In a previous study an index (sigma 3) resulting from the summation of three parameters, i.e., presence of bacilli, even in small numbers, in various dermal structures, multiple positive
antigen sites as detected by anti-BCG antiserum and dermal nerve involvement, identified 72.22% of cases of indeterminate
leprosy which progressed to
multibacillary leprosy. The present study was undertaken to investigate possible parameters which might be indicative of indeterminate
leprosy which would persist unchanged or be cured (treated cured patients). Thirty treated cured indeterminate
leprosy patients were selected from the files of the São Paulo Health Institute and studied by histopathological, immunohistochemical and statistical methods similar to those employed in the previous study. The sigma 3 index was 4.10 +/- 0.60, a finding that places this group of patients in a position close to that of patients changing to
paucibacillary leprosy but statistically different from that of patients progressing to
multibacillary leprosy. Moreover, it was found that patients belonging to this group have heterogeneous single parameters, some of them suggestive of multibacillary and others of
paucibacillary leprosy. Immunologically based techniques mainly employing rabbit anti-BCG serum as the primary antibody have proved to be valuable to detect
antigen sites in biopsies from indeterminate
leprosy patients and should be used together with the bacillary index during the follow up and clinical discharge control of such patients. In the present study, we show that clinical discharge of these patients did not mean a complete clearance of bacillary
antigens.