title: QUINT: A tool to detect qualitative treatment-subgroup interactions in randomized controlled trials.
abstract: The detection of subgroups involved in qualitative treatment-subgroup interactions (i.e., for one subgroup of clients treatment A outperforms treatment B, whereas for another the reverse holds true) is crucial for personalized health. In typical Randomized Controlled Trials (RCTs), the combination of a lack of a priori hypotheses and a large number of possible moderators leaves current methods insufficient to detect subgroups involved in such interactions. A recently developed method, QUalitative INteraction Trees (QUINT), offers a solution. However, the paper in which QUINT has been introduced is not easily accessible for non-methodologists. In this paper, we want to review the conceptual basis of QUINT in a nontechnical way, and illustrate its relevance for psychological applications.
  
  
  
  We present a concise introduction into QUINT along with a summary of available evidence on its performance. Subsequently, we subject RCT data on the effect of motivational interviewing in a treatment for substance abuse disorders to a reanalysis with QUINT. As outcome variables, we focus on measures of retention and substance use.
  
  
  
  A qualitative treatment-subgroup interaction is found for retention. By contrast, no qualitative interaction is detected for substance use.
  
  
  
  QUINT may lead to insightful and well-interpretable results with straightforward implications for personalized treatment assignment.
authors.affiliation: a Department of Psychology and Educational Sciences , Katholieke Universiteit Leuven , Leuven , Belgium.
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Doove
authors.affiliation: a Department of Psychology and Educational Sciences , Katholieke Universiteit Leuven , Leuven , Belgium.|b Department of Methodology and Statistics , Tilburg University , Tilburg , The Netherlands.
authors.forename: Katrijn
authors.initials: K
authors.lastname: Van Deun
authors.affiliation: a Department of Psychology and Educational Sciences , Katholieke Universiteit Leuven , Leuven , Belgium.|c Mathematical Institute, Leiden University , Leiden , The Netherlands.
authors.forename: Elise
authors.initials: E
authors.lastname: Dusseldorp
authors.affiliation: a Department of Psychology and Educational Sciences , Katholieke Universiteit Leuven , Leuven , Belgium.
authors.forename: Iven
authors.initials: I
authors.lastname: Van Mechelen
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D006801:Humans; D062405:Motivational Interviewing / Q000379:methods; D017063:Outcome Assessment, Health Care / Q000379:methods*; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D019966:Substance-Related Disorders / Q000628:therapy
keywords: QUINT; qualitative interaction; subgroup analysis; treatment efficacy