Abstract
Background: The application of measurement science in early intervention mental health is in its infancy, with a lack of youth-centred and culturally specific measures. Kessler’s Distress Scale (K10) is widely recommended to evaluate youth mental health services internationally, even though its suitability has been assessed incompletely. Our aim was to examine the K10’s fitness for purpose as an outcome measure for evaluating integrated care services for youth age 12-24 years.
Method: We conducted a qualitative study evaluating the K10’s development against current recommendations for developing patient reported outcomes (PROs) measures. We also conducted a quantitative study examining the K10’s measurement properties, using two psychometric methods, in data from 7360 youth accessing services at nine Canadian youth mental health centres.
Results: Our qualitative study concluded K10’s development did not meet requirements for measurement. Specifically, the concept for measurement was neither defined nor conceptualised and items were selected statistically. In stark contrast, our quantitative study [mean age 18.5 years (SD = 2.9), 65% female] concluded K10 is “reliable and valid”.
Conclusion: K10’s “validity” in a quantitative but not qualitative sense means K10 measures something, but it is unclear what that something is, resulting in a weak scientific basis for developing and evaluating youth mental health services. This measurement paradox arises because K10’s items were selected statistically. Our study highlights the fundamental requirement for scales used in integrated care environments to have strong conceptual bases, the misleading nature of quantitative psychometric evaluations developed without qualitative examinations, and the urgent need for integrated care services to have new fit-for-purpose patient-reported outcomes co-designed by youth and fit for purpose to improve the outcomes and experiences of youth.