title: Usefulness of PHQ-9 in primary care to determine meaningful symptoms of low mood: a qualitative study.
abstract: BACKGROUND
  Self-administered questionnaires, such as the Patient Health Questionnaire (PHQ-9), are regularly used in clinical practice to guide prescribing or to measure recovery and response to treatment. There are concerns that patients are not all interpreting the questionnaire items in the same way. Cognitive interviewing is a research technique that identifies 'interpretative measurement error' (IME). IME is distinct from traditional components of measurement error, such as not reading the question as worded, or recording answers inaccurately.
  
  
  OBJECTIVE
  To use cognitive interviewing techniques to explore patterns in answer mapping and comprehension of the PHQ-9 questionnaire to ascertain whether the measure captures meaningful symptoms of low mood.
  
  
  METHODS
  Qualitative study using cognitive interviewing techniques and card sorting in six GP practices in Bristol.
  
  
  METHODS
  The study recruited 18 participants at the point of entry to a longitudinal primary care depression cohort study, PANDA (the indications for Prescribing ANtiDepressants that will leAd to a clinical benefit). Participants were interviewed 2, 4, and 6 weeks after their baseline visit. Cognitive interviews were digitally recorded. Analysis used the digital audio file, rather than verbatim transcripts, as it retained important features needed for analyses.
  
  
  RESULTS
  Cognitive interviewing revealed that items on the PHQ-9 are interpreted in a range of ways, that patients often cannot 'fit' their experience into the response options, and therefore often feel the questionnaire is misrepresenting their experience of meaningful symptoms of low mood.
  
  
  CONCLUSIONS
  The PHQ-9 may be missing the presence and/or intensity of certain symptoms that are meaningful to patients. Clinicians should adopt caution when using it.
authors.affiliation: Centre for Academic Primary Care, School of Social and Community Medicine;
authors.forename: Alice
authors.initials: A
authors.lastname: Malpass
authors.affiliation: Psychological Sciences, Institute of Psychology Health and Society;
authors.forename: Chris
authors.initials: C
authors.lastname: Dowrick
authors.affiliation: Professor of primary care mental health, Health Sciences, University of York, York.
authors.forename: Simon
authors.initials: S
authors.lastname: Gilbody
authors.affiliation: Professor of the anthropology of health and illness, head of the Department of Sociology, Social Policy and Criminology, School of Law and Social Justice, University of Liverpool, Liverpool.
authors.forename: Jude
authors.initials: J
authors.lastname: Robinson
authors.affiliation: Academic Unit of Psychiatry, Department of Community Based Medicine, University of Bristol, Bristol.
authors.forename: Nicola
authors.initials: N
authors.lastname: Wiles
authors.affiliation: Division of Psychiatry, UCL, London.
authors.forename: Larisa
authors.initials: L
authors.lastname: Duffy
authors.affiliation: Division of Psychiatry, UCL, London.
authors.forename: Glyn
authors.initials: G
authors.lastname: Lewis
mesh_terms: D000328:Adult; D003071:Cognition / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D011320:Primary Health Care / Q000379:methods*; D011594:Psychometrics / Q000379:methods*; D036301:Qualitative Research; D011795:Surveys and Questionnaires; D006113:United Kingdom / Q000453:epidemiology
keywords: PHQ-9; cognitive interviewing; depression; mood questionnaire; prescribing in primary care; safety culture
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