TY - JOUR

T1 - A unidirectional mapping of ICD-8 to ICD-10 codes, for harmonized longitudinal analysis of diseases

AU - Pedersen, Mette Krogh

AU - Eriksson, Robert

AU - Reguant, Roc

AU - Collin, Catherine

AU - Pedersen, Helle Krogh

AU - Sørup, Freja Karuna Hemmingsen

AU - Simon, Christian

AU - Birch, Anna Marie

AU - Larsen, Michael

AU - Nielsen, Anna Pors

AU - Belling, Kirstine

AU - Brunak, Søren

N1 - Publisher Copyright: © 2023, The Author(s).

PY - 2023

Y1 - 2023

N2 - Periodic revisions of the international classification of diseases (ICD) ensure that the classification reflects new practices and knowledge; however, this complicates retrospective research as diagnoses are coded in different versions. For longitudinal disease trajectory studies, a crosswalk is an essential tool and a comprehensive mapping between ICD-8 and ICD-10 has until now been lacking. In this study, we map all ICD-8 morbidity codes to ICD-10 in the expanded Danish ICD version. We mapped ICD-8 codes to ICD-10, using a many-to-one system inspired by general equivalence mappings such that each ICD-8 code maps to a single ICD-10 code. Each ICD-8 code was manually and unidirectionally mapped to a single ICD-10 code based on medical setting and context. Each match was assigned a score (1 of 4 levels) reflecting the quality of the match and, if applicable, a “flag” signalling choices made in the mapping. We provide the first complete mapping of the 8596 ICD-8 morbidity codes to ICD-10 codes. All Danish ICD-8 codes representing diseases were mapped and 5106 (59.4%) achieved the highest consistency score. Only 334 (3.9%) of the ICD-8 codes received the lowest mapping consistency score. The mapping provides a scaffold for translation of ICD-8 to ICD-10, which enable longitudinal disease studies back to and 1969 in Denmark and to 1965 internationally with further adaption.

AB - Periodic revisions of the international classification of diseases (ICD) ensure that the classification reflects new practices and knowledge; however, this complicates retrospective research as diagnoses are coded in different versions. For longitudinal disease trajectory studies, a crosswalk is an essential tool and a comprehensive mapping between ICD-8 and ICD-10 has until now been lacking. In this study, we map all ICD-8 morbidity codes to ICD-10 in the expanded Danish ICD version. We mapped ICD-8 codes to ICD-10, using a many-to-one system inspired by general equivalence mappings such that each ICD-8 code maps to a single ICD-10 code. Each ICD-8 code was manually and unidirectionally mapped to a single ICD-10 code based on medical setting and context. Each match was assigned a score (1 of 4 levels) reflecting the quality of the match and, if applicable, a “flag” signalling choices made in the mapping. We provide the first complete mapping of the 8596 ICD-8 morbidity codes to ICD-10 codes. All Danish ICD-8 codes representing diseases were mapped and 5106 (59.4%) achieved the highest consistency score. Only 334 (3.9%) of the ICD-8 codes received the lowest mapping consistency score. The mapping provides a scaffold for translation of ICD-8 to ICD-10, which enable longitudinal disease studies back to and 1969 in Denmark and to 1965 internationally with further adaption.

KW - Conversion table

KW - Crosswalk

KW - Data harmonization

KW - Denmark

KW - Diagnosis

KW - Disease codes

KW - ICD-10

KW - ICD-8

KW - International classification of diseases

KW - Mapping

U2 - 10.1007/s10654-023-01027-y

DO - 10.1007/s10654-023-01027-y

M3 - Journal article

C2 - 37555907

AN - SCOPUS:85167357915

VL - 38

SP - 1043

EP - 1052

JO - European Journal of Epidemiology

JF - European Journal of Epidemiology

SN - 0393-2990

ER -