International Classification of Diseases, Period!

The International Statistical Classification of Diseases and Related Health Problems (ICD) is the most standardized set of codes used in healthcare and covers both diagnoses (CM) and procedures (PCS).

Every medical claim is required to have at least one ICD-CM diagnosis code to explain why the service was rendered. All acute inpatient claims are required to use ICD procedure codes to identify the service or service performed. On October 1, 2015, the United States healthcare system switched from using the 9th revision of ICD to the 10th revision.

Both versions of ICD-CM (9 & 10) diagnostic codes use a 6-character format: XXX.XX. ICD-PCS version 9 uses a 5-character format: XX.XX; version 10 CM uses XXX.XXX and PCS uses XXXXXXX. Some claim extracts will include the ‘.’ and some will drop it.

Occasionally claims extracts will merge from multiple sources and include observations with and without the ‘.’ as shown in the associated DPS data. For this reason, it is good practice to drop the ‘.’ from both your processed medical claims file and from any code maps (e.g. dx labels) and crosswalks (e.g CCS).

Be careful to retain leading zeros when dropping the ‘.’. We’ll talk more about why in a future post.

Dr. Olmsted has a Ph.D. in Economics and has been working with healthcare data for over twenty years for companies including IHCIS (now part of Optum), RTI International, and Health Dialog.