Reliability and validity of a modified 8-item Morisky Medication Adherence Scale in patients with chronic pain

The 8-item Morisky Medication Adherence Scale (MMAS-8) is a simple, economic and easy tool to evaluate the medication compliance of chronic disease. The reliability and validity of the MMAS-8 in patients with chronic pain were unclear. Therefore, we aimed to validate the MMAS-8 for detecting nonadherent patients with chronic pain.

A modified MMAS-8 was used to assess the medication compliance of patients with chronic pain who were treated at our hospital from July 2018 to October 2018. Cronbach's α was used to evaluate the internal consistency, and a factor analysis was used to examine the construct validity. Convergent validity was assessed by comparing the MMAS-8 and a medication adherence visual analog score (MA-VAS) through Pearson's correlation coefficient.

A total of 113 patients were evaluated. The (t-test) results revealed that there was a significant difference in average scores between the low-score group (who scored less than 5 points) and the high-score group (who scored 8 points or above), indicating that the scale displayed a good degree of discrimination. Except for Items 4 and 5, all the other items exhibited a good correlation with the total score (correlation coefficient >0.5; P<0.05). The Cronbach's α coefficient was 0.625, indicating that the scale's internal consistency was relatively satisfactory. Two common factors, which explained 62.978% of the total variance, were extracted by factor analysis to examine the construct validity of the MMAS-8, and the load of the 6 items was greater than 0.4. The Pearson correlation coefficient was 0.845 (P<0.001); thus, convergent validity was high.

The modified MMAS-8 exhibited acceptable reliability and validity in evaluating medication compliance in patients with chronic pain; thus, it can be applied to detect nonadherent patients with chronic pain.