The Health of the Nation Outcome Scales (HoNOS) comprises 12 scales that cover the kinds of problems that may be experienced by working-age adults in contact with specialised mental health services. Drawing on 20 years' experience in clinical practice, a collaborative, international review of the HoNOS was undertaken and a revised measure (known as the HoNOS 2018) was published. In this study, 32 experts from Australia, England and New Zealand completed an anonymous web-based survey to assess the relevance, comprehensiveness and comprehensibility (aspects of content validity) of the HoNOS 2018. The experts rated 11 of the 12 HoNOS 2018 scales as 'important' or 'very important' for determining the overall clinical severity (item-level content validity index or I-CVI ≥ 0.75). Evaluations of the scales' ability to capture change, comprehensiveness and comprehensibility were more variable, but generally positive. Experts' comments provided further insights into this variability; for example, they noted that some scales combine multiple phenomena, which can result in ambiguity in item wording and assessment challenges. Results from this study suggest that the revisions have not altered the importance of the scales. Given the measure's breadth of content, training remains important for ensuring rating fidelity. Inter-rater reliability and utility testing are indicated.
Keywords: content validity; measurement properties; mental health services; routine outcome measurement.