Evaluation of Serological Diagnostic Assays for Distinguishing Zika From Dengue Virus Infections in Thailand

Zika virus (ZIKV) is a mosquito-borne flavivirus that has recently emerged as a global health threat. The emergence of ZIKV has increased the incidence of neonates born with microcephaly or other neurological syndromes. The majority of ZIKV infections are mild or asymptomatic; however, clinical diagnosis is inaccurate. Moreover, Dengue virus cross-reacts with Zika antibodies, which creates problems for the serological diagnosis of ZIKV infections. Zika serological assays are often performed dismally in dengue-endemic areas because of this phenomenon. In this study, we established a Zika/Dengue ELISA Test to improve the differential diagnosis between Zika and Dengue samples. Sixty Zika-positive samples and 120 controls (20 Primary Dengue samples, 80 Secondary Dengue samples, and 20 healthy serum samples were tested using a ZNS1 and DNS1 Indirect ELISA and a commercial IgG ELISA Kit. Different Zika antigens (EDIII, MR766 NS1 and SV0127 NS1) were tested and ROC curves were compared. Among the antigens tested, NS1 yielded the best diagnostic potential with an AUC range of 0.84–0.88, compared with an AUC of 0.77–0.82 for EDIII. The Zika/Dengue OD Ratio also exhibited the best sensitivity (Sn) and specificity (Sp) (58.3% and 79.2% respectively) among the other parameters tested (Sn = 26.7%–28.3% and Sp = 59.2%–79.3%). It also performed better than the commercial kit, which yielded Sn and Sp values of only 26.7% and 74.2%, respectively. The Zika/Dengue OD Ratio has diagnostic potential and better performance compared with commercial ELISA test kits for detecting Zika infections. The combination of two simple ELISAs may be applied for ZIKV serosurveys and to monitor ZIKV infection during pregnancy to understand the epidemiology, pathogenesis, and complications of ZIKV in DENV-endemic areas.