Validity and reliability of chronic tic disorder and obsessive-compulsive disorder diagnoses in the Swedish National Patient Register

Abstract

ObjectivesThe 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).DesignChart review of randomly selected register cases and controls.Method100 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.Primary outcome measurementPositive predictive value (PPV; cases diagnosed correctly divided by the sum of true positives and false positives).ResultsBetween 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).ConclusionsThe 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.

Mortality risk in a nationwide cohort of individuals with tic disorders and with tourette syndrome

“…However, the results call for a cautious interpretation, given a few limitations of the study, such as the relatively small TS sample size and the rareness of the outcome, resulting in broad confidence intervals and precluding a more detailed examination of varying causes of death, and finally the diagnoses given in a clinical setting. A recent study in Sweden, however, showed that the validity and interrater reliability of tic disorders was high in a comparable registry . Finally, we only included persons with a diagnosis of tics derived in psychiatric and somatic hospitals and outpatient clinics, which generally convey a higher rate of mortality, than samples derived in settings of primary care …”

“…A recent study in Sweden, however, showed that the validity and interrater reliability of tic disorders was high in a comparable registry. 38 Finally, we only included persons with a diagnosis of tics derived in psychiatric and somatic hospitals and outpatient clinics, which generally convey a higher rate of mortality, than samples derived in settings of primary care. 9…”

Etiological overlap between obsessive‐compulsive disorder and anorexia nervosa: a longitudinal cohort, multigenerational family and twin study

“…The ICD‐10 codes had excellent validity, with a positive predictive value of 91% (rater 1) and 96% (rater 2). The inter‐rater agreement was outstanding (kappa=0.98, p<0.001) .…”

Patterns of Nonrandom Mating Within and Across 11 Major Psychiatric Disorders

“…This register has been heavily used in research, leading to standardized and validated protocols for selecting psychiatric populations. These protocols have been adhered to in the present investigation, with established codes (eMaterial in the Supplement) used to define cases of the following: schizophrenia, 19 bipolar disorder, 19 autism spectrum disorder (ASD), 19 anorexia nervosa, 19 substance abuse, 19 attention-deficit hyperactivity disorder (ADHD), 15 obsessive-compulsive disorder (OCD), 20 major depressive disorder (MDD), 19 social phobia, agoraphobia, 21 and generalized anxiety disorder (GAD). 21 Individuals with tic disorder were also selected, although small case numbers precluded examination of mating patterns in these populations.…”