Diagnostic Accuracy of New Dengue Capture Assay Evaluated

By LabMedica International staff writers
Posted on 09 Apr 2015

Dengue disease has become a major global public health concern, but an ideal diagnostic test that permits early and rapid diagnosis is not yet available, so improving diagnostic performance in this area is a major challenge.

The kinetics of dengue infection in serum is accorded by virus isolation and nucleic acid or antigen detection which are the most specific diagnostic methods during the early acute stage of disease, while serology is often used for diagnosis later in the course of infection.

Image: The Dengue Duo Cassette rapid immunochromatographic test used to detect IgM and high-titer IgG antibodies to dengue virus in human serum, plasma and whole blood (Photo courtesy of Panbio).

Image: An enzyme-linked immunosorbent (ELISA) kit used to detect elevated antibodies to dengue virus (serotypes 1-4) in patients with secondary infection (Photo courtesy of Panbio).

Scientists at the Pasteur Institute (Cayenne, French Guiana) selected 184 sera for evaluation included two groups: a group of 134 sera from confirmed dengue-infected patients and a second group of 50 sera from non-dengue infected patients. Sera were classified according to the onset of fever. Day zero was defined as sera collected within 24 hours after the onset of fever. Detection of specific dengue immunoglobulin M (IgM) was carried out using an in-house IgM capture enzyme-linked immunosorbent assay (MAC-ELISA).

The dengue virus (DENV) nonstructural protein (NS1) antigen was detected using the commercial Platelia Dengue NS1 AG antigen-capture enzyme-linked immunosorbent assay (ELISA) (Bio-Rad Laboratories; Marnes La Coquette, France). The Bio-Rad Platelia Dengue IgA Capture is a microplate immunoassay using immuno-capture format for detection of specific IgA against DENV in human serum or plasma. Detections of specific dengue IgM and IgG were carried out using the Panbio Dengue IgM Capture ELISA and the Panbio Dengue IgG Capture ELISA kits (Panbio; Brisbane, Australia).

Out of the 134 dengue group sera, the IgA index assay detected 124 positive, indicating a sensitivity of 93%. Six sera out of the 50 non-dengue group ones were also found IgA positive, demonstrating a specificity of 88%. Seropositivities for IgA broadly increased from 50% for sera collected three to four days after the onset of fever to 100% for those collected seven days after. The IgA test had very good sensitivity for detecting infections caused by three dengue serotypes (DENV-2, DENV-3, DENV-4, with sensitivities of 100%, 97% and 92% respectively), while its ability to detect infection caused by DENV-1 was significantly less efficient (85%). The IgA assay had a good concordance with the Panbio IgM capture ELISA.

The authors concluded that the Platelia Dengue IgA Capture assay is an acceptable test, with overall sensitivity and specificity of about 90%. The IgA test assay is a more accurate dating of infection when used to measure a good quality serological marker detectable in acute-phase serum and persisting for a shorter period of time than dengue specific IgM allows. The study was published on March 24, 2015, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Pasteur Institute
Bio-Rad Laboratories
Panbio