Novel Test Device Diagnoses Dengue

The test is based on the capture of specific dengue antibodies using immobilized dengue virus (DENV) serotype 2 antigen and the subsequent detection of the captured immunoglobulin using goat anti-human IgA conjugated to colloidal gold.

Scientist at the Instituto Politécnico Nacional (Mexico City, Mexico) compared the immunochromatographic test device known as the ASSURE Dengue IgA Rapid test with other commercial tests. A total of 225 sera were used for the evaluation; One hundred and seventy-two sera were collected during the years 2009 and 2010 from dengue patients in regional public health diagnosis laboratories as part of the national surveillance program for dengue in Mexico and 47 sera were collected from healthy blood donors.

ASSURE Dengue IgA Rapid Test (MP Diagnostics; Solon, OH, USA) is an indirect solid-phase immunochromatographic assay where antibodies in the test sample (serum, plasma or whole blood) form antibody-antigen complexes with immobilized-antigen on the membrane as the test sample migrates upwards from the sample well. The bound antibody-antigen complexes are subsequently detected by anti-human IgA conjugated to colloidal gold. The control line contains protein L that binds with human IgA and the anti-human IgA-colloidal gold conjugate, and serves as an indication of proper sample addition.

The ASSURE test detected as positive for IgA 105/172 (61.0%) of the dengue sera tested, while the Dengue IgM Capture ELISA (PanBio, Sinnamon Park, Queensland, Australia) detected as positive for IgM, 93/172 (54.1%) of the sera. The overall specificity and sensitivity of the ASSURE test were 85.1% and 61.0%, respectively. The positivity rate for IgA went from 33.3% for sera collected the same day of fever onset to 81.2% for sera collected five days after fever onset. Infections with serotype 2 viruses were detected more efficiently than those with serotype 1 viruses were, and no sera from infections with serotypes 3 and 4 were available. The kit was twofold more efficient at detecting secondary infections than at detecting primary infections.

The authors concluded that the rapid test based on immunochromatography required few facilities to be carried out and are very suitable to be applied on single samples. The implementation of immunochromatographic assays in field locations or point-of-care sites may be a valuable alternative to test for early diagnosis of dengue. The study was published in the February 2012 issue of the journal Diagnostic Microbiology and Infectious Disease.

Related Links:
Instituto Politécnico Nacional
MP Diagnostics
PanBio