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.