The diagnosis code identifying the beneficiary's principal diagnosis.
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)