Diagnosis Coding Systems

There are two main coding systems that are available for associating diagnoses with a patient: ICD9 and ICD10 codes. The International Classification of Diseases (ICD) is designed to map health conditions to corresponding generic categories together with specific variations.

ICD codes are maintained by the World Health Organization, which periodically provides revisions and updates. ICD-9 was used until October 1, 2015, at which time all health systems switched to ICD-10. If the date range in your query crosses over October 1, 2015 and includes diagnoses, make sure to use both ICD-9 and ICD-10 codes for the condition of interest.