Background 

Poor adherence to the lifelong vitamin and mineral supplementation post bariatric surgery is common and can be a challenge for healthcare professionals to recognize. There are several questionnaires for self-reporting of adherence to chronic medication, but none has been evaluated for assessment of adherence to vitamin and mineral supplementation post bariatric surgery.

Aim: 

To assess the accuracy of the 5-item Medication Adherence Report Scale (MARS-5) in measuring adherence to vitamin and mineral supplementation post bariatric surgery. 

Method: 

We validated the psychometric properties of MARS-5 for vitamin and mineral supplementation in two cohorts: one at 1 year post bariatric surgery (n=120) and one at 2 years post-surgery (n=211). The validity was compared to pharmacy refill data for vitamin B12 and combined Calcium/vitamin D as reference.

Results: 

Correlation analyzes demonstrated that the MARS-5 demonstrated acceptable validity compared to objectively measured adherence rate from pharmacy refill data calculated as continuous, multiple-interval measures of medication availability/gaps (coefficient ranged from 0.49 to 0.54). Internal reliability (Cronbach's α) was high: 0.81 and 0.95, respectively.  A ceiling effect was seen, where one out of three scored max in MARS-5.

Conclusion: 

MARS-5 demonstrated acceptable, but not optimal, psychometric properties for assessment of adherence to vitamin and mineral supplementation post bariatric surgery. We encourage further validation of other questionnaires for assessing adherence of vitamin and mineral supplementation post bariatric surgery.