title: Validity and reliability of chronic tic disorder and obsessive-compulsive disorder diagnoses in the Swedish National Patient Register.
abstract: OBJECTIVE
  The usefulness of cases diagnosed in administrative registers for research purposes is dependent on diagnostic validity. This study aimed to investigate the validity and inter-rater reliability of recorded diagnoses of tic disorders and obsessive-compulsive disorder (OCD) in the Swedish National Patient Register (NPR).
  
  
  METHODS
  Chart review of randomly selected register cases and controls.
  
  
  METHODS
  100 tic disorder cases and 100 OCD cases were randomly selected from the NPR based on codes from the International Classification of Diseases (ICD) 8th, 9th and 10th editions, together with 50 epilepsy and 50 depression control cases. The obtained psychiatric records were blindly assessed by 2 senior psychiatrists according to the criteria of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) and ICD-10.
  Positive predictive value (PPV; cases diagnosed correctly divided by the sum of true positives and false positives).
  
  
  RESULTS
  Between 1969 and 2009, the NPR included 7286 tic disorder and 24,757 OCD cases. The vast majority (91.3% of tic cases and 80.1% of OCD cases) are coded with the most recent ICD version (ICD-10). For tic disorders, the PPV was high across all ICD versions (PPV=89% in ICD-8, 86% in ICD-9 and 97% in ICD-10). For OCD, only ICD-10 codes had high validity (PPV=91-96%). None of the epilepsy or depression control cases were wrongly diagnosed as having tic disorders or OCD, respectively. Inter-rater reliability was outstanding for both tic disorders (κ=1) and OCD (κ=0.98).
  
  
  CONCLUSIONS
  The validity and reliability of ICD codes for tic disorders and OCD in the Swedish NPR is generally high. We propose simple algorithms to further increase the confidence in the validity of these codes for epidemiological research.
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Rück
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: K Johan
authors.initials: KJ
authors.lastname: Larsson
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lind
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ana
authors.initials: A
authors.lastname: Perez-Vigil
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Isomura
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Amir
authors.initials: A
authors.lastname: Sariaslan
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Mataix-Cols
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D015994:Incidence; D038801:International Classification of Diseases; D008297:Male; D015588:Observer Variation; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis* / Q000453:epidemiology; D012042:Registries; D015203:Reproducibility of Results; D013548:Sweden / Q000453:epidemiology; D013981:Tic Disorders / Q000175:diagnosis* / Q000453:epidemiology
keywords: Registries