MCMCB Pro
T78.41XA

T78.41XAArthus phenomenon, initial encounter

Billable / specific codeICD-10-CM

T78.41XA is a billable, specific ICD-10-CM code for arthus phenomenon, initial encounter. It is valid for submission on a claim.

7th character "A" — initial encounter

The appropriate 7th character is to be added to each code from category T78

A
initial encounter
D
subsequent encounter
S
sequela

Inclusion terms

Alternative wordings a physician may use in the chart for this same code.

  • Arthus reaction

Risk adjustment

T78.41XA does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Medicare coverage

T78.41XA is named in 3 Medicare coverage policies 3 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.

  • A57181Billing and Coding: Allergy Testing
  • A57181Billing and Coding: Allergy Testing
  • A57361Billing and Coding: Monitored Anesthesia Care

Related codes at this level

Codes that share T78.41. If T78.41XA is not quite right, the correct code is usually one of these.

Questions about T78.41XA

Is T78.41XA a billable ICD-10-CM code?
Yes. T78.41XA is a billable, specific ICD-10-CM code and is valid for submission on a claim.
Where does T78.41XA sit in the tabular list?
Injury, poisoning and certain other consequences of external causes (S00-T88), in the block Other and unspecified effects of external causes (T66-T78).
ICD-10-CMFY2026-Apr· effective April 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release — see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.