Pathology/Lab Coding Alert

Question: The lab performs a wet mount and KOH test for a vaginal smear from a patient with vaginitis. The wet mount is positive, showing clue cells, and the KOH test is negative, indicating the absence of a fungal infection. We’re having trouble with the diagnosis coding, because N76 (Other inflammation of vagina and vulva) instructs us, “Use additional code (B95-B97), to identify infectious agent.” We don’t know the infectious agent. What should we do?

Louisiana Subscriber

Answer: This is a common problem, because labs often perform just a wet mount/KOH test combination for suspected vaginitis, because the treatment doesn’t rely on specifically identifying the causative organism, if it is bacterial.

Your best bet is to report B96.89 (Other specified bacterial agents as the cause of diseases classified elsewhere) in as the second-listed code following N76.

Because you’ve ruled out a fungal infection, you would not use a code such as A59.01 (Trichomonal vulvovaginitis) or B37.3 (Candidiasis of vulva and vagina). And although the most common bacterial cause of vaginitis is Gardnerella vaginalis, you can’t code that if the lab doesn’t identify the organism.

If both the KOH and wet mount tests were negative, you should report the apparent symptoms of vaginal discharge as N89.8 (Other specified noninflammatory disorders of vagina) instead of reporting vaginitis.

Procedure tip. If the lab performs both the wet mount and KOH prep, you can code two units of 87210 (Smear, primary source with interpretation; wet mount for infectious agents [e.g., saline, India ink, KOH preps]).

If Medicare or Medicaid is the payer, you should instead code Q0111 (Wet mounts, including preparations of vaginal, cervical or skin specimens) and Q0112 (All potassium hydroxide [KOH] preparations) for the lab work.