Immunoglobulin A-specific capture enzyme-linked immunosorbent assay for diagnosis of dengue fever

Abstract

Dengue fever (DF) is usually diagnosed by testing for dengue virus immunoglobulin M (IgM) by a capture enzyme-linked immunosorbent assay (ELISA) (MAC-ELISA). However, IgM can last for months, and its presence might reflect a previous infection. We have tested the use of anti-dengue virus IgA capture ELISA (AAC-ELISA) for the diagnosis of DF by comparing the results of MAC-ELISAs and AAC-ELISAs for 178 serum samples taken from patients with confirmed cases of DF. IgM appears more rapidly (mean delay of positivity, 3.8 days after the onset of DF) than IgA (4.6 days) but lasts longer; the peak IgA titer is obtained on day 8. The specificity and the positive predictive value of AAC-ELISA are 100%; its sensitivity and negative predictive value (NPV) are also 100% between days 6 and 25 after the onset of DF, but they decrease drastically when data for tests conducted with specimens from the first days of infection are included, because the IgA titers, like the IgM titers, have not yet risen. AAC-ELISA is a simple method that can be performed together with MAC-ELISA and that can help in interpreting DF serology.

FIG. 1

Percentages of positive (▨), indeterminate (░⃞), and negative (□) results for AAC-ELISA (A) and MAC-ELISA (B) for 14 patients from whom sequential sera were available.

FIG. 2

Evolution of the mean ratios of the absorbance for the well containing the serum specimen divided by the mean of the absorbance values for the negative wells for AAC-ELISA (▪) and by the absorbance for the uninfected control well for MAC-ELISA (○) after the onset of DF. The means were determined for 178 reference serum samples and 61 sequential serum samples. Numbers in parentheses represent the numbers of serum samples tested.