The goal
To allow continuous maintanance of ATC codes in NDMS and to allow their use in DRG assignment.

Background
Different NordDRG versions have used ATC-system to identify drugs both as componets of diagnostic information and as compoments of intervention information. 
For this purpose the the ATC information has been imported to the grouper either as secondary diagnosis code or as intervention code. 
Local systems have usually not been capable to handle 7 character codes as dx or procedure codes and therefore also the old NDMS was not designed to use more than 5 characters of the ATC ccodes.

However it is obvious that a major part of the information is lost when shortening the code to 5 characters. For this reason one has in Finland used for a number drugs the 5 last characters of the ATC code. This obviously looses the main part of the information, but for limited puposes this has worked. 
The new NDMS is now capable to handle as many characters as wanted 
At least in Finland THL has also started to collect 7 character ATC information and thus it seems possible to get full length ATC code information from the hospitals.

Because of the ongoing change we have not updated the ATC codes other than those that are actually used in NDMS and thus even the 5 character codes do not match with WHO Collaborating Centre for Drug Statistics Methodology (WHOCC) official classification. At least Sweden has expressed a need to update the ATC codes.

Our plan is now to implement all 5- and 7-charcter ATC codes to NDMS and I have donloaded the uptodate classification from WHOCC. The price of the download is 200€ and it seems that the national versions may not include the english text that is only available from WHOCC.

The comparison with finnish official version on the National code server revealed that a number of the national codes are not included in the up-to-date WHOCC version of ATC. The Finnish Medicines Agency (FIMEA) that is supposed to maintain the classification also on the code server has an almost perfectly updated version on their own web-site (only to WHOCC codes are missing).

Of the ATC codes that are included in the Swedish NordDRG definition tables quite many seem not to be included in the WHOCC ATC version. I have not checked for a complete ATC version from Sweden as I did not have readily available.

The problem seems to be that ATC system adds temporary codes that are later modified when 'correct' code is invented. WHOCC and FIMEA do not maintain history of the codes nor the mapping of old codes to current codes in the published versions of the system. The non matching national concepts usually exist in the WHOCC version but with another code.

An additional problem is that we have an almost complete Swedish translation of the WHOCC ATC codes form FIMEA, but the translations are different in Sweden and Finland.

In the future it might be optimal to maintain the ATC system as a separate basic classification that is used by both diagnostic and intervention components of the system.

Technical change 
We propose that all WHOCC 5- and 7-charcter codes are added to both procedure codes and Dx codes in NDMS. 
As diagnosis all ATC codes will belong to diagnosis category 00M00. This means that ATC codes cannot be used as principal diagnosis but some of them may have grouping properties (diagnosis properties) that affect DRG assignment. The properties that 5-character codes currently have will be given to all 7-character codes that are 'children' of the 5-character codes. 
As intervention codes the (used by Fin and Nor) the ATC codes will all have OR=0 property. They do not affect DRG assignment as surgical intervetions.They may have procedure properties (and grouping properties) and affect through these properties the assignment. When 7-character codes are added the properties are copied from existing codes to corresponding 7 character codes. 
As a second phase the 5-charcter codes will be omitted and the current codes will linked to the residuall group of the 7-chracter codes.

DRG change
The goal is that this change will not affect the DRG assignment at all. 
The countries may continue to use the existing codes as they will be linked wit codes with the current properties.