cor984
by Conrad Warnke
9/7/07

Cause of death and disability coded were originally coded using the International 
Classification of Dieases 9th Edition Clinical Modification (ICD-9-CM-A) and 
International Classification of Functioning (ICF) for 2003-2007 interviews. In mid 
2007 the WLS decided to create ICD-10-AM versions of these variables.  This was done
more so to preempt demand from researchers as well as NDI's usage of ICD-10 for
deaths 1999 and beyond.

Instead of going back and doing ICD-10 codes from the original responses two ICD-9
to ICD-10 maps were found.  New Zealand Health and Information Service offers a map
but it seems incomplete and there are creditability issues. The National Centre for 
Classification in Health (NCCH) offers a detailed and complete map.  The NCCH 
creates, maintains, publishes and distributes the classification under licence from 
the World Health Organization which owns and develops ICD-10 so their mapping seems
very reliable (http://www3.fhs.usyd.edu.au/ncch/1.9.htm#syd).

There was some trickness to the map because the WLS version of ICD-9 is slightly 
different since WLS only has intergers and the map has decimals. This potentially
could cause an improper ICD-10 recode, for example:

ICD-9   ICD-10
848.5   S33.7 
848.8   T14.3 
848.9   T14.3

For mapping I use the icd-9 codes that end in .9, if available, as a quick and 
reasonable way of choose the 'best' match for WLS since the .9  are always the
unspecified. A great majority of the time the respondent is not very detailed so the
WLS code would be the unspecified code (it would end in .9 if WLS went to the tenths
place). So the mapping program takes the .9 map where available, otherwise it take
the first one listed. 72% of the ICD-9 codes in the WLS mapping end in .9 and 13%
are the only code for that integer.

At this time there is no reliable map for the ICD-9 Volume 3 codes.  The ICD-10 
equivalent does exist - ICD-10-PCS, but it's either in the draft stage or is largely
unused at this point. Either way, at this point it did not make sense to map these 
codes.  These are coded -2 for inappropriate in the ICD-10 analysis variables. Also,
since there is no direct mapping between ICF and ICD-10 these are also coded 
inappropriate in the new ICD-10 analysis variables.

Other relevent documents
	cor984a - complete list of ICD-10 codes
        cor984b - original ICD-9 to ICD-10 mapping
        cor984c - WLS ICD-9 to ICD-10 mapping
        cor984d - Excel list of ICD-9 and ICD-10 vars