The comparability over time is good.
In certain areas, however, we must pay attention: - Transition from diagnosis classification ICD08 to ICD10 in 1994 - Outpatient treatments and emergency room visits included from 2006 - Data break between 2013 and 2014 for outpatient treatments and emergency room visits. - Structural reform 2007, redivision of local government - Income replacing benefits not included after 2007
Eurostat and the OECD make comparable data collections and publications in this field. There are a number of organisational and institutional conditions that we must keep in mind when comparing countries.
In other – especially European – countries, registers exist of the same type as the Danish National Hospital Discharge Register. The coding on diagnoses will typically be by international classification. For international comparison, it is recommended that you look at data from Eurostat and the OECD which make comparable data collections and publish data that are comparable to a certain extent in this field. There are a number of organisational and institutional conditions that we must keep in mind when analysing any differences.
The statistics have been compiled on the same basis from the beginning in 1990.
As at 1 January 1994, the new classification of diseases (ICD10) was employed in Denmark. This replaced the former ICD8 classification. This means that we must be cautious when comparing the diagnosis pattern across this point in time. The development in the diagnosis pattern can further be influenced by changes in the registration practice. E.g. the number of admissions with diagnoses in the group Symptoms and insufficiently defined states has increased significantly. This is due to an enhanced tendency to register symptoms and less use of actual disease diagnoses in the examination phase or in case of uncertainty as to the nature of the disease. Consequently, the number of admissions e.g. with diagnoses in the group Tumours has declined. The National Hospital Discharge Register’s data about admissions caused by road traffic accidents is estimated to be insufficient up to and including 1994. From 1995, the data is considered to be sufficient.
In an evaluation of the hospitalisation rate for the years 1995 and 2008 respectively, nurse disputes in these years must be taken into consideration.
In an evaluation of the number of outpatient treatments and the number of emergency room visits, a data break between 2013 and 2014 must be taken into consideration. There may be a related effect of the data break in 2015, especially in the Capital Region of Denmark.
The statistics’ use of background information has continuously been extended. Accordingly, it will not be possible to retrieve certain statements for all years back in time.
The Danish Health Data Agency (previously SSI and the Danish Health Authority respectively) publish information in eSundhed (eHealth) from the National Hospital Discharge Register, moreover, they publish key figures for the health sector on a quarterly basis. Deviations in key figures on the number of admissions and outpatient treatments are due to the fact that the Danish Health Data Agency makes publications based on non-cleansed versions of the National Hospital Discharge Register or based on “Det Grupperede Landspatientregister” (the Grouped National Hospital Discharge Register), where DRG is included. Furthermore, there may also be differences in the delimitation, e.g. inclusion of publicly financed treatments in private hospitals in the Danish Health Data Agency’s key figures. The development from one period to the next is generally consistent between the Hospitalisation rate and Key figures from the Danish Health Data Agency.
The Danish Health Authority published an annual set of statistics until 2005 – also based on the National Hospital Discharge Register – about the activity in the hospitals (Hospital Statistics). The hospitalisation rate is comparable to these statistics, except from the fact that the hospitalisation rate in most statements only include persons who were in the population as at 1 January (and consequently not persons born or immigrated during the year) and that the hospitalisation statistics in the geographical statements group the persons with their residence as at 1 January, whereas the Danish Health Authority’s statements in the Statistics relating to hospitals group the persons with their municipality of residence at the time of admission.
Data are internally consistent.