Assessment of the accuracy of 11 different diagnostic tests for the detection of Schistosomiasis mansoni in individuals from a Brazilian area of low endemicity using latent class analysis

Abstract

BackgroundSchistosomiasis is a parasitic disease associated with poverty. It is estimated that 7.1 million people are infected with Schistosoma mansoni in Latin America, with 95% of them living in Brazil. Accurate diagnosis and timely treatment are important measures to control and eliminate schistosomiasis, but diagnostic improvements are needed to detect infections, especially in areas of low endemicity.MethodologyThis research aimed to evaluate the performance of 11 diagnostic tests using latent class analysis (LCA). A cross-sectional survey was undertaken in a low endemicity area of the municipality of Malacacheta, Minas Gerais, Brazil. Feces, urine, and blood samples were collected from 400 residents older than 6 years of age, who had not been treated with praziquantel in the 12 months previous to the collection of their samples. The collected samples were examined using parasitological (Helm Test® kit Kato-Katz), nucleic acid amplification tests -NAATs (PCR, qPCR and LAMP on urine; PCR-ELISA, qPCR and LAMP on stool), and immunological (POC-CCA, the commercial anti-Schistosoma mansoni IgG ELISA kit from Euroimmun, and two in-house ELISA assays using either the recombinant antigen PPE or the synthetic peptide Smp150390.1) tests.ResultsThe positivity rate of the 11 tests evaluated ranged from 5% (qPCR on urine) to 40.8% (commercial ELISA kit). The estimated prevalence of schistosomiasis was 12% (95% CI: 9–15%) according to the LCA. Among all tests assessed, the commercial ELISA kit had the highest estimated sensitivity (100%), while the Kato-Katz had the highest estimated specificity (99%). Based on the accuracy measures observed, we proposed three 2-step diagnostic approaches for the active search of infected people in endemic settings. The approaches proposed consist of combinations of commercial ELISA kit and NAATs tests performed on stool. All the approaches had higher sensitivity and specificity than the mean values observed for the 11 tests (70.4 and 89.5%, respectively).ConclusionWe showed that it is possible to achieve high specificity and sensitivity rates with lower costs by combining serological and NAATs tests, which would assist in the decision-making process for appropriate allocation of public funding aiming to achieve the WHO target of eliminating schistosomiasis as a public health problem by 2030.

Evaluation of sensitivity and specificity of Kato-Katz and circulating cathodic antigen in terms of Schistosoma japonicum using latent class analysis

“…This is likely due to the appearance characteristic of Schistosoma eggs by microscopy. Likewise, KK showed a higher specificity than CCA in other LCA studies 10 – 12 , 14 – 18 , 28 . Moreover, recent studies have raised concerns that CCA may have low specificity.…”

“…A series of studies have evaluated the test performances of CCA and KK as well as the infection prevalence in S. mansoni using LCA 10 , 28 , despite a lack of previous research on S. japonicum . Some LCA models incorporated test results not only from KK and CCA but also from other methods such as ELISA 11 , 12 , polymerase chain reaction (PCR) 12 – 15 , circulating anodic antigen (CAA) 9 , 16 , DNA TaqMan 17 , and loop-mediated isothermal amplification (LAMP) 12 together.…”

FioSchisto’s expert perspective on implementing WHO guidelines for schistosomiasis control and transmission elimination in Brazil

“…For localities in the process of eliminating transmission, where the predictive values of serological tests are compromised given the low incidence of the disease, and since no single diagnostic test is capable of accurately detect schistosomiasis in this epidemiological scenario, FioSchisto endorses the two-step diagnostic strategy recommended by WHO. It is suggested that the first screening stage should be performed using commercial serological tests with high sensitivity and the second stage should use a molecular test, such as quantitative Polymerase Chain Reaction (qPCR) (54), which, despite being more complex, have higher sensitivity compared to Kato-Katz method and a higher level of specificity. It is worth noting that the COVID-19 pandemic has shown that Brazil has the infrastructure needed to perform molecular tests, improving diagnosis and reducing costs if implemented on a larger scale.…”

Development and assessment of a novel gold immunochromatographic assay for the diagnosis of schistosomiasis japonica

“…In addition to conventional parasitological diagnostics, there are a number of other diagnostic methods available for the detection of schistosome infections (4)(5)(6)(7)(8). Improved coprological tests, such as the saline gradient method (9), formalin-ethyl acetate sedimentationdigestion (FEA-SD) (10) and Helmintex method (i.e., isolates eggs from fecal samples with the use of paramagnetic particles in a magnetic field) (11) showed an increased diagnostic sensitivity compared with the traditional techniques; yet are usually labour-intensive and have a lengthy processing time.…”