Evaluation of two commercially available chikungunya virus IgM enzyme-linked immunoassays (ELISA) in a setting of concomitant transmission of chikungunya, dengue and Zika viruses

Abstract

Objective To evaluate the diagnostic performance of the Inbios (Seattle, US) and Euroimmun (Luebeck, Germany) chikungunya virus (CHIKV) IgM enzyme-linked immunoassays (ELISAs). Methods We evaluated the tests’ accuracy on sera from 372 patients enrolled in an acute febrile illness surveillance study performed in Salvador, Brazil from Sept/2014 to Jul/2016, a period of simultaneous CHIKV, dengue (DENV), and Zika (ZIKV) virus transmission. We assessed the sensitivity on acute and paired convalescent sera from RT-PCR-confirmed CHIKV cases (collected at median one and 19 days post-onset of symptoms, respectively), and the specificity on sera of RT-PCR-confirmed DENV and ZIKV cases, and on negative patients. Results The Inbios and Euroimmun tests’ sensitivities for acute samples were 4.0% and 10.3%, while for convalescent samples they were 92.4% and 96.9%, respectively. Overall, Inbios IgM ELISA specificities for acute and convalescent samples were 97.7% and 90.5%, respectively, and Euroimmun specificities were 88.5% and 83.9%, respectively. Conclusions Both tests presented high sensitivity for convalescent samples. However, the Euroimmun test returned more equivocal results and presented a slightly lower specificity, which might result in a higher rate of false positives if the test is used in scenarios of low CHIKV transmission, when the chance of CHIKV infection is lower.