Unexpectedly high leprosy seroprevalence detected using a random surveillance strategy in midwestern Brazil: A comparison of ELISA and a rapid diagnostic test

Abstract

BackgroundLeprosy diagnosis is mainly based on clinical evaluation, although this approach is difficult, especially for untrained physicians. We conducted a temporary campaign to detect previously unknown leprosy cases in midwestern Brazil and to compare the performance of different serological tests.MethodsA mobile clinic was stationed at the main bus terminal in Brasília, Brazil. Volunteers were quizzed and given a clinical exam to allow categorization as either patients, known contacts of patients or non-contacts, and blood was collected to determine anti-PGL-I and anti-LID-1 antibody titers by ELISA and by the NDO-LID rapid test. New cases of leprosy and the impact of performing this broad random surveillance strategy were evaluated. Accuracy values and concordance between the test results were evaluated among all groups.ResultsFour hundred thirty-four individuals were evaluated, and 44 (10.1%) were diagnosed with leprosy. Borderline forms were the most frequent presentation. Both tests presented higher positivity in those individuals with multibacillary disease. Serological tests demonstrated specificities arround 70% for anti-PGL-1 and anti-LID ELISA; and arround 40% for NDO-LID. Sensitivities ranged from 48 to 62%. A substantial agreement between NDO-LID and ELISA with concomitant positive results was found within leprosy patients (Kappa index = 0.79 CI95% 0.36–1.22).ConclusionsThe unexpectedly high leprosy prevalence in this population indicates ongoing community-based exposure to Mycobacterium leprae antigens and high rates of subclinical infection. All tests showed low specificity and sensitivity values and therefore cannot be considered for use as stand-alone diagnostics. Rather, considering their positivity among MB patients and non-patients, these tests can be considered effective tools for screening and identifying individuals at high risk who might benefit from regular monitoring.

Field-friendly serological tests for determination of M. leprae-specific antibodies

“…The use of a reader (Smart Reader) to analyse immunogold LF strips similar to the Gold-LFA test for detection of M. leprae -specific antibodies has been described 23 , 24 and demonstrated that results by visual interpretation and results read by Smart Reader agreed moderately (κ index: 0,55) 25 . However, haemolysis of red blood cells when using the immunogold label may hamper accurate measurements and visualisation of low positives, contrary to the UCP-LFA format which is a virtually background-free reporter technology 21 .…”

Transmissão da hanseníase na Bahia, 2001-2015: modelagem a partir de regressão por pontos de inflexão e estatística de varredura espacial*

“…We refer to this process as 'pseudo decline' and suggest that it may be the result of high hidden prevalence of the disease, allowing one to defend that the true number of cases is even higher than those currently recorded on official information systems. 5,[10][11] The first set of evidence relates to the maintenance of the transmission chain in the state, shown by the analysis of the detection coefficients in the general population and in those under 15 years old. The stationary behavior of overall detection, different to the pattern found in other places in Brazil, [12][13] and the fact of this indicator being practically the same at the beginning and the end of the series, contribute to supporting the thesis of active leprosy transmission in the state of Bahia.…”

Biotechnological and Immunological Platforms Based on PGL-I Carbohydrate-Like Peptide of Mycobacterium leprae for Antibodies Detection Among Leprosy Clinical Forms

“…The application of the surface antigen of M. leprae, PGL-I, as serological marker has been well-established (Moura et al, 2008), especially because of its high correlation with high BI and with MB forms of leprosy (Cho et al, 1983), with important role in the operational classification of patients directly affecting the choice of multidrug therapy regimens . Furthermore, its use in contacts' monitoring demonstrated that individuals with high anti-PGL-I titers present a higher risk to develop leprosy and may indicate subclinical infection (Bazan-Furini et al, 2011;Frade et al, 2017).…”

“…The phenolic glycolipid I (PGL-I) is one of the main antigens on the cell wall of Mycobacterium leprae and has important roles in the pathogenesis and diagnosis of leprosy . The presence of anti-PGL-I antibodies has been mainly correlated with multibacillary forms of the leprosy clinical spectrum and with higher bacilloscopic index (BI) (Lobato et al, 2011), with important applications in household contacts' monitoring (Frade et al, 2017) and to establish the therapeutic regimens with multidrug therapy .…”