Existing self-report tools are not suitable for measuring adherence to topical therapies in psoriasis (abstract only)

Adherence to topical therapies is poor in patients with psoriasis however the use of non-validated self-report tools in studies limits conclusions. Validated self-report tools such as the Medication Adherence Report Scale (MARS) are widely used to estimate adherence to oral medicines, however their validity for measuring adherence to topical therapies is unknown. Using in-depth cognitive interviews, the suitability of the MARS for measuring adherence to topical therapies was examined in 20 psoriasis patients recruited from UK community samples. Patients completed the MARS whilst simultaneously providing reasons for responses using a think-aloud technique. Data were coded and themes identified using content and framework analysis. As topical treatment prescription advice can vary more than oral medication, participants reported high levels of uncertainty about both quantity and frequency of treatment application. Patients made strategic judgements about their use of topical treatment which they had not discussed with clinicians. Strategies included either intentionally reducing or increasing the volume of medication used or the frequency of application, however this variable adherence was not reflected in the corresponding MARS scores. The thematic analysis of interview data identified the following influences on these behaviours: a) patients’ own beliefs about the cause of flares; b) perceived efficacy of topical therapies; and c) high levels of emotional distress. In its current form the MARS was unable to identify intentional non-adherence (neither over- or under-use of treatments). Given that most patients with psoriasis are managed with topical therapy and progression onto systemic therapy is largely determined by treatment response, a brief, valid and reliable tool for measuring adherence variability to topical treatments in both research and clinical settings is warranted.