Patient-reported outcome instruments that evaluate adherence behaviours in adults with asthma: a systematic review of measurement properties

AIM The aim of the present study was to identify systematically the measurement properties of patient-reported outcome instruments (PROs) that evaluate adherence to inhaled maintenance medication in adults with asthma. METHODS We conducted a systematic review of six databases. Two reviewers independently included studies on the measurement properties of PROs that evaluated adherence in asthmatic participants aged >= 18 years. Based on the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN), the reviewers: (i) extracted data on internal consistency, reliability, measurement error, content validity, structural validity, hypotheses testing, cross-cultural validity, criterion validity and responsiveness; (ii) assessed the methodological quality of the included studies; (iii) assessed the quality of the measurement properties (positive or negative); and (iv) summarized the level of evidence (limited, moderate or strong). RESULTS We screened 6068 records and included 15 studies (14 PROs). No studies evaluated measurement error or responsiveness. Based on methodological and measurement property quality assessments, we found limited positive evidence of: (i) internal consistency of the Adherence Questionnaire, Refined Medication Adherence Reason (MAR) scale, Medication Adherence Report Scale for Asthma (MARS-A) and Test of the Adherence to Inhalers (TAI); (ii) reliability of the TAI; and (iii) structural validity of the adherence questionnaire, MAR scale, MARS-A and TAI. We also found limited negative evidence of: (i) hypotheses testing of the Adherence Questionnaire; (ii) reliability of the MARS-A; and (iii) criterion validity of the MARS-A and TAI. CONCLUSIONS Our results highlighted the need to conduct further high-quality studies to evaluate the reliability, validity and responsiveness of the available PROs.