A SIMPLE DIPSTICK ASSAY FOR THE DETECTION OF ANTIBODIES TO PHENOLIC GLYCOLIPID-I OF MYCOBACTERIUM-LEPRAE

Among the many reported applications of the detection of antibodies to phenolic glycolipid-I (PGL-I) of Mycobacterium leprae, in particular, the use of seroprevalence as an indicator of the magnitude of the lep rosy problem may turn out to be very useful in leprosy control program s. An operational function of serology within the leprosy control serv ices requires a simple test system. We have developed a simple dipstic k assay for the detection of antibodies to PGL-I and compared its perf ormance with that of an ELISA. A high degree of agreement (97.2%) was observed between the ELISA and the dipstick assay when tested on 435 s era; the agreement beyond chance (Kappa value) was 0.92. No significan t difference was found between the dipstick assay and the ELISA when s eropositivity rates obtained in groups of leprosy patients, household contacts, and controls were compared. The interpretation of the dipsti ck results as positive or negative was unequivocal, as illustrated by the high agreement between different persons reading the test (Kappa v alues > 0.88). Storage of the only reagents required, the dipsticks an d the stabilized detection reagent, up to three weeks under tropical c onditions of high temperatures, high humidity, and exposure to light, did not influence the results of the assay. The dipstick assay describ ed here is an easy-to-perform method for the detection of IgM antibodi es to PGL-I of M. leprae; it does not require any special equipment an d the highly stable reagents make the test robust and suitable for use in tropical countries. An internal control validates the performance of the assay. This dipstick assay may be the method of choice for epid emiologic mapping of leprosy.