Evaluation of the recombinant protein Sh-TSP-2 for the serological diagnosis of imported urogenital schistosomiasis and comparison with commercially available tests

Abstract

Different agencies have emphasized the need to evaluate current serological methods for screening patients with suspected urogenital schistosomiasis. However, there is still a lack of evidence regarding the most appropriate methods for this purpose. Here we assessed the diagnostic efficacy of a newly developed serological technique that utilizes the recombinant protein Sh-TSP-2, applied to the urine and serum of migrants suspected of having urogenital schistosomiasis. The sensitivity, specificity, positive and negative predictive values of an in-house enzyme-linked immunosorbent assay (ELISA) using the recombinant protein Sh-TSP-2 were analysed and compared with other commercial serological methods. Due to the limitations of microscopy as a perfect reference method, a latent class analysis (LCA) and composite reference standard (CRS) approach was used to determine the sensitivity and specificity of each test. According to the LCA model, the commercial tests NovaLisa^® and immunochromatography test (ICT) immunoglobulin G-immunoglobulin M (IgG-IgM) presented the highest sensitivity (100%), whereas the Sh-TSP-2 serum ELISA test had 79.2%. The Sh-TSP-2 urine and serum ELISA tests had the highest specificities among the serological methods (87.5 and 75%, respectively). CRS modelling showed that the ICT IgG-IgM, NovaLisa^® and Sh-TSP-2 serum tests led in sensitivity at 97.1, 88.6 and 71.4%, respectively, with all tests except that the ICT IgG-IgM test having a specificity >90%. Sh-TSP-2 has been validated as a screening tool for patients suspected of having urogenital schistosomiasis. Although commercial serological tests have shown higher sensitivities, Sh-TSP-2 could be valuable for confirming results from tests with lower specificity. Nevertheless, further studies with larger patient cohorts are necessary to fully verify its potential.

Keywords: Schistosoma haematobium; diagnostics; migrants; travellers; urogenital schistosomiasis.

Graphical abstract

Figure 1.

Eosinophilia values in Schistosoma haematobium-infected and -uninfected participants. Red dots/triangles correspond to participants also showing microhaematuria. **P ⩽ 0.005.

Figure 2.

IgG antibody responses to Sh-TSP-2 in serum (A) and urine (B) of screened patients. Orange squares from the S. haematobium negative group (negative by microscopy) correspond to patients shown positive to the Schistosoma ICT IgG–IgM test. Horizontal red dotted line represents test cutoff. **P ⩽ 0.005, ***P ⩽ 0.0005.

Figure 3.

Frequency of recognition patterns for all individuals based on the different reference standards: microscopy, LCA and CRS.