At CRA 2016, Raquel Sweezie presented an analysis of the reliability of two short medication adherence questionnaires in patients with rheumatoid arthritis.
Adherence is defined as the extent to which a patient takes a medication as prescribed by their health care provider. In rheumatology, adherence rates have been reported to be as low as 30%. The most commonly used questionnaire to assess adherence in rheumatology is the19-item Compliance Questionnaire Rheumatology (CQR-19).
Recently, two shorter questionnaires have been developed including a 5-item Compliance Questionnaire Rheumatology (CQR-5) and the 9-item Medication Adherence Rating Scale (MARS-9).
The reliability analysis was conducted in a group of randomly selected patients with rheumatoid arthritis (RA) from a group of patients at Sunnybrook Hospital in Toronto. The researches recruited 100 patients, with a mean age of 61, the vast majority were female, and the patients were highly educated with 78% having at least some post-secondary education.
The CQR-5 and MARS-9 medication adherence questionnaires were administered to the group. The questionnaires were completed at three time points: at baseline, 2 weeks, and 3 months.
Between baseline and the 2-week visit, the Intra-Class Correlation Coefficient (ICC) for the CQR-5 was 0.78. This is considered to be an acceptable ICC. Between baseline and 3 months, the ICC was fairly stable at 0.73. Interestingly, this ICC was identical to the data published for the original CQR-19. This suggests the CQR-5 is stable over time.
The ICC for the MARS-9 was 0.57 measured between baseline and 2 weeks, and 0.43 between baseline and 3 months.
In summary, the CQR-5 appears to be more reliable than the MARS-9 as measured by the ICC. Furthermore, test-retest reliability of the CQR-5 was similar to the original CQR-19.
Challenges with medication compliance questionnaires remain prevalent. Medication compliance questionnaire scores have been positively correlated with semi-structured interviews. However, questionnaires and interviews do not correlate well with electronic medication measures or with medication possession ratios (MPRs). Medication compliance questionnaires likely under-report the true level of adherence. If in doubt about a patient's adherence, call the pharmacy. It isn't perfect but it is the best we have.