Annually, hemorrhagic Dengue fever becomes more prevalent during rainy months and peaks during October - November. Early signs are not highly specific and can be misdiagnosed. For how many days should a fever last before testing for hemorrhagic Dengue fever should be carried out?
1. Signs of hemorrhagic Dengue fever
Patients with hemorrhagic Dengue fever often have the following signs
- High fever: 39 - 41 Celsius degree, with sudden onset and continuously for 2-7 days.
- Petechiae: small dots of bruising due to bleeding under the skin, may be accompanied by bleeding from the nose, gum line, vomiting blood, bloody or tarry stool, or bruising at the injection site.
- Abdominal pain (due to the liver becoming enlarged)
- Shock: between days 3-6, patients may see improvement regarding fever, but may still be agitated, or somnolent, with blue lips, little urination or defecation. Death can occur suddenly without proper medical intervention.
If children experience high fever for over 2 days, they must receive medical care promptly
2. When to test for hemorrhagic Dengue fever?
Typical signs of hemorrhagic Dengue fever are high fever and petechial rash. The most dangerous point during the course of this disease is between 3-7 days (from symptom onset). So for how many days should a fever last before testing for hemorrhagic Dengue fever begins?
A patient can be tested for hemorrhagic Dengue fever from the third day of fever onset. However, during times of year when hemorrhagic Dengue fever is suspected highly, testing should occur sooner: between 24-48 hours of fever onset. A false negative result is more likely when testing early (meaning the patient should test positive but the test returns a negative result instead)
3. What are tests for hemorrhagic Dengue fever?
Patients suspected to have hemorrhagic Dengue fever will require a complete blood count. This test is for monitoring daily changes in the number of blood cells. Other tests that confirm the presence of an infective agent includes testing for antigen, and antibody of the Dengue virus.
3.1 Complete blood count (CBC)
A typical CBC comes with decreased platelet count. This is due to antibodies made to fight the virus accidentally destroying platelets of the patients, causing a low platelet count. Simultaneously, the Dengue virus can suppress bone marrow function, causing a fall in platelet count temporarily. As platelet count drops, bleeding can occur in a number of ways: petechial rash under the skin, bleeding at the lining of body parts, like the gum line, nose, or at the injection site. More severely, bleeding can occur internally, often presenting as: abdominal pain, vomiting blood, tarry stool, prolonged menstrual bleeding.
High risk patients require bed rest, and must avoid moving around frequently. Medical procedure that can cause injury to blood vessels must be limited (large veins in the neck, groin or under the collarbone may not be used for cannulation). As per the newest guideline of the Vietnam Ministry of Health in 2019, patients with hemorrhagic Dengue fever require platelet transfusion when their platelet count is below 50 g/L and signs of bleeding are observed. Patients without signs of bleeding will only receive transfusion when their platelet count is below 5 g/L.
3.2 Testing for hemorrhagic Dengue fever antigen NS1
This test can be carried out within the first 3 days of suspected hemorrhagic Dengue fever. It is important to note that NS1 antigen concentration tend to decrease after the first 3 days, this means testing after this period can give a false negative result. This means the patient is in fact infected with t he Dengue virus but the test indicates the opposite.
3.3 IgG concentration
To confirm evidence of previous infection, a test for the concentration of IgG can be done. This test does not confirm acute Dengue viral infection as IgG only shows up after 7 days from the point of symptom onset. IgG can protect from Dengue virus for the rest of the patient’s life
3.4 IgM concentration
This test is indicated for patients with fever lasting 3-5 days from time of infection. After progression to t he acute phase of infection, IgM is produced by the body to fight the Dengue virus. As a result, the ability to produce IgM of the patient is a key factor in determining the result of testing.
3.5 Other tests for diagnosis and treatment
- CRP concentration: this is to look for evidence of another bacterial infection acquired due to Dengue viral infection
- Serum albumin: The liver is responsible for making albumin, a protein that maintains oncotic pressure in blood vessels. The liver also makes amino acids that play a role in making protein of cells. Serum albumin is tested when hemorrhagic Dengue fever is suspected to look for signs of capillary leakage, thus helping physicians find appropriate treatment.
- Serum electrolytes: this will determine the concentration of serum K+, Na+, Cl- to see if there is evidence of electrolyte imbalances.
- Kidney function (BUN; Cystatin C; Creatinine, Microalbuminuria): evaluate whether renal complications are involved due to hemorrhagic Dengue fever
- Liver function (serum AST, ALT, GGT): to evaluate whether liver injury due to hemorrhagic Dengue fever is present
Laboratory testing should preferentially be done in a hospital since drawing blood is required. However, many hospitals and clinics now offer services that can take blood sample from patients’ home, making this more convenient for patients. The wait time for test result is the same as that of test done at hospitals. Hemorrhagic Dengue fever is becoming more prevalent, with an increase in hospital admission during rainy months of the year. Close monitoring of symptoms and timely testing for hemorrhagic Dengue fever aids in early detection and finding appropriate treatment.
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