Laboratory diagnosis of dengue infection

Pathology laboratories may adopt a) antigen detection or b) antibody detection methods to assist the diagnosis of dengue infection. The method of choice depends largely on the nature of the specimen and the time of collection of specimen in relation to onset of symptoms. The patient is usually viraemic for 5-7 days post onset of symptoms. Therefore a specimen collected in this interval should be examined for virus or viral antigen. Current methods employed include virus isolation in cell culture or antigen capture ELISA. The inherent problems of lack of sensitivity of the ELISA and time delay for virus isolation should be circumvented by the future use of the polymerase chain reaction to detect viral nucleic acid in clinical specimens. Serum specimens collected later than I week post onset of symptoms should be examined for the presence of specific antibodies. However the production of cross reactive antibodies in flavivirus infections often complicates the serological diagnosis. Traditionally haemagglutination inhibition assays have been used to demonstrate a significant (4 fold) rise between acute and convalescent serum specimens. Current trends toward rapid diagnosis using a single specimen have led to the adoption of lgM capture ELISA protocols. This assay lacks the specificity of both the HI and neutralization test but has proven a useful screening test to detect flavivirus IgM.