CONVERSION PROBLEMS CONCERNING AUTOMATED MAPPING FROM ICD-10 TO ICD-9

The increasing parallel use of ICD-9 and ICD-10 complicates the compar ability of coded diagnoses. This is the reason why we developed a symm etric table for interactive conversion between ICD-9 and CD-10, based on a vector space text-retrieval method that resulted in unambiguous m apping from ICD-9 to ICD-10 in 64%, from ICD-10 to ICD-9 in 87%, of al l three- and four-character classes of the tabular list. Out of the re maining 13% of multi-valued relations, a table for automated mapping f rom ICD-10 to ICD-9 was created. In 9% of cases, the selection offered no problems. A compromise between preserving information content and maintain ng the logical integrity had to be found in 2.4%; in 1.6% aut omated mapping was impossible because of newly defined concepts and st ructural differences between ICD-9 and ICD-10 that are not counterbala nced by a consistent system of residual categories. We recommend that in a future revision of the ICD, compatibility with the then existing classification system should be considered.