Collaborative study for the characterization of a chikungunya virus RNA reference reagent for use in nucleic acid testing

Background and Objectives: Infections with the mosquito-borne chikungunya virus (CHIKV) can cause febrile illness or be asymptomatic. Laboratory diagnosis of CHIKV is often made with laboratory-developed nucleic acid amplification technology (NAT) assays because there are no U.S. Food and Drug Administration (FDA)-approved diagnostic or blood screening assays. We aimed to produce a well-characterized CHIKV RNA reference reagent (CHIKV-RR) for use in NAT assays. Materials and Methods: A CHIKV RNA-RR consisting of cell culture-grown, heat-inactivated CHIKV diluted in human plasma was assessed by 8 laboratories in a collaborative study. The participants were asked to test the CHIKV-RR using their NAT assay(s) by qualitative testing (determination of RNA end-point by testing log and half-log dilutions followed by calculation of estimated NAT-detectable units/ml, after adjustment for the sample volume used for testing), and by quantitative testing, when available. Results: Results from the testing showed that the CHIKV-RR had an estimated overall mean of 7·56 log₁₀ detectable units/ml, ranging from 6·2 log₁₀ to 8·6 log₁₀. Conclusions: The Center for Biologics for Evaluation and Research/FDA CHIKV RNA-RR for NAT was established with a concentration of 7·56 log₁₀ detectable units/ml.