techniques for the past 4 weeks measured using a 6-point Likert scale. The higher the mean score, the greater the adherence [24]. Cronbach’s alpha = 0.811.

 Binary adherence question

Binary [25]

Is the respondents taking the right medications at the right dosages at the right time, answerable by yes or no [25].

 Medication Adherence Questionnaire [26]

MAQ [26]

A total score of 0–1 was defined as adherent while 2 or above was considered as non-adherent [26].

 Adherence Self-Report Questionnaire [27]

ASRQ [27]

A brief self-administered questionnaire measuring “timing adherence,” defined as taking medications at the correct dose and intervals. Has six items describing adherence to the timing of medication intake. Adherence was defined as an ASRQ score of less than or equal to 2 [27]. Specificity 90.3% and sensitivity 14.6%.

 Proportion of days covered

PDC [14]

Days the patient was covered by at least one drug for each type of medication, based on the prescription fill date and days of supply divided by the number of days of drug coverage and multiplied by 100. Medication adherence was defined using the standard threshold of PCD greater than 80% [14]. Data on filled medications including medication names, fills and days of supply were obtained from pharmacy claims databases [14].

 Medication Possession ratio

MPR [28]

Calculated by dividing the no of day supply dispensed by the no of days evaluated multiplied by 100%. For the research they used the formula Possession ratio = days supplied for 1stRX/(filldateof2ndRX-filldateof1stRX). Possession ratio of 0.8 or greater was considered adherent [16, 28]