Coding for food allergy testing

The Advocacy Council regularly receives queries from members on how to correctly code specific scenarios. Recently we received a request for assistance from a practice regarding denied claims for food testing.


Member question: We are billing for food testing using T781XX_ (A or S), and/or T78 _X_ (01, 02, 05, 08 for example) (A or S). These are being denied as having missing/incomplete/invalid principal diagnosis. We have been unable to contact anyone at the carrier who can help us. Have you had any reports of this? What do you suggest we do?

The Advocacy Council coding experts explain: The Advocacy Council has not seen this as a widespread issue. While the T78 series of ICD-10 codes requires a 7th character, it is usually A or D. It is very unusual that an allergist would use S (sequela) as the 7th character. Also, it’s usually the insurance carrier that dictates which to use – usually D, but it could be A.

Seventh Characters

  • A – Initial encounter is used for each encounter where the patient is receiving active treatment for the condition.
  • D – Subsequent encounter is used for encounters after the patient has completed active treatment of the condition and is receiving routine care for the condition during the healing or recovery phase.
  • S – Sequela – complications or conditions that arise as a direct result of a condition.

Insurance carriers often want the symptom first, such as urticaria, as a primary diagnosis code, and then the CPT for the allergy to the food. 

If you don’t know the specific food, if the specific food is not assigned a diagnosis code, or if the reaction was not anaphylaxis, you can use the T78.1XXD ICD-10 code. For example, L50.0 (urticaria – allergic); T78.1XXD (other adverse food reactions, not elsewhere classified).

If you have experienced claim rejections for this reason, try billing again with an explanation and using the additional symptom diagnosis code that would fit with food allergy.

Presenting correctly coded claims to the carrier ensures your “clean claim” will fly through the review process, ending denials. You’ll save staff time dedicated to appeals, and there won’t be delays in your cash flow, since claims will be paid the first time submitted.

Do you have a coding conundrum of your own? Share it with us!
And check out our coding toolkit for more helpful resources.

Advocacy Issue: 
Billing, Coding & Payments