title: How to interpret multidimensional quality of life questionnaires for patients with schizophrenia?
abstract: OBJECTIVE
  The classification of patients into distinct categories of quality of life (QoL) levels may be useful for clinicians to interpret QoL scores from multidimensional questionnaires. The aim of this study had been to define clusters of QoL levels from a specific multidimensional questionnaire (SQoL18) for patients with schizophrenia by using a new method of interpretable clustering and to test its validity regarding socio-demographic, clinical, and QoL information.
  
  
  METHODS
  In this multicentre cross-sectional study, patients with schizophrenia have been classified using a hierarchical top-down method called clustering using unsupervised binary trees (CUBT). A three-group structure has been employed to define QoL levels as "high", "moderate", or "low". Socio-demographic, clinical, and QoL data have been compared between the three clusters to ensure their clinical relevance.
  
  
  RESULTS
  A total of 514 patients have been analysed: 78 are classified as "low", 265 as "moderate", and 171 as "high". The clustering shows satisfactory statistical properties, including reproducibility (using bootstrap analysis) and discriminancy (using factor analysis). The three clusters consistently differentiate patients. As expected, individuals in the "high" QoL level cluster report the lowest scores on the Positive and Negative Syndrome Scale (p = 0.01) and the Calgary Depression Scale (p < 0.01), and the highest scores on the Global Assessment of Functioning (p < 0.03), the SF36 (p < 0.01), the EuroQol (p < 0.01), and the Quality of Life Inventory (p < 0.01).
  
  
  CONCLUSIONS
  Given the ease with which this method can be applied, classification using CUBT may be useful for facilitating the interpretation of QoL scores in clinical practice.
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France.|Department of Mathematics, Faculté des Sciences de Luminy, Aix-Marseille Univ, 13009, Marseille, France.
authors: Pierre
authors: P
authors: Michel
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France.
authors: Pascal
authors: P
authors: Auquier
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France.
authors: Karine
authors: K
authors: Baumstarck
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France.
authors: Anderson
authors: A
authors: Loundou
authors: Department of Mathematics, Faculté des Sciences de Luminy, Aix-Marseille Univ, 13009, Marseille, France.
authors: Badih
authors: B
authors: Ghattas
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France.
authors: Christophe
authors: C
authors: Lançon
authors: EA 3279 - Public Health, Chronic Diseases and Quality of Life - Research Unit, Aix-Marseille Univ, 13005, Marseille, France. laurent.boyer@ap-hm.fr.
authors: Laurent
authors: L
authors: Boyer
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011788:Quality of Life; D012559:Schizophrenia / Q000453:epidemiology*; D011795:Surveys and Questionnaires
keywords: Clustering; Quality of life; SF36; SQoL18; Schizophrenia; Unsupervised classification