Content Validity and Reliability of a Self-Report Measure of Medication Nonadherence in Hepatitis C Treatment
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Nonadherence to direct-acting agents (DAAs) for hepatitis C (HCV) decreases viral response. To measure nonadherence to DAAs, a reliable, valid, and easily implemented method is needed.
The goals of this study were to refine a previously validated (in patients with hypertension) self-report measure of extent of nonadherence and reasons for nonadherence in the context of DAAs and to obtain initial evidence of content validity and reliability.
Phase I involved two focus groups with patients with HCV (n = 12) and one focus group with prescribers of HCV medications (n = 6) to establish content validity of reasons for nonadherence. Subsequent cognitive interviews with patients (n = 11) were conducted to refine items. Phase II was a prospective cohort study involving weekly administration of the refined measure by telephone to patients (n = 75) who are prescribed DAAs to evaluate reliability and consistency with viral response.
In the cohort study, internal consistency ranged from acceptable (α = .69) to very high (α = 1.00) across time points and was quite high on average (α = .91). Across the 75 participants, there were 895 measurement occasions; of those, nonadherence was reported on only 27 occasions (3%), all of which occurred in the first 12 weeks. These 27 occasions represented 19 (26%) different individuals. At 12 weeks, 1 (1%) of patients had a detectable HCV viral load; at 12–24 weeks posttreatment, 4 (5%) had a sustained viral response. Nonadherent patients reported an average of 1.41 reasons for nonadherence.
This multi-method study established content validity of reasons for nonadherence and reliability of extent of nonadherence. High rates of adherence and viral response were consistent with previous studies using other nonadherence measurement methods.
KeywordsAdherence Content validity Cognitive interviews Focus groups Qualitative research Psychometrics
The authors would like to extend special thanks to Andrew Muir, MD MHS, and Christine Hunt, MD, for their clinical input and Jamiyla Bolton, Jahdai Dawes, Leslie Gaillard, Tina Lucas, Elizabeth Strawbridge, and Cherisa Williams for their assistance with recruitment and data collection. The views represented in this article represent those of the authors and not those of the VA or the United States Government.
Phase I of this study was supported by an investigator-initiated grant from Vertex Pharmaceuticals to Dr. Voils. Phase II of this study was funded by the Department of Medicine at Duke University Medical Center. Effort on this paper was supported by resources and facilities at the Veterans Affairs Medical Centers in Madison and Durham and by a Research Career Scientist award to Dr. Voils from the Health Services Research and Development (HSR&D) service of the Department of Veterans Affairs (VA; RCS 14-443) and a VA HSR&D Career Development Award to Dr. Gellad (CDA 14-158).
Compliance with ethical standards
Conflict of interest
Dr. Gellad is cofounder and holds equity in Higgs Boson Inc. No other author declares a conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
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