LABORATORY DIAGNOSIS OF DENGUE VIRUS INFECTIONS

Dengue diagnosis was one of the topics discussed at "the adult dengue" presentations. In this paper, a review is presented focusing on the main challenges of dengue laboratory diagnosis. Accurate and efficient diagnosis of dengue is important for clinical care, surveillance support, pathogenesis studies, and vaccine research. Laboratory diagnosis is also important for case confirmation. Laboratory dengue diagnosis can be performed through virus isolation, genome and antigen detection and serological studies. For virus detection, dengue viremia is short, usually observed two or three days before onset of fever and lasts four to five days later. Therefore, samples for virus detection must be taken in the first four to five days of the disease during febrile phase. In recent years, PCR (polymerase chain reaction) has become an important tool as a quick method for diagnosis of dengue, another is detection of NS1 antigen, using commercial ELISA kit. Serological studies, for primary infection, the dominant immunoglobulin isotype is IgM, anti-IgM may appear during febrile phase (50% of cases), the other half, it appears within 2-3 days of defervescence. Once detectable, IgM levels rise quickly and appears to peak about 2 weeks after the onset of symptoms, then they decline to undetectable level over 2-3 months. Anti-IgG appears shortly afterwards with very low level. The physiological definition of a primary infection is therefore characterized by a high molar fraction of anti-dengue IgM and low molar fraction of IgG. Secondary dengue infections are characterized by a rapid increase in IgG antibodies, anti-dengue IgM appears in most instances, the level are dramatically lower.