To validate the diagnosis of hyperkinetic disorders (HD) in the Danish Psychiatric Central Research Registry (DPCRR) for children and adolescents aged 4 to 15 given in the years 1995 to 2005.

From a total of 4568 participants, a representative random subsample of n = 387 patients were used to validate the diagnosis. Patient files were systematically scored for the presence of ICD-10 criteria for HD and oppositional defiant disorder/conduct disorder (ODD/CD; F91). Further to this, an inter-rater reliability study was also conducted, whereby two experienced child and adolescent psychiatrists who were blind to patients discharge diagnoses, rated a random subsample of n = 101 participants.

Information was available for 372 out of 387 patients. Out of n = 372 available files, n = 324 (86.8%) were evaluated to fulfil diagnostic criteria for HD. Due to missing information it was not possible to reach a conclusion for 5.1% of the cases, 3.8% of the diagnoses were registration errors, and in 4.3% of the files the diagnosis had to be rejected. Inter-rater agreement was high (κ = 0.83, z = 10.9, P < .001). The validity of hyperkinetic disorders, unspecified (F90.9) was lower and comorbid CD/ODD were under-diagnosed in the sample. All participants fulfilling HD criteria also fulfilled DSM-5-criteria for ADHD.

The risk of misclassification of patients with HD in the DPCRR is relatively low, with the exception of the diagnosis of hyperkinetic disorders, unspecified (F90.9).