Pathology/Lab Coding Alert

Question: We've gotten denials when we bill 87324 x 2 for two EIA tests for C. diff toxin A and toxin B. Can our lab code for tests for both toxins if we use the same lab method for both tests?

Virginia Subscriber

Answer: Yes, you can bill for both Clostridium difficile toxin A and toxin B if a physician orders the tests for medically necessary reasons. C. difficile is a bacterium that can cause diarrhea and can worsen to severe colon inflammation. Although C. difficile occurs in most normal, healthy digestive tracts, the organism can create problems when allowed to grow unchecked, as might happen when a patient takes antibiotics to treat another illness.

C. difficile produces toxins A and B that can cause the diarrhea and colitis. That's why lab tests focus on identifying the presence of one or both of these toxins.

Labs can detect the toxins by different methods, such as those described by the following codes:

• 87230 -- Toxin or antitoxin assay, tissue culture (e.g., Clostridium difficile toxin)

• 87324 -- Infectious agent antigen detection by enzyme immunoassay technique, qualitative or semiquantitative, multiple step method; Clostridium difficile toxin(s).

Some labs perform 87230 for toxin A and 87324 for toxin B. If that's what your lab does, you should report both codes.

More commonly, labs perform two separate enzyme immunoassay (EIA) tests, one for each toxin. Because the EIA test allows for more rapid results, performing two units of the test, one for toxin A and one for toxin B, is not unusual. But that's when some labs run into payment problems.

Do this: According to a CPT text note preceding infectious agent codes, you should "use modifier 59 (Distinct procedural service) when separate results are reported for different species or strains that are described by the same code."

Beware: Certain payers require you to use modifier 91 (Repeat clinical diagnostic laboratory test) instead of modifier 59, so follow your payer's instructions. Successfully using a modifier for difficile toxin A and toxin B will earn an extra $17.52 that your lab deserves, based on the Clinical Laboratory Fee Schedule national limit amount for 87324.

-- Reader Questions and You Be the Coder were prepared with the assistance of R.M. Stainton Jr., MD, president of Doctors' Anatomic Pathology Services in Jonesboro, Ark.