Validation of the Identification of Medication Adherence Barriers Questionnaire (IMAB-Q); a Behavioural Science-Underpinned Tool for Identifying Non-Adherence and Diagnosing an Individual's Barriers to Adherence.

Purpose: To validate the Identification of Medication Adherence Barriers Questionnaire (IMAB-Q) as a tool to guide practitioners to identify patients who require support to take their medicines as prescribed, their key barriers to adherence and select relevant behaviour change techniques. Patients and Methods: Adults prescribed medication for cardiovascular disease prevention were recruited from nine community pharmacies in England. Participants completed the IMAB-Q comprising 30 items representing potential barriers to adherence developed from our previous mixed methods study (scoping review and focus groups) underpinned by the Theoretical Domains Framework. Participants also self-reported their adherence on a visual analogue scale (VAS) ranging from perfect adherence (100) to non-adherence (1). A subgroup of 30 participants completed the IMAB-Q twice to investigate test-retest reliability using weighted Kappa. Mokken scaling was used to investigate IMAB-Q structure. Spearman correlation was used to investigate IMAB-Q criterion validity compared to the VAS score. Results: From 1407 invitations, 608 valid responses were received. Respondents had a mean (SD) age of 70.12 (9.9) years and were prescribed a median (IQ) 4 (3, 6) medicines. Worry about unwanted effects (n = 212, 34.5%) and negative emotions evoked by medicine taking (n = 99, 16.1%) were most frequently reported. Mokken scaling did not organise related IMAB-Q items according to the TDF domains (scalability coefficient H = 0.3 to 0.6). Lower VAS self-reported adherence correlated with greater IMAB-Q reported barriers (rho = -0.14, p = 0.001). Test-retest reliability of IMAB-Q items ranged from kappa co-efficient 0.9 to 0.3 (p < 0.05). Conclusion: The IMAB-Q is valid and reliable for identifying people not adhering and their barriers to adherence. Each IMAB-Q item is linked to a TDF domain which in turn is linked to relevant behaviour change techniques. The IMAB-Q can therefore guide patients and practitioners to select strategies tailored to a patient's identified barriers.