FIELD-EVALUATION OF AN ELISA TO DETECT ANTIBODY IN LEPROSY PATIENTS AND THEIR CONTACTS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 52  (1) , 26-33
Abstract
A method for detecting antibody by ELISA, using autoclaved Mycobacterium smegmatis as the antigen, was developed. Evaluation was performed on eluates from 25 .mu.l aliquots of finger-prick blood dried on filter paper discs in 2 high-incidence populations in Ponape, Micronesia. Results were obtained from 228 nonleprosy cases bled in 1980 and rebled and re-examined in 1982. For those who had been ELISA positive 2 yr earlier, the leprosy attack rate during the intervening 2 yr was at least twice as high as among those who had been negative; shortening the screening interval to 1 yr plus doing confirmatory retests on new seroconverters was estimated to increase the relative risk (or predictive power) to > 6-fold, including all impending multibacillary cases. Elevated antibody levels were detected up to 2 yr prior to clinical onset of disease in 70% of new cases. Asymptomatic conversion (rising titer) and reversion (falling titer) were observed. Among 150 biopsy-proven cases, ELISA results suggest that fall of titer in most uncomplicated paucibacillary cases was rapid (months), but in multibacillary cases was more gradual (years), probably paralleling responses to treatment with titers rising in reactivation. Evidently, this technique, with an improved antigen, may be useful in leprosy control programs, for detecting candidates for preventive treatment and for following responses to therapy.