Are your patients taking their medicine? Validation of a new adherence scale in patients with inflammatory bowel disease and comparison with physician perception of adherence

Abstract

Background: To date no adherence survey has been validated in IBD. The aim was to administer an improved medication adherence survey to IBD patients, to validate the scale in IBD, and to compare the results to perceived adherence by the gastroenterologists.

Methods: IBD patients were given the Morisky Medication Adherence Scale (MMAS-8). To validate the scale, prescription claim information, calculated as continuous single-interval medication availability (CSA) and mean possession ratio (MPR), was correlated to the MMAS-8 scale. Nonpersistence or low adherence was defined as a CSA or MPR<0.8. Treating gastroenterologists, blinded to the instrument, then assessed adherence in these patients.

Results: Of 110 IBD patients in the study, MMAS-8 identified 54 patients as low adherers (LAs) to their IBD medication and 56 patients as medium or high adherers (MHAs). Eighty-five percent of LAs had nonpersistent fill rates, as per CSA, compared with 11% of MHAs. Physicians correctly classified 95% of patients who were MHAs but only 33% of LAs. Underestimation of adherence only occurred in 5% of patients, whereas overestimation occurred in 67% (P<0.0001). In a linear regression analysis, CSA was significantly correlated with disease activity score (P<0.001).

Conclusions: LAs are a challenge to identify. This study demonstrates that the MMAS-8 scale is a valid instrument for assessing medication adherence in IBD. This is the first adherence scale to be validated in IBD.