Validation of the Osteoporosis-Specific Morisky Medication Adherence Scale in long-term users of bisphosphonates

To examine the psychometric properties and validity of the 8-item Osteoporosis-Specific Morisky Medication Adherence Scale (OS-MMAS-8) in postmenopausal women prescribed bisphosphonates (BPs) for at least 15 months. A random sample of women aged a parts per thousand yen55 years with osteoporosis prescribed daily or weekly BPs was identified. Pharmacy fill data were extracted to calculate the medication possession ratio (MPR). Eligible women were stratified by low (< 0.50), medium (0.50-0.79), or high (a parts per thousand yen0.80) MPR, with the a priori goal of recruiting 133 participants in each group. OS-MMAS-8 scores can range from 0 to 8 and were categorized as low (< 6), medium (6 to < 8), and high (8) adherence. Internal consistency reliability (Cronbach's alpha), test-retest reliability [intraclass correlation coefficients (ICCs)] and convergent validity (correlating OS-MMAS-8 with MPR and other self-reported measures) were assessed. A total of 400 women out of 449 respondents reported that they were still taking their BPs at the time of the survey and completed OS-MMAS-8. Overall, 38.5, 34.3, and 27.3 % of participants had low, medium, and high OS-MMAS-8 scores, respectively. The mean (SD) MPRs according to OS-MMAS-8 scores (< 6, 6 to < 8 and 8) were 56.9 (22.6), 69.0 (24.9), and 76.7 (26.4), respectively. The correlation between OS-MMAS-8 and MPR was 0.36; p < 0.0001. Cronbach's alpha was 0.74, and the ICC was 0.83 (95 % CI 0.76-0.88). OS-MMAS-8 has acceptable psychometric properties for assessing medication adherence in postmenopausal women prescribed therapy for osteoporosis. Additional studies are needed to investigate the psychometric properties of OS-MMAS-8 in other settings and populations.