Detection of anti-M. leprae antibodies in children in leprosy-endemic areas: A systematic review

BACKGROUND

Leprosy elimination primarily targets transmission of Mycobacterium leprae which is not restricted to patients' households. As interruption of transmission is imminent in many countries, a test to detect infected asymptomatic individuals who can perpetuate transmission is required. Antibodies directed against M. leprae antigens are indicative of M. leprae infection but cannot discriminate between active and past infection. Seroprevalence in young children, however, reflects recent M. leprae infection and may thus be used to monitor transmission in an area. Therefore, this literature review aimed to evaluate what has been reported on serological tests measuring anti-M. leprae antibodies in children without leprosy below the age of 15 in leprosy-endemic areas.

METHODS AND FINDINGS

A literature search was performed in the databases Pubmed, Infolep, Web of Science and The Virtual Health Library. From the 724 articles identified through the search criteria, 28 full-text articles fulfilled all inclusion criteria. Two additional papers were identified through snowballing, resulting in a total of 30 articles reporting data from ten countries. All serological tests measured antibodies against phenolic glycolipid-I or synthetic derivatives thereof, either quantitatively (ELISA or UCP-LFA) or qualitatively (ML-flow or NDO-LID rapid test). The median seroprevalence in children in endemic areas was 14.9% and was stable over time if disease incidence remained unchanged. Importantly, seroprevalence decreased with age, indicating that children are a suitable group for sensitive assessment of recent M. leprae infection. However, direct comparison between areas, solely based on the data reported in these studies, was impeded by the use of different tests and variable cut-off levels.

CONCLUSIONS

Quantitative anti-PGL-I serology in young children holds promise as a screening test to assess M. leprae infection and may be applied as a proxy for transmission and thereby as a means to monitor the effect of (prophylactic) interventions on the route to leprosy elimination.

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

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.

[The current challenge of imported leprosy in Spain: a study of 7 cases]

BACKGROUND

although the foci of leprosy once present in Spain are now under control and almost inactive, isolated cases are still occasionally diagnosed. Meanwhile, population migration has brought about an increase in the incidence of cases corresponding to individuals from countries where leprosy is endemic, leading to changes in the epidemiology of this disease.

OBJECTIVES

the aim of this paper was to describe the clinical, epidemiologic, dermatologic, microbiologic, and therapeutic characteristics of cases of leprosy in our department in the last 5 years.

MATERIAL AND METHODS

we report the cases of imported leprosy seen in our department between 2004 and 2009.

RESULTS

seven patients with leprosy (3 men and 4 women; age range, 26-80 years) were diagnosed; 2 were cases of tuberculoid leprosy, 2 borderline tuberculoid leprosy, and 3 indeterminate. All patients acquired the disease in South American or South African countries, but were residing in Spain at the time of diagnosis. One patient was a Spaniard, from Malaga, who had worked as a missionary in Venezuela for 25 years. The presence of the bacterium by either Ziehl-Neelsen stain or bacilloscopy could not be demonstrated in any of the patients.

CONCLUSIONS

we would like to draw attention to the changes we have observed in the characteristics of cases of leprosy seen in our department, the majority of which are imported. It is important to maintain a clinical suspicion of leprosy in cases of granulomatous dermatitis, particularly in patients from countries where the disease is endemic.

The influence of ML Flow test in leprosy classification

This is a descriptive, exploratory study correlating ML Flow, bacilloscopy and classification of paucibacillary (PB) and multibacillary (MB), involving 1,041 new leprosy cases in 13 municipalities of Minas Gerais State, from October 2002 to March 2004. Agreement between ML Flow and the classification of the number of skin lesions and bacilloscopy was moderate (K:0.51 and K:0.48, respectively); and substantial for final classification (K:0.77). From January 2000 to March 2004, the proportion of new MB cases in Minas Gerais decreased from 78.1 to 65.8%. The reduction in the percentage of MB cases was higher in health centers that participated in the ML Flow study (73.1% to 53.3%). The difference between PB and MB in the participating and non-participating health centers from January to March 2004 was statistically significant. Implementation of the ML Flow test influenced the classification of patients, suggesting a direct and beneficial impact on patient treatment and the control of the leprosy endemic in Minas Gerais, Brazil.

Nerve damage in leprosy and its management

Leprosy is the most common treatable peripheral nerve disorder worldwide. Deformity and disability result from nerve-function impairment; however, early treatment is associated with good outcome. Leprosy is often diagnosed late as many physicians have little experience with the clinical picture. Recent research using nerve conduction and thermal threshold tests has identified that nerve impairment is detectable long before it turns clinical. This discovery could have important implications for treatment because steroid therapy for nerve-function impairment that is detected clinically is unsatisfactory. Evidence that clinical neuropathy represents only the 'tip of the iceberg' of nerve damage, together with an understanding that the underlying inflammatory immunological processes require longer, more-aggressive treatment, could help usher in new and more-successful approaches to the treatment of nerve-function impairment in leprosy. This Review focuses on the neurological manifestations of leprosy and the pathophysiology of nerve damage. Early detection and treatment of nerve-function impairment are crucial for outcome, so special emphasis is given to developments in detecting and treating nerve impairment in leprosy early.

Association of the ML Flow serologic test to slit skin smear

A descriptive, exploratory study was conducted analyzing the association of covariables in the results of the ML Flow serological test and slit skin smear. A total of 60 leprosy cases diagnosed at the state Sanitary Dermatology Referral Center were investigated. Slit skin smear samples were collected from four sites and the results were expressed by the bacillary index. ML Flow was registered in both qualitative and semi-quantitative terms. Cohen's kappa coefficient was used to study the agreement with Landis and Koch's observer criteria for interpretation. For statistical analysis, the logistic regression model and Kruskal-Wallis test were used. ML Flow showed a strong association with slit skin smear results, since a gradual increase in BI was accompanied by a semi-quantitative rise in antibody levels measured by ML Flow, with 100% positivity in cases presenting a positive slit skin smear. Given its strong correlation to slit skin smear, the results of this study provide evidence that the ML Flow test could be a valuable auxiliary tool in the classification and treatment of leprosy patients.