Abstract
Introduction: Rates of sub-optimal adherence to medications in asthma range up to 70%; the impact in severe asthma is likely to be particularly high. We measured self-reported adherence in participants in the U-BIOPRED cohort prescribed daily prednisolone using the Medication Adherence Response Scale (MARS), and compared to measured urinary prednisolone and metabolites in order to determine: 1. the prevalence of suboptimal adherence by each method; 2. the ability of MARS to predict urinary steroid detection.
Methods: Participants completed the MARS, and/or provided urine samples (analysed for prednisolone and metabolites by LCMS). The performance characteristics of the MARS predicting undetected urinary steroid were calculated in the subgroup having both tests.
Results: 181 participants currently taking regular oral corticosteroids were included, 59% female, mean (SD) age 54(12)yrs, FEV1 64.7(20.4)% predicted. Sub-optimal adherence (MARS score < 4.5) was reported in 62 participants, and 76 did not have detectable urinary prednisolone or metabolites. Good adherence by both methods was detected in only 52 participants (34%, see table). There was no difference in daily prednisolone dose between detectable and undetectable metabolites groups (p=0.848).
Conclusion: Low levels of adherence to treatment in severe asthma is a common problem, when measured either directly or self-reported. There was very poor agreement (48% concordance) between these two methods, and we suggest that, for now both approaches should be used.