CROSS-SECTIONAL ASSESSMENT OF ELISA REACTIVITY IN LEPROSY PATIENTS, CONTACTS, AND NORMAL POPULATION USING THE SEMISYNTHETIC ANTIGEN NATURALDISACCHARIDE OCTYL BOVINE SERUM-ALBUMIN (ND-O-BSA) IN CEBU, THE PHILIPPINES

An indirect enzyme-linked immunosorbent assay (ELISA) using natural di saccharide octyl bovine serum albumin (ND-O-BSA) as antigen was used i n testing leprosy patients, contacts and a normal population in Cebu, The Philippines, from 1985 to 1989. A total of 1413 persons were studi ed. The results suggested that ELISA reactivity and the bacterial inde x (BI) correlate in a general way. In multibacillary (MB) leprosy, pos itivity ranges from 54.2% to 92.3% among patients with a BI of < 2+ to > 4+ on the Ridley scale, with an overall average of 84.5%. Paucibaci llary (PB) leprosy patients have a low degree of reactivity, with only 15.0% ELISA positive. The test is more efficient in detecting MB than PB leprosy. The contacts of MB leprosy showed 6.5% positivity; contac ts of PB leprosy, 7.0% positivity. The normal population showed 1.7% p ositive ELISA or 17 per thousand population, which is very much less t han that of the household contacts. However, because the normal popula tion is a much larger population than the household contact population in a community, more new leprosy cases would emanate from it. Leprosy workers are concerned about the transmission of the disease to househ old contacts. However, for the reason stated above, we should be more concerned with the silent spread of the disease to the normal populati on in the community. Further studies are required along this line: One to determine whether there is a correlation between prevalence rates the rates of ELISA positivity in the normal population, the other is t o find out if the rate of ELISA positivity in the normal population of a community can be used to monitor the efficiency of a leprosy contro l program.