ED Coding and Reimbursement Alert

Question: A patient came in to the ED with an allergic reaction, but we weren't able to pinpoint the specific allergen. Should we report T78.40- (Allergy, unspecified...)?

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Answer: Not necessarily. The "T" codes fall under the category of "Injury, poisoning and certain other consequences of external causes" within the ICD-10-CM. Unless the patient is having an acute but confirmed allergic response, you should not consider a T code diagnosis. If a patient presents with allergies of an unspecified nature without an acute allergic reaction taking place, you should only code the signs and symptoms until an allergy test has been performed.

In the case that a patient does present with an initial, unspecified allergic reaction, such as wheezing, you will opt for code T78.40XA (Allergy, unspecified, initial encounter), indicating that this is the first encounter for the patient's presenting symptoms. Your other seventh digit options are D (Subsequent encounter) and S (Sequela). If the patient is returning for a follow-up after receiving, for example, a nebulizer treatment, the use of the seventh digit D would be appropriate.

Taking a brief look at "allergy" under the ICD-10 index, you'll see the plethora of options you have to choose from. While the unspecified T codes (for allergic reactions) do cross-reference with allergy testing CPT® codes in the coding crosswalk, the same cannot necessarily be said for evaluation and management (E/M) visits. In order to ensure payment for these encounters, you will want to make sure your provider offers any and all information available surrounding the patient's allergy diagnosis.

The reason for this extends beyond simple reimbursement purposes. The correct allergy ICD-10 code is ultimately dependent on the patient's comorbidities and/or associated diagnoses.