Facilitating Cross-National Comparisons of Indicators for Patient ...

DELSA/ELSA/WD/HTP(2008)1METHODOLOGICAL ISSUESIntroduction13. The methodology for facilitating internationally comparable Patient Safety Indicators set out inthis manual involves two key elements:• Cross-walk between the key disease classifications• Specified process of calculation14. The Patient Safety Indicators dealt with in this manual are specified according to certaindiagnosis and, in some instances, procedure codes. There are currently different medical classifications inuse for coding diagnosis; the ICD-9 (International Classification of Diseases) classification which is nolonger updated by the World Health Organisation (WHO) is the precursor of the present ICD-10classification. OECD member countries use ICD-9 (e.g. Spain, USA) as well as ICD-10 (e.g. Australia,Canada, Germany). For that reason this manual contains both versions of the coding system.15. Usually countries do not use the original version of a classification published by the WHO butmodify it according to their needs. Country modifications are still consistent with the WHO version,keeping the structure of the classification tree. In some chapters of the ICD classification the countryversions are more extensive than the WHO version while in others they are not. This manual does notcover all the different country versions of the ICD.16. The technical specifications of diagnosis in this manual are based on the ICD-10-WHO, 2006 andon the ICD-9-CM 3 . Therefore countries seeking to utilise this manual must ensure that before applying thedefinitions the defined codes for inclusion or exclusion criteria are currently in use. Otherwise thedefinitions at hand must be extended to include the subgroups added in the country modifications.17. For example, Table 2 shows that one three-digit WHO code for decubitus ulcer corresponds to 8four-digit codes in Canada, 5 four-digit codes in Australia and 50 five-digit German codes. To calculate thenumerator for the indicator decubitus ulcer, all country specific subgroups of the listed WHO code L89must be taken into account.3. Definitions in ICD-9-CM are adopted from AHRQ (2003).10