Pathology/Lab Coding Alert

Question: Our lab received an order for IgG and IgM antibody testing for toxoplasmosis for a pregnant patient. How should we report the procedure and diagnosis codes?

New Hampshire Subscriber

Answer: The infectious agent that causes toxoplasmosis is Toxoplasma gondii. You should report a serology test for the two immunoglobulin classes IgG and IgM for Toxoplasma using the following codes:

• 86777 (Antibody; Toxoplasma)
• 86778 (… Toxoplasma, IgM)

Clinicians can use the results of the IgG antibody test to determine if the person has been infected with the organism. The IgM antibody may provide further information to estimate when the person was infected. The IgM results are particularly important for pregnant women because the organism can transfer across the placenta and cause serious pathology in the newborn.

Two classes: Coders may be confused because 86777 doesn’t indicate that it is for IgG. But CPT^® provides instructions that clarify the situation: “When a coding option exists for reporting IgM specific antibodies … the corresponding nonspecific code … may be reported for performance of either an antibody analysis not specific for a particular immunoglobulin class or for an IgG analysis.”

Diagnosis: Toxoplasma gondii is a protozoan parasite. That means the appropriate diagnosis code for the testing is Z11.6 (Encounter for screening for other protozoal diseases and helminthiases).

Because parasites encompass many types of organisms, Z11.6 is a more specific code than the similar code Z11.8 (Encounter for screening for other infectious and parasitic diseases).

If the test(s) are positive for toxoplasmosis, the ordering clinician may use O35.8 (Maternal care for other (suspected) fetal abnormality and damage) for any subsequent procedures or tests.