The diagnosis code in the 4th position identifying the condition(s) for which the beneficiary is receiving care.
On October 1, 2015 the conversion from the 9th version of the International Classification of Diseases (ICD-9-CM) to version 10 (ICD-10-CM) occurred. ICD-10 has more than 70,000 unique diagnosis codes compared to approximately 14,000 ICD-9 codes, which allows for more detail surrounding diagnoses.
For ICD-9 diagnosis codes, this is a 3-5 digit numeric or alpha/numeric value; it can include leading zeros.
The lower the number in the variable name, the more important the diagnosis in the patient treatment/billing (i.e., ICD_DGNS_CD1 is considered the primary diagnosis).
Source: Medicare Advantage Organizations (MAOs)