Adaptation and validation of a coding algorithm for the Charlson Comorbidity Index in administrative claims data using the SNOMED CT standardized vocabulary

Table 4 Code mapping diagnostics of discrepant ICD-9/10-CM codes between coding algorithms

Comorbid condition	Multiple ICD codes to one SNOMED CT code		Deprecated ICD code unmapped to SNOMED CT code	Specificity of SNOMED CT to ICD code mapping
Comorbid condition	Information gain^a	Added noise^b	Deprecated ICD code unmapped to SNOMED CT code	Specificity of SNOMED CT to ICD code mapping
Myocardial infraction	2	0	0	0
Congestive heart failure	0	3	0	1
Peripheral vascular disease	15	9	0	0
Cerebrovascular disease	22	0	0	0
Dementia	4	0	0	0
Chronic pulmonary disease	3	2	0	0
Rheumatic disease	9	121	0	0
Peptic ulcer disease	0	0	0	0
Mild liver disease	20	1	0	1
Diabetes without chronic complications	5	23	3	0
Diabetes with chronic complications	30	181	0	0
Hemiplegia or paraplegia	6	12	0	0
Renal disease	18	12	0	0
Malignancy, except skin neoplasms	2	36	120	10
Moderate or severe liver disease	2	3	0	0
Metastatic solid tumor	0	19	0	0
AIDS/HIV	0	0	0	0
Total	138	422	123	12

^aInformation gain: Discrepant code mapping to clinically relevant code
^bAdd noise: Discrepant code mapping to clinically irrelevant code
ICD-9/10-CM International Classification of Diseases, Ninth and Tenth Revision, Clinical Modification

ISSN: 1472-6947