Despite the widespread use of multidrug
therapy for
treatment, delays in clinical recognition and under-reporting of
leprosy indicate that Mycobacterium leprae transmission is continuing. Thus,
leprosy is likely to persist as a significant burden on health systems in many regions. In this study, we combined 2 previously characterized
leprosy antigens,
leprosy IDRI diagnostic-1 (LID-1) and ND-O, into the single fusion complex (ND-O-LID) and determined the serum antibody responses of
leprosy patients from Colombia and the Philippines. Following confirmation that
antibodies recognized each component within the conjugate, we assessed the performance of a rapid
enzyme-linked
immunosorbent assay (ELISA) system (
Leprosy Detect(TM) fast ELISA; InBios International, Inc., Seattle, WA, USA) based on ND-O-LID capable of generating results within 1.5hours of sample addition. We found ELISA results correlated with the bacteriological index and Ridley-Jopling categorization, with
lepromatous leprosy patients having the highest responses, while those of
borderline tuberculoid patients were lower. Multibacillary (MB)
leprosy patients were distinguished with a high degree of sensitivity (95.7%) and specificity (93.2%), suggesting that this ELISA could potentially replace invasive and insensitive skin slit smear procedures that require expert microscopic examinations. Due to the speed and robustness of this assay, we believe this is an excellent tool for detecting MB
leprosy patients in a simple and highly-quantitative manner.