Laboratory diagnosis of Dengue Fever - antibody IgG IgM, antigen NS1
Dengue fever is a common mosquito borne infection in Asia. According to figures from CHP, there has been over 41000 cases confirmed in Thailand and over 1000 cases in Singapore. This first local dengue case of this year has also been also confirmed by CHP on 14/8 and is expected to have more confirmed case in the near future. Although symptoms of first infection is usually mild, subsequent infection with different serotypes of dengue virus may lead to severe dengue which can be fatal. It is therefore important to prevent getting infection and also to diagnose the infection to prevent spreading the virus through subsequent mosquito bites. Apart from clinical signs, dengue fever is confirmed by laboratoy investigation by antibody, antigen and/or DNA detection from patient blood. As soon as one day after onset of symptoms, virus DNA and NS1 antigen are at their highest level which laboratory can test on the patient serum for the presence of DNA and/or NS1 antigen, up to eighteen days. Serum antibody IgM starts to rise as early as three days after virus exposure with an average three to seven days for seroconversion to appear. IgM can stay detectable up to 90 days after viral exposure. IgG is a long last antibody which can be detected up to years. Early detection is important in terms of disease management as well as infection control and NS1 antigen serves as a useful marker for this purpose. A combination of NS1 antigen, IgM antibody and IgG antibody can therefore detect dengue infection from the very beginning up to seroconversion with the presence of IgG.
Although there is no specific treatment for dengue fever, people with suspected dengue infection showing symptoms of high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph modes and rash are adviced to seek medical attention and have the infection confirmed so that patient can receive suitable support care to prevent possible adverse outcome.