Relapse rates in lepromatous leprosy according to treatment regularity.

In Gudiyatham Taluk, South India, 1008 lepromatous (LL) and borderline lepromatous (BL) patients were studied. They had previously been smear positive, had attained smear negativity, and continued on DDS monotherapy. "Relapse" was defined as the reappearance of Mycobacterium leprae in skin smears. The area is endemic for leprosy. The lower relapse rates in the first three years of smear negativity alone were associated with more-regular treatment during both past smear positivity and smear negativity. From the fourth year of smear negativity onward, only the more-regular treatment during smear negativity was associated with lower relapse rates; whereas patients with more-regular treatment during past smear positivity had no lower risk of relapse than those with less-regular treatment. The finding that regularity of treatment during smear positivity seems to have no effect on relapse rates beyond the third year of smear negativity is discussed. In a leprosy-endemic area, it is argued that beyond the first three years of smear negativity in an LL or BL patient, sources of M. leprae outside the patient may be more responsible for relapse than the patient's own bacilli.