What is Dengue Fever Testing?
Dengue fever is a mosquito-borne disease that occurs in tropical and subtropical areas of the world. Mild dengue fever causes a high fever, rash, and muscle and joint pain. A severe form of dengue fever, also called dengue hemorrhagic fever, can cause severe bleeding, a sudden drop in blood pressure (shock) and death.
Diagnosing dengue fever can be difficult, because its signs and symptoms can be easily confused with those of other diseases — such as malaria, leptospirosis and typhoid fever.
Dengue fever testing is used to determine whether a person with signs and symptoms and recent potential exposure has been infected with the dengue virus.
Why is Dengue Fever Testing performed?
Testing may be ordered when individuals have signs and symptoms associated with dengue following travel to tropical locations where the dengue virus is present. Some of the main signs and symptoms include:
- Sudden high fever (40°C)
- Severe headache or pain behind the eyes
- Joint, muscle and/or bone pain
- Gum and nose bleeds
- Easy bruising
- Low white blood cell count
Molecular testing is ordered within one week of the onset of symptoms to detect an acute infection, while antibody testing may be ordered more than 4 days after symptoms appear. If antibody testing is performed, an additional blood sample may be collected after two weeks of symptoms to determine if the antibody level is rising.
What should I know before receiving Dengue Fever Testing?
Antibody tests for dengue fever can be positive if a person is infected with another arbovirus such as West Nile virus. A healthcare practitioner will consider a person’s test results, medical history, and recent travel history in making a diagnosis.
No laboratory test can predict whether or not the infection will progress to the more severe form, but those who have been previously infected with dengue are at an increased risk for developing severe dengue during the second infection.
How to prepare for Dengue Fever Testing?
This test doesn’t require any specific preparation. If you have any concern, don’t hesitate to consult with your doctor.
What happens during Dengue Fever Testing?
Dengue fever testing follows the procedure of a standard blood test, meaning a blood sample will be taken for analysis in the lab.
Two primary types of testing are available:
- Molecular testing (polymerase chain reaction, PCR)—this type of test detects the genetic material of the dengue virus in blood within the first week after symptoms appear (fever) and can be used to determine which of the 4 serotypes is causing the infection. One type of Real Time RT-PCR test can detect dengue and the two other mosquito-borne viruses, Zika and chikungunya, and distinguish between the three. Only certain public health laboratories are able to provide the test after verifying that they can successfully perform the assay. Though the test is not available in hospitals or clinics, healthcare practitioners are able to order it through their state and local public health departments. Results can take from four days to two weeks, according to the Centers for Disease Control and Prevention (CDC). Molecular tests of blood are not likely to detect the virus after 7 days of illness. If the result of a PCR test is negative, an antibody test can be used to help establish a diagnosis, according to the CDC.
- Antibody tests—these tests are primarily used to help diagnose a current or recent infection. They detect two different classes of antibodies produced by the body in response to a dengue fever infection, IgG and IgM. Diagnosis may require a combination of these tests because the body’s immune system produces varying levels of antibodies over the course of the illness. IgM antibodies are produced first and tests for these are most effective when performed at least 7-10 days after exposure. Levels in the blood rise for a few weeks, then gradually decrease. After a few months, IgM antibodies fall below detectable levels. IgG antibodies are produced more slowly in response to an infection. Typically, the level rises with an acute infection, stabilizes, and then persists long-term. Individuals who have been exposed to the virus prior to the current infection maintain a level of IgG antibodies in the blood that can affect the interpretation of diagnostic results.
What happens after Dengue Fever Testing?
This test doesn’t require any special aftercare. After the test, you may resume your daily activities unless instruced otherwise by your doctor.
If you have any questions about the Dengue Fever Testing, please consult with your doctor to better understand your instructions.
Explanation of results
What do my results mean?
Molecular testing—a PCR test that detects the presence of the virus itself is generally considered the most reliable means of diagnosis. A positive result from a PCR is considered conclusive. A negative result on a PCR test may indicate that no infection is present or that the level of virus is too low to detect, as may happen if the test was performed after the 7-day window during which the virus is present in the sample collected for this test. A negative PCR result is followed by antibody testing.
Antibody testing—antibody tests may be reported as positive or negative, or may be reported as an antibody titer with an interpretation of which type(s) of antibody (IgG or IgM) is present.
Positive IgM and IgG tests for dengue antibodies detected in an initial blood sample mean that it is likely that the person became infected with dengue virus within recent weeks. IgM antibody tests can be positive if a person has been infected with a similar virus, such as chikungunya (called cross-reaction). If an initial IgM antibody test is positive, a second test called the Plaque Reduction Neutralization Test (PRNT) is used to confirm the presence of antibodies to dengue virus and to help rule out other viral infections.
If the IgG is positive but the IgM is low or negative, then it is likely that the person had an infection sometime in the past. If the dengue IgG antibody titer increases four-fold or greater (e.g., titer of 1:4 to a titer of 1:64) between an initial sample and one taken 2 to 4 weeks later, then it is likely that a person has had a recent infection.
Negative tests for IgM and/or IgG antibodies may mean that the individual tested does not have a dengue infection and symptoms are due to another cause, or that the level of antibody may be too low to measure. The person may still have a dengue infection – it may just be that it is too soon after initial exposure to the virus to produce a detectable level of antibody.
Depending on the laboratory and hospital, the normal range for Dengue Fever Testing may vary. Please discuss with your doctor any questions you may have about your test results.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: November 6, 2018 | Last Modified: November 6, 2018