Discussion
For Norway as a whole, the prevalence of autism spectrum disorders, ADHD, epilepsy and cerebral palsy was in line with our previous estimates (3). There are significant differences across counties with regard to autism spectrum disorders and ADHD – to an extent that can hardly be explained by way of underlying real variations in prevalence. Our findings indicate that considerable regional variations in diagnostic and/or coding practices have developed. If so, this will concur with the differences across counties that have been demonstrated for treatment practice regarding ADHD, with large variations in the proportion of inhabitants provided with anti-ADHD drugs (5). The medical profession will have a large interest in obtaining more knowledge about the causes of these regional variations. In light of current figures, we may question whether children with autism spectrum disorders and ADHD are provided with uniform and equal health services in Norway.
As regards epilepsy and cerebral palsy, the geographical variations in prevalence are relatively minor. Most likely, this is because diagnostics of such conditions leave less room for discretionary judgement, but we would not exclude the potential importance of the fact that the diagnostic responsibility is concentrated in a considerably smaller number of institutions than is the case for diagnostics of autism spectrum disorders and ADHD.
The lack of data from private contract specialists may have caused a certain underestimation of the prevalence of ADHD. Overviews of consultations reported for social security reimbursements show that 5 – 10 % of all ADHD diagnoses are registered by private contract specialists. Many of these patients will be registered in public health institutions as well, but we have no knowledge of the potential degree of overlap. Children with autism spectrum disorders, epilepsy and cerebral palsy are almost exclusively diagnosed and followed up in public health institutions, and the dearth of data from private contract specialists will have had only little effect on the prevalence data for these conditions.
Many of the health enterprises, including Oslo University Hospital, report disease codes from the enterprise as a whole, without any specification of institutions. This is a weakness of the reporting practice, since health enterprises mostly consist of several units in various locations and with varying traditions for diagnostics and treatment. The value of this reporting would increase if the individual institutions were specified for each health enterprise.
Norwegian specialist health services for children are strongly decentralised. Our count shows that the four conditions we have studied here were registered in 20 somatic hospitals and 102 psychiatric units in 2011. As a result of this decentralisation, many institutions treat a very small number of children in each diagnostic group. The quality of the diagnostics and treatment provided for these four conditions has not been investigated, but we believe that there is reason to ask whether the current dispersion of specialist competence over so many institutions really is an advantage with regard to the patients.
The geographical and physical separation of paediatrics from the psychiatric services for children and youth is also a source of wonderment to us. Neurological and psychiatric afflictions in children often result in complex disease pictures, making cooperation across specialities and professions essential. Being aware of the comprehensive overlap that may occur between various conditions and of the neurobiological basis of many of these disorders, this strict separation of paediatrics from the psychiatric services for children and youth appears artificial as well as outdated.
For many children with autism spectrum disorders, ADHD and epilepsy, the conditions cannot be found in the Norwegian Patient Register every year. In some cases this may be due to coding practice, but it remains obvious that a large number of these children are not provided with consistent follow-up by the specialist health services. We assume that they are followed up by GPs and the educational and psychological counselling services at the municipal level. For children with ADHD, this is in line with the guidelines for diagnostics and treatment issued by the Norwegian Directorate of Health (6). We believe that it would be interesting to investigate whether this follow-up is of sufficient quality when undertaken only under the auspices of the educational and psychological counselling services and the municipal healthcare services. These services are even more decentralised than the specialist health services, and the number of children correspondingly smaller. No registry data are currently available from the educational and psychological counselling services or the primary health services to provide the kind of information on the specialist health services collected by the Norwegian Patient Register.
A national register facilitates investigation of the prevalence of diseases with de-identified data files and a minimum of resource use. A national register also permits comparisons of prevalence across counties and institutions. This would be impossible if the reporting had been made voluntary and based on consent.