This is an automatically translated article.
The article is professionally consulted by Master, Doctor Tran Thi Vuong - Laboratory Department - Vinmec Hai Phong International General Hospital.
Dengue diagnostic tests help determine the presence of the virus that causes the disease in the blood. The tests commonly used to diagnose dengue are NS1, IgM antibody, and IgG antibody.
1. Types of Dengue Diagnostic Tests
With dengue fever, the patient needs a blood test to look for the dengue virus in the blood. There are 3 indicators of dengue fever corresponding to three types of serological tests to diagnose the etiology:Dengue NS1 antigen test: This test is indicated from the first day to the 5th day of illness . If the patient has been sick for more than 3 days (from the end of the 3rd day onwards), even though the dengue fever is indeed present, the NS1 dengue test result may be negative. This is because the test is based on the virus's antigenic determination mechanism. In the disease stage from day 4, the level of viral antigen in the blood has dropped to low, so sometimes the test will be negative.
IgM antibody test: IgM appears from 4-5 days after fever. The IgM test helps to determine the presence of antibodies against dengue virus during the acute phase of the disease. However, depending on the level of antibody production of each patient, this test result is positive or not.
IgG antibody test: Replace with: In the primary form (first infection with Dengue), IgG appears on days 10-14 and can persist for many years afterwards. In the secondary form (having had dengue before), IgG is already present in the blood and increases in 1-2 days
Thus:
From day 3 to day 5: even if the patient really has dengue fever blood but when the test is more likely to be negative; From day 1 to day 3: if you do IgM test, it will also be negative. If the NS1 test is performed, the ability to make an accurate diagnosis depends on whether the virus concentration in the patient's body is sufficient for detection. In case the viral antigen concentration is too low, the NS1 test result may still be negative; From day 4 onwards: the patient may have to have a daily blood test to have enough data for the doctor to confirm the diagnosis. When dengue virus infection is suspected, all 3 tests, NS1, IgM, and IgG should be performed at the same time to diagnose primary or secondary dengue infection.
If NS1 or and IgM positive, IgG negative: primary dengue infection If NS1 or and IgM positive, IgG positive: secondary dengue infection If both NS1, IgM, IgG negative: not dengue fever. It is important to note the timing of the test to be able to make an accurate diagnosis. And note, each individual's immune response to the virus is different, so the test may need to be repeated many times to confirm the diagnosis.
In addition, a complete blood cell count test (complete blood count test) can be performed to aid in diagnosis, monitor progression and prognosis of the disease. Accordingly, if you see a low platelet count, high hematocrit, it is most likely a sign that the disease is progressing seriously, requiring intervention as soon as possible.
Besides, depending on the situation, the doctor may order to perform some more tests to supplement the diagnosis such as:
Electrolyte test (including Na+, K+, Cl-): to evaluate electrolyte disturbances; Liver function tests (including AST, ALT, GGT): to check liver function, assess damage and detect complications of dengue fever; Albumin test: to assess possible plasma leakage for Dengue hemorrhagic fever, to help early recognition and follow-up when the patient has increased vascular permeability; Renal function test (including indicators such as Urea, Creatinine, Cystatin C, MicroAlbuminuria): to probe kidney function and early kidney damage due to complications of dengue fever; CRP test: to evaluate inflammation, help differentiate the cause of fever and evaluate the phenomenon of superinfection due to dengue fever.
2. The process of taking blood to test for dengue fever
When there are signs of suspected dengue fever, the doctor will order the patient to perform a blood test. The patient does not need to do any special preparation before having a dengue blood test.During the blood draw, the patient is asked to remain still. Blood is taken out intravenously, through a fine needle, and stored in a specialized canister. The entire sampling process usually takes only a few seconds to a few minutes, and the patient may feel a slight sting as soon as the medical staff inserts the tip of the needle into the vein.
Most of the cases where blood is drawn as a diagnostic test for dengue fever does not present a serious risk. Some patients may experience mild bruising at the site of blood collection.
Lấy máu xét nghiệm sốt xuất huyết
3. What do dengue fever test results mean?
After analyzing the dengue test indicators, the patient will receive the results in a few hours depending on the type of test. Test results show whether the patient has dengue fever or not:Positive: This result means that the patient has been infected with dengue virus in the blood; Negative: The patient has not been infected with the virus or the time of testing is not appropriate, or the percentage of virus in the blood is not enough to be detected (false negative). If a patient is suspected of having been exposed to the dengue virus or has symptoms of an infection, talk to your doctor about whether you need to be tested again. In case of receiving a positive dengue fever test result, the doctor will advise and assign the patient a reasonable treatment plan. Currently, there is no cure for dengue fever, but the doctor will provide the necessary information to limit symptoms, including rest and drinking plenty of water to overcome dehydration. In addition, patients can take over-the-counter pain relievers (such as paracetamol) to relieve pain and fever.
In case the test result is positive for dengue fever accompanied by obvious symptoms, the patient may have to be hospitalized for monitoring and treatment. Treatment is usually intravenous (IV) fluids, blood transfusions if the patient has lost a lot of blood, blood pressure monitoring, and other interventions if necessary.
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