How it works
ICD-10-CM codes have three to seven characters, with later characters adding detail such as laterality, severity or encounter type. The code set is updated every year with changes effective October 1, and occasionally in April. Diagnosis codes on a claim are linked to each service line through diagnosis pointers.
Why it matters
Diagnosis codes support medical necessity. Codes that are not specific enough, are invalid for the date of service or do not match a payer’s coverage policy lead to denials. They also feed risk adjustment in Medicare Advantage and other value-based programs.
Example
A claim lists an unspecified diagnosis when the note documents the specific type and side. Coding the documented detail makes the claim complete and accurate.