Human serum test region Dengue Infection earlier diagnosis visible pink line antigen antibodies Dengue NS1 Antigen Principle Advantage vitro diagnostic use qualitative detection Dengue NS1 Ag card test Dengue Ns1 Ag Rapid test kit J MitraAdvantage Dengue NS1 Ag Card immunochromatographic test principle anti-dengue NS1 gold colloidal conjugate antibody-antigen-antibody gold colloid forms rapid solid phase Immuno-chromatographic test