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
leprosy problem may turn out to be very useful in
leprosy control programs. An operational function of serology within the
leprosy control services requires a simple test system. We have developed a simple dipstick assay for the detection of
antibodies to PGL-I and compared its performance 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 sera; the agreement beyond chance (Kappa value) was 0.92. No significant difference was found between the dipstick assay and the ELISA when seropositivity rates obtained in groups of
leprosy patients, household contacts, and controls were compared. The interpretation of the dipstick results as positive or negative was unequivocal, as illustrated by the high agreement between different persons reading the test (Kappa values > 0.88). Storage of the only
reagents required, the dipsticks and the stabilized detection
reagent, up to three weeks under tropical conditions of high temperatures, high humidity, and exposure to light, did not influence the results of the assay. The dipstick assay described here is an easy-to-perform method for the detection of
IgM antibodies to PGL-I of M. leprae; it does not require any special equipment and 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 epidemiologic mapping of
leprosy.