Internal Medicine Coding Alert

Question: A patient with only Medicaid coverage came to our office for a flu test. We billed 87804, which includes two tests (A and B). The carrier only paid for one test, even though we billed for two. We resubmitted with modifier 91 and got paid for both tests, but I'm not sure that was the correct way to file. What's your advice?

Texas Subscriber

Answer: You're on the right track by submitting 87804 (Infectious agent antigen detection by immunoassay with direct optical observation; influenza). Coding guidelines instruct you to report two units of 87804 if the test differentiates between influenza A and B, so you're also correct with that step.

The problem lies with the modifier you reported. Although you're submitting a claim with laboratory codes, modifier 91 (Repeat clinical diagnostic laboratory test) isn't appropriate because you didn't repeat the procedure -- you're reporting two tests within the same procedure. Submit the first unit as 87804 and the second unit as 87804 with modifier 59 (Distinct procedural service) appended.