Additional-code relationship
What we found
T63.4 first, T78.2 as an additional code
T63.4 carries a Use Additional Code instruction covering T78.2: “code, if applicable, for anaphylactic shock (T78.2)”
What to review
Report T78.2 after T63.4 when the documentation supports it.
Why it matters
A "Use additional code" note means a secondary code should follow this one to fully describe the condition when the documentation supports it.
Source / rule
CMS ICD-10-CM tabular instructional notes