Follow-up of lepromatous (LL and BL) patients on dapsone (DDS) monotherapy after attainment of smear negativity in Gudiyatham Taluk, South India.

At the Schieffelin Leprosy Research and Training Centre, Karigiri, India, an analysis of "relapse" rates was undertaken on all the 1293 residents of Guidyatham Taluk who were known to have lepromatous (LL) or borderline lepromatous (BL) leprosy and had attained "smear negative" status. "Relapse" was defined as the reappearance of acid-fast bacilli (AFB) in skin smears, whether by reinfection from other patients or from the patient's own persisting organisms. The "relapse" rate decreased steadily with the time elapsed after the attainment of smear negativity: 2.8% (2.8 per 100 patients per year) in the initial two years; 1.1% from the third year onwards; and 0.9% from the ninth year onwards. Of the 1293 patients, 694 (53.7%) had taken greater than or equal to 80% regular dapsone (DDS) treatment during smear negativity. In this group, the "relapse" rate from the third year onwards was only 0.7% per year. The vast majority (90.9%) of LL and BL patients on DDS monotherapy in the area had at some point attained smear negative status. It appears important to study whether a limited period of DDS monotherapy after the attainment of negative skin smears would be an effective alternative to life-long DDS treatment in LL and BL patients.