Evaluation of an enzyme immunoassay for detection of dengue virus NS1 antigen in human serum

Abstract

We evaluated a one-step sandwich-format microplate enzyme immunoassay for detecting dengue virus NS1 antigen (Ag) in human serum by use of Platelia Dengue NS1 Ag kits (Bio-Rad Laboratories, Marnes La Coquette, France). We collected 299 serum samples from patients with dengue disease and 50 serum samples from patients not infected with dengue virus. For the 239 serum samples from patients with acute infections testing positive by reverse transcription-PCR and/or virus isolation for one of the four dengue virus serotypes, the sensitivity of the Platelia Dengue NS1 Ag kit was 88.7% (95% confidence interval, 84.0% to 92.4%). None of the serum samples from patients not infected with dengue virus tested positive with the Platelia Dengue NS1 Ag kit. A diagnostic strategy combining the Platelia Dengue NS1 Ag test for acute-phase sera and immunoglobulin M capture enzyme-linked immunosorbent assay for early-convalescent-phase sera increased sensitivity only from 88.7% to 91.9%. Thus, NS1 antigen detection with the Platelia Dengue NS1 Ag kit could be used for first-line testing for acute dengue virus infection in clinical diagnostic laboratories.

Figures

FIG. 1.

Platelia Dengue NS1 Ag test results for control patients and for dengue-positive patients (confirmed by RT-PCR and/or viral culture) are shown. The y axis indicates ratio = S/CO, where S is the obtained OD and CO is the mean cutoff value of the OD for the cutoff control duplicates provided in the kit. In this figure, the ratio values are expressed as log10 values and the dashed-dotted line indicates the cutoff value, set to 1 (giving 0 following the logarithmic transformation used to plot the figure). The box indicates statistical values. The boundary of the box closest to the x axis indicates the 25th percentile, a line within the box marks the median, and the boundary of the box farthest from the x axis indicates the 75th percentile. Whiskers above and below the box indicate the 90th and 10th percentiles. The outlying points (○) have also been plotted on the figures.

FIG. 2.

MAC-ELISA results for control patients and for dengue patients (confirmed by RT-PCR and/or viral culture) are shown. The y axis indicates the OD values, expressed as natural logarithms (ln), and the dashed-dotted line indicates the cutoff value of the assay, set to 0.5 (giving −0.69 after natural log transformation). The ODs for dengue MAC-ELISA were not available for the serum samples from the 20 patients with recent yellow fever. Box plot details are described in the legend for Fig. 1.