Dengue fever is a viral disease that is primarily transmitted through the bite of infected mosquitoes. It is a significant public health concern in Bangladesh from June to August. However, in some years, it lasted up to December. The symptoms of dengue can range from mild to severe and can include high fever, severe headache, joint and muscle pain, rash, nausea, and vomiting. Let's take a look at the Dengue tests.

What is a Dengue Test?

A Dengue test refers to a diagnostic procedure performed to determine the presence of the dengue virus or antibodies against the virus in an individual's blood sample. These tests play a crucial role in identifying and confirming dengue infection. Early detection of dengue is crucial for effective management and prevention of severe complications. Several methods are available to detect dengue infection. The most commonly used diagnostic tests in Bangladesh include Polymerase chain reaction (PCR) and NS1 antigen test.

PCR

PCR (Polymerase Chain Reaction) Dengue test is a molecular diagnostic test used to detect the presence of the dengue virus in a person's blood sample. This test is highly sensitive and specific, allowing for the accurate identification of the dengue virus and its serotypes.

Read more: Food, Drinks during Dengue: What to consume, what to avoid

The PCR Dengue test works by amplifying and detecting the viral genetic material, specifically the viral RNA, present in the blood sample. The test utilizes specific primers that target regions of the dengue virus genome. Through a series of temperature cycles, the PCR machine amplifies the targeted viral RNA, making it detectable.

However, the PCR dengue test is particularly useful during the early stages of infection when the virus is actively replicating in the body. It can detect the virus within seven days of symptom onset, providing a rapid diagnosis. This early detection is crucial for appropriate medical intervention, monitoring, and implementation of preventive measures.

The test is recommended when an individual presents with symptoms consistent with dengue fever, such as high fever, severe headache, joint and muscle pain, and rash. Since these symptoms can also be associated with other viral infections, the PCR Dengue test helps confirm whether dengue is the cause. However, the PCR test is more costly than the NS1 test. Hence, Bangladeshi hospitals use the NS1 antigen test.

Read more: Dengue vs. Severe Dengue: Causes, Symptoms, Treatment, Prevention

NS1

The NS1 Dengue test is a diagnostic test used to detect the presence of the dengue virus in the blood. NS1 stands for "nonstructural protein 1," which is a protein produced by the dengue virus during infection. The test detects the presence of this protein, indicating an active dengue infection.

The NS1 Dengue test is typically used during the acute phase of the infection, which is usually within the first 4-5 days of illness onset. The test is particularly useful because it can detect the virus even before the body has produced antibodies against it. In most cases, the test comes positive in the first 48 hours.

Therefore, NS1 antigen should be tested on the first day of fever. After that, the probability of getting positive decreases from the 3rd day. If NS1 is positive after five days of fever in a dengue patient, it indicates acute dengue. So this makes it a valuable tool for the early diagnosis and management of dengue fever.

Read more: How to protect yourself and your family from Dengue fever

It's important to note that a negative NS1 test result does not necessarily rule out dengue infection. It is because the test may be negative if the specimen is collected immediately following dengue virus exposure or after the acute phase of the infection has passed. In such cases, additional tests, such as those detecting dengue-specific antibodies, may be required for a definitive diagnosis.

If individuals receive negative NS1 test results, it is advisable to conduct further testing to check for the presence of dengue IgM antibodies. This additional test helps determine if there has been recent exposure to the dengue virus.

NS1 antigen test costs Tk. 100 in government hospitals and Tk. 300 in private hospitals. Further, CBC and IgM tests cost Tk 250 at government hospitals.

Read more: Dengue Fever: Symptoms, diagnosis, treatment, prevention

Verdict

Both PCR and antigen tests can be useful for diagnosing dengue infection, depending on the circumstances. PCR tests are generally considered more accurate but may be more expensive and require specialized equipment.

Antigen tests, on the other hand, are more accessible and affordable but may have slightly lower sensitivity and specificity, and a negative result does not necessarily rule out dengue infection. In some cases, doctors may use a combination of tests, including antibody tests, to confirm a dengue diagnosis.

The accurate and timely diagnosis of dengue infection is crucial to prevent severe complications. Doctors should consider the patient's symptoms and illness onset and determine whether to test PCR or NS1 Antigen.

Read more: Leaflet distribution program in DSCC to raise dengue awareness