Incidence of "chance" smear positivity among MB leprosy patients after MDT.

Multidrug therapy (MDT) was introduced in 1982. Nine hundred eighty multibacillary (MB) leprosy patients had successfully completed the MDT administered for a minimum of two years or till skin smear negativity, whichever was later, as recommended by the World Health Organisation (WHO). During surveillance, 2.24% of them revealed presence of acid-fast bacilli (AFB) in the skin smear. They did not have any clinical evidence suggestive of relapse. Subsequent followup (without antileprosy chemotherapy) for periods ranging from one to eight years was uneventful. We have called this as "chance smear positivity" where a few bacilli, yet to be cleared by the immune system, were picked up by routine skin smear examination.