An initial negative test for suspected Buruli ulcer should be treated with caution and repeated, Victorian infectious diseases specialists say.

While PCR testing of lesion material is the most accurate way of diagnosing the disease, the result for a swab sample may be negative if the lesion is not yet ulcerated, write the authors of a research letter published in the Medical Journal of Australia.

“A negative PCR test result for a suspicious lesion does not exclude Mycobacterium ulcerans disease; the test should be repeated, preferably with a punch biopsy specimen,” says the group, led by Associate Professor Daniel O’Brien from University Hospital Geelong.

“PCR testing of non-ulcerative lesions requires biopsy (for fresh tissue) or fine needle aspiration (for tissue fluid).”