Relapse after long-term follow up of multibacillary patients treated by WHO multidrug regimen

Thirty-five multibacillary (MB) leprosy patients were treated with 2 years of multidrug therapy (MDT) and followed up regularly for relapse. Relapse was defined as: a) an increase of the bacterial index (BI) by 2+ over the previous value from any single site of old lesions and b) the occurrence of definite new skin lesion(s) which demonstrated a higher BI than any pre- existing lesion. After a mean duration of 72.7 ± 17.3 months of follow up per patient, seven relapses were diagnosed; the mean incubation period of relapse was 62.7 ± 18.7 months. The overall relapse rate was 20.0% (or 3.3 per 100 patient-years), very significantly higher than the figures obtained from the same group of patients analyzed 2 1/2 years earlier, indicating that relapses occurred late (at least 5 ± 2 years) after stopping MDT. Further analysis indicated that the relapse rate was closely correlated with the bacterial load of the patient, occurring far more frequently among patients with a BI of ≥4.0 before MDT or with a BI of ≥3.0 at the end of MDT. To avoid the alarmingly high relapse rate, it is proposed that the duration of MDT be doubled to 4 years in patients with an average BI of ≥4.0 before MDT.