54, days 1–5 after infection). In comparison, the rate of detection of NS1 antigen was 22% for secondary infection and 23% for primary infection (Fisher’s exact test for NS1, p = 0.97 and, mean secondary IgG index = 3.8, mean primary IgG index = 2.1) at ≥11 days after onset of disease. Anti-DENV IgG antibodies levels at 1–5 days after

onset of disease did not appear to inhibit NS1 Ag detection. The results, however, suggest that rise in levels of antibodies may be in part responsible for the lower NS1 detection rates (IgM-NS1 Pearson correlation, r = −0.62, IgG-NS1 Pearson correlation, r = −0.45). Thus, the association between rising levels of IgG, including factors such as IgG in antigenemia clearance and immune complex formation, with lower assay Angiogenesis inhibitor sensitivity needs to be further clarified. The differences between the detection rates in primary and secondary infection for each serotype were not statistically significant (primary and secondary DENV-1, chi-squared, p = 0.07, p = 0.24, p = 0.71, and p = 0.66

for DENV-2, DENV-3, and DENV-4, respectively). The utility of the NS1 antigen ELISA was assessed using limited amounts of serum samples: 5 and 0.5 μL (Table 5). Of 53 confirmed positive samples, 50 (94%) serum samples were positive by NS1 antigen ELISA using 5 μL of sample. When serum samples with a Biorad NS1 index value ≥10 were analyzed, NS1 antigen detection rates were 100% (37/37) using CP-868596 purchase 5 μL of samples and 94% (31/33) with 0.5 μL (Table 5). When serum samples with a NS1 index value <10 were analyzed, detection rates were 81% (13/16) with 5 μL and 0% (0/10) with 0.5 μL. The differences between the NS1 antigen detection rates using 5 μL (1:10 dilution) of sample and undiluted samples were not statistically significant (Fisher's exact test, p = 0.24). In contrast, the differences were significant when 0.5 μL (1:100 dilution) was used (Fisher's exact test, p < 0.01, Table 5). Widespread DENV transmission associated with international travel and urbanization continues to pose a global

threat. As such, in addition to the current DENV diagnostic tools available, there is a tremendous need for reliable and dependable diagnostic tools that are relatively selleck chemical easy to use and that do not require highly skilled personnel or costly equipment. The dengue NS1 antigen ELISA is reported to be a promising tool for early dengue diagnosis.[13] While other investigators have reported the utility of various commercially available NS1 kits as a diagnostic tool for DENV infection,[14, 20-30] it is essential that their performance and utility be evaluated before their use becomes prevalent in different health sectors.[12] To determine the utility of the DENV NS1 assay for laboratory diagnosis of DENV infection of international travelers, we used serum samples from those who returned to Japan from various dengue endemic regions including Asia, Central and South America, Pacific Islands, and Africa.