Diagnostic accuracy of a rapid E1-antigen test for chikungunya virus infection in a reference setting

Objectives: Rapid diagnostic tests targeting virus-specific antigen could significantly enhance the diagnostic capacity for chikungunya virus infections. We evaluated the accuracy of an immunochromatographic antigen test for diagnosis of chikungunya in a reference laboratory for arboviruses. Methods: An immunochromatographic rapid test that uses mouse monoclonal antibodies as a tracer against the E1-envelope protein of chikungunya (ARKRAY, Inc. Kyoto, Japan) was evaluated. Sensitivity was tested in sera from travellers with RT-PCR confirmed chikungunya virus infection (Eastern/Central/Southern African (ECSA) genotype) (n=9) and from patients diagnosed during the 2014-2015 chikungunya outbreak on Aruba (Asian genotype, n=30). Samples from patients with other febrile and non-febrile illnesses (n=26), sera spiked with Flavivirus and Alphavirus reference strains (n=13, including non-spiked serum), and samples containing other selected pathogens (n=20) were used to test specificity of the E1-antigen test. Results: Sensitivity of the E1-antigen test was 8/9 (88.9%, 95% CI 56.5-98.0) for the ECSA genotype, but only 10/30 (33.3%, 95% CI 19.2-51.2) for the Asian genotype. Overall diagnostic specificity was 49/59 (83.1%, 95% CI 71.5-90.5). Conclusions: The E1-antigen test we evaluated had fair diagnostic sensitivity for ECSA genotype chikungunya, but low sensitivity for Asian genotype, and poor overall specificity. Antibodies that react across genotypes will be required for further development of a rapid test for chikungunya. Performance of new tests should be evaluated against different chikungunya genotypes.