- How the diagnosis is made
- 1. Physical examination
- 2. Loop proof
- 3. Rapid test to diagnose dengue
- 4. Isolation of the virus
- 5. Serological tests
- 6. Blood tests
- 7. Biochemical tests
The diagnosis for dengue is made based on the symptoms presented by the person, in addition to laboratory tests, such as blood count, virus isolation and biochemical tests, for example. From the exams, the doctor can check what type of virus and thus indicate the most appropriate treatment for the person. Thus, if a fever occurs, accompanied by two or more of the symptoms mentioned above, it is recommended to go to the emergency room so that diagnostic tests are carried out and, thus, treatment begins.
Dengue is a disease caused by the bite of the infected Aedes aegypti mosquito, which is more common to appear in summer and in more humid regions due to the ease of development of the dengue mosquito. See how to identify the dengue mosquito.
How the diagnosis is made
1. Physical examination
The physical examination consists of the assessment by the doctor of the symptoms described by the patient, being indicative of classic dengue:
- Severe headache; Pain in the back of the eyes; Difficulty moving the joints; Muscle pain throughout the body; Dizziness, nausea and vomiting; Red spots on the body with or without itching.
In the case of hemorrhagic dengue, symptoms can also include excessive bleeding that usually manifests as red spots on the skin, bruising and frequent bleeding from the nose or gums for example.
The symptoms usually appear 4 to 7 days after the bite of the mosquito infected by the virus and begins with a fever above 38ºC, but after a few hours it is accompanied by other symptoms. Therefore, when blood is suspected, it is important to seek medical help so that more specific tests can be done to confirm the diagnosis and start treatment quickly, since in more severe cases the dengue virus can affect the liver and heart. Find out what are the complications of dengue.
2. Loop proof
The snare test is a type of rapid exam that checks the fragility of blood vessels and the tendency to bleed, and is often performed in case of suspected classic or hemorrhagic dengue. This test consists of interrupting the blood flow in the arm and observing the appearance of small red dots, with a greater risk of bleeding the greater the amount of red dots observed.
Despite being part of the tests indicated by the World Health Organization for the diagnosis of dengue, the snare test can provide false results when the person is using medications such as Aspirin or Corticosteroids or is in the pre or post menopause phase, for example. Understand how the loop test is done.
3. Rapid test to diagnose dengue
The rapid test to identify dengue is being increasingly used to diagnose possible cases of infection by the virus, as it takes less than 20 minutes to identify whether the virus has been present in the body and for how long due to the detection of antibodies, the IgG and IgM. That way, it is possible to start treatment more quickly.
However, the rapid test also does not identify the presence of other diseases transmitted by the Dengue mosquito, such as Zika or Chikungunya, and therefore, the doctor may order a normal blood test to identify whether you are also infected with these viruses. The quick test is free and can be done at health centers in Brazil by anyone at any time, as it is not necessary to fast.
4. Isolation of the virus
This test aims to identify the virus in the bloodstream and establish which serotype, allowing the differential diagnosis for other diseases caused by the bite of the same mosquito and which have similar symptoms, in addition to allowing the doctor to start a more specific treatment.
Isolation is done by analyzing a blood sample, which must be collected as soon as the first symptoms appear. This blood sample is sent to the laboratory and, through molecular diagnostic techniques, such as PCR, for example, it is possible to identify the presence of the dengue virus in the blood.
5. Serological tests
The serological test aims to diagnose the disease through the concentration of IgM and IgG immunoglobulins in the blood, which are proteins that have their concentration altered in cases of infection. The concentration of IgM increases as soon as the person is in contact with the virus, whereas IgG increases afterwards, but still in the acute phase of the disease, and remains in high amounts in the blood, being, therefore, a marker of the disease, since it is specific to each type of infection. Learn more about IgM and IgG.
Serological tests are usually requested as a way to complement the virus isolation test and blood should be collected about 6 days after the onset of symptoms, as this makes it possible to check immunoglobulin concentrations more accurately.
6. Blood tests
The blood count and the coagulogram are also tests requested by the doctor for the diagnosis of dengue, especially hemorrhagic dengue. The blood count usually shows varying amounts of leukocytes, and there may be leukocytosis, which increases the amount of leukocytes, or leukopenia, which corresponds to a decrease in the number of leukocytes in the blood.
In addition, an increase in the number of lymphocytes (lymphocytosis) is usually observed with the presence of atypical lymphocytes, in addition to thrombocytopenia, which is when platelets are below 100000 / mm³, when the reference value is between 150000 and 450000 / mm³. Know the blood count reference values.
The coagulogram, which is the test that checks the blood's clotting ability, is usually requested in case of suspected hemorrhagic dengue and an increase in prothrombin time, partial thromboplastin and thrombin time can be observed, in addition to a decrease in fibrinogen, prothrombin, a factor VIII and factor XII, indicating that hemostasis is not happening as it should, confirming the diagnosis of hemorrhagic dengue.
7. Biochemical tests
The main biochemical tests requested are the measurement of albumin and liver enzymes TGO and TGP, indicating the degree of liver impairment and being indicative of a more advanced state of the disease when these parameters.
Usually, when dengue is already at a more advanced stage, it is possible to observe a decrease in the concentration of albumin in the blood and the presence of albumin in the urine, in addition to an increase in the concentrations of TGO and TGP in the blood, indicating liver damage.
