Evaluation of qPCR-Based Assays for Leprosy Diagnosis Directly in Clinical Specimens

The increased reliability and efficiency of the quantitative polymerase chain reaction (qPCR) makes it a promising tool for performing large-scale screening for infectious disease among high-risk individuals. To date, no study has evaluated the specificity and sensitivity of different qPCR assays for leprosy diagnosis using a range of clinical samples that could bias molecular results such as difficult-to-diagnose cases. In this study, qPCR assays amplifying different M. leprae gene targets, sodA, 16S rRNA, RLEP and Ag 85B were compared for leprosy differential diagnosis. qPCR assays were performed on frozen skin biopsy samples from a total of 62 patients: 21 untreated multibacillary (MB), 26 untreated paucibacillary (PB) leprosy patients, as well as 10 patients suffering from other dermatological diseases and 5 healthy donors. To develop standardized protocols and to overcome the bias resulted from using chromosome count cutoffs arbitrarily defined for different assays, decision tree classifiers were used to estimate optimum cutoffs and to evaluate the assays. As a result, we found a decreasing sensitivity for Ag 85B (66.1%), 16S rRNA (62.9%), and sodA (59.7%) optimized assay classifiers, but with similar maximum specificity for leprosy diagnosis. Conversely, the RLEP assay showed to be the most sensitive (87.1%). Moreover, RLEP assay was positive for 3 samples of patients originally not diagnosed as having leprosy, but these patients developed leprosy 5–10 years after the collection of the biopsy. In addition, 4 other samples of patients clinically classified as non-leprosy presented detectable chromosome counts in their samples by the RLEP assay suggesting that those patients either had leprosy that was misdiagnosed or a subclinical state of leprosy. Overall, these results are encouraging and suggest that RLEP assay could be useful as a sensitive diagnostic test to detect M. leprae infection before major clinical manifestations

Integrative literature review of the reported uses of serological tests in leprosy management

Abstract: An integrative literature review was conducted to synthesize available publications regarding the potential use of serological tests in leprosy programs. We searched the databases Literatura Latino-Americana e do Caribe em Ciências da Saúde, Índice Bibliográfico Espanhol em Ciências da Saúde, Acervo da Biblioteca da Organização Pan-Americana da Saúde, Medical Literature Analysis and Retrieval System Online, Hanseníase, National Library of Medicine, Scopus, Ovid, Cinahl, and Web of Science for articles investigating the use of serological tests for antibodies against phenolic glycolipid-I (PGL-I), ML0405, ML2331, leprosy IDRI diagnostic-1 (LID-1), and natural disaccharide octyl-leprosy IDRI diagnostic-1 (NDO-LID). From an initial pool of 3.514 articles, 40 full-length articles fulfilled our inclusion criteria. Based on these papers, we concluded that these antibodies can be used to assist in diagnosing leprosy, detecting neuritis, monitoring therapeutic efficacy, and monitoring household contacts or at-risk populations in leprosy-endemic areas. Thus, available data suggest that serological tests could contribute substantially to leprosy management

DNA amplification for detection of leprosy and assessment of efficacy of leprosy chemotherapy

Polymerase chain reaction (PCR) for the detection of Mycobacterium leprae was applied to fresh skin biopsies and slit-skin smears from 122 untreated leprosy patients. The PCR positivity rates in biopsies were 95.6% in multibacillary (MB) cases and 44.2% in paucibacillary (PB) cases. Following 1 month of treatment, MB cases declined by 54.3% and PB cases by 61.8% of initial values. Six-month values also declined from initial positivity rates to 50.3% and 53.8% of initial values in MB and PB, respectively. Larger declines in the rate of positivity were seen for skin-smear samples at 1 and 6 months in both MB and PB, but overall PCR positivity rates were lower than biopsy rates for M. lepra

Use of NASBA RNA amplification for detection of Mycobacterium leprae in skin biopsies from untreated and treated leprosy patients

This study was performed to assess the value of NASBA RNA amplification of a 16S rRNA target for the detection of presumably viable Mycobacterium leprae in sections of skin biopsies from leprosy patients. The NASBA positivity rate was 90.4% (84/93) for untreated multibacillary (MB) patients [bacterial index (BI) > or = 2] and 16.7% (8/48) for the untreated paucibacillary (PB) patients (BI <2). NASBA positivity showed a good concordance with the presence of solidly stained M. leprae [morphological index (MI)] in skin biopsies from leprosy patients, but no relationship could be demonstrated between the strength of the NASBA signals and the BI. Furthermore, the usefulness of the detection of 16S rRNA by NASBA to monitor the efficacy of leprosy treatment was investigated using an additional 154 biopsy specimens analyzed from 80 MB patients during the course of treatment. The NASBA positivity rate declined during treatment. A significant decrease was observed after only 1-3 months. These results favor the view that detection of RNA by NASBA may reflect the viability of M. lepra