Analysis of a Routinely Used Commercial Anti-Chikungunya IgM ELISA Reveals Cross-Reactivities with Dengue in Brazil: A New Challenge for Differential Diagnosis?

Abstract

In Brazil, chikungunya emerged in 2014, and by 2016, co-circulated with other arbovirosis, such as dengue and zika. ELISAs (Enzyme-Linked Immunosorbent Assays) are the most widely used approach for arboviruses diagnosis. However, some limitations include antibody cross reactivities when viruses belong to the same genus, and sensitivity variations in distinct epidemiological scenarios. As chikungunya virus (CHIKV) is an alphavirus, no serological cross reactivity with dengue virus (DENV) should be observed. Here, we evaluated a routinely used chikungunya commercial IgM (Immunoglobulin M) ELISA test (Anti-Chikungunya IgM ELISA, Euroimmun) to assess its performance in confirming chikungunya in a dengue endemic area. Samples (n = 340) representative of all four DENV serotypes, healthy individuals and controls were tested. The Anti-CHIKV IgM ELISA test had a sensitivity of 100% and a specificity of 25.3% due to the cross reactivities observed with dengue. In dengue acute cases, the chikungunya test showed an overall cross-reactivity of 31.6%, with a higher cross-reactivity with DENV-4. In dengue IgM positive cases, the assay showed a cross-reactivity of 46.7%. Serological diagnosis may be challenging and, despite the results observed here, more evaluations shall be performed. Because distinct arboviruses co-circulate in Brazil, reliable diagnostic tools are essential for disease surveillance and patient management.

Keywords: Brazil; anti-chikungunya IgM ELISA; chikungunya diagnosis; dengue cross-reactivity.

Figure 1

Absorbance values obtained using the Anti-chikungunya IgM ELISA test (Euroimmun) on a panel (n = 340) of dengue, chikungunya and controls. The nonparametric Mann–Whitney U test was used to evaluate differences between optical density (OD) among the dengue and chikungunya groups (Groups A–F) in comparison to the healthy individual group (Group G). **** p < 0.0005, ** p < 0.005, * p < 0.05, (-) represents the mean value for each group and (---) dashed lines, the cut-off interval for the test. The negative (<0.8) and positive (>1.1) cutoff values were determined at a wavelength of 450 nm and a reference value between 620 nm and 650 nm.