Presentation and validation of the Abbreviated Self Completion Teen-Addiction Severity Index (ASC T-ASI): A preference-based measure for use in health-economic evaluations.

Economic evaluations of new youth mental health interventions require preference-based outcome measures that capture the broad benefits these interventions can have for adolescents. The Abbreviated Self Completion Teen-Addiction Severity Index (ASC T-ASI) was developed to meet the need for such a broader measure. It assesses self reported problems in seven important domains of adolescents' lives, including school performance and family relationships, and is intended for use in economic evaluations of relevant interventions. The aim of the current study was to present the ASC T-ASI and examine its validity as well as its ability to distinguish between adolescents with and without problems associated with substance use and delinquency. The validation study was conducted in a sample of adolescents (n = 167) aged 12-18 years, who received in- or outpatient care in a youth mental health and (enclosed) care facility in the Netherlands. To examine its feasibility, test-retest reliability, and convergent validity, respondents completed the ASC T-ASI, as well as the EQ-5D-3L and SDQ at baseline and after a two-week interval using a counterbalanced method. The ASC T-ASI descriptive system comprises seven domains: substance use, school, work, family, social relationships, justice, and mental health, each expressing self reported problems on a five-point Likert scale (ranging from having 'no problem' to having a 'very large problem'). The majority of respondents (>70%) completed the ASC T-ASI within 10 minutes and appraised the questions as (very) easy and (very) comprehensible. Test-retest reliability was adequate (Kw values 0.26-0.55). Correlations with the supplementary measures were moderate to high (rs 0.30-0.50), suggesting convergent validity. The ASC T-ASI is a promising and valid measure for assessing self reported problems in important domains in adolescents' lives, allowing benefits beyond health and health-related quality of life to be included in economic evaluations of youth mental health interventions. Future studies of the ASC T-ASI should consider the comprehensiveness of its domains and sensitivity to change.