The tourniquet test is a rapid examination that must be done in all cases of suspected dengue, since it allows the identification of the fragility of the blood vessels common to the dengue virus infection.
This test can also be known as a Rumpel-Leede test or simply a capillary fragility test, and is part of the World Health Organization's recommendations for the diagnosis of dengue, although this test is not always positive in people with dengue. Therefore, it is important after a positive result, for a blood test to be carried out to confirm the presence of the virus.
Because it identifies the risk of bleeding, the loop test does not need to be used when there are already signs of bleeding, such as bleeding gums, nose or urine. In addition, the tourniquet test may show false results in situations such as aspirin, corticosteroids, pre-or post-menopausal phase, or when there is a sunburn, for example.
What does this test help to diagnose
The tourniquet test is known mainly to aid in the diagnosis of dengue, however, as it tests the fragility of the blood vessels, it can also be used when you are suspicious of other diseases that can cause bleeding, such as:
- Scarlet fever;
- Liver diseases;
Since the tourniquet test can prove positive in several situations, after knowing the result it is always recommended to do other diagnostic tests, beginning with blood tests, for example.
How is the test done
To do the tourniquet test, a square with an area of 2.5 x 2.5 cm should be drawn on the forearm and then the following steps are done:
- Assess the person's blood pressure with the sphygmomanometer;
- Re-inflate the sphygmomanometer cuff to the mean value between maximum and minimum pressure. To know the mean value, it is necessary to add the Maximum Arterial Pressure with the Minimum Blood Pressure and then divide by 2. For example, if the blood pressure value is 120x80, the cuff should be inflated to 100 mmHg;
- Wait 5 minutes with the cuff inflated at the same pressure;
- Deflate and remove the cuff after 5 minutes;
- Let the blood circulate for at least 2 minutes.
Finally, the amount of red spots, called petechiae, should be evaluated inside the square on the skin to know the result of the test.
How to interpret the results
The tourniquet test is considered positive when more than 20 red dots appear within the square marked on the skin. However, a result with 5 to 19 spots may already indicate suspicion of dengue, and other tests should be done to help confirm whether or not you are infected.
It is important to remember that the examination can give a false negative result even in people who have the disease, so if there is suspicion through the symptoms, the doctor should ask for other evaluations to confirm. In addition, it may be positive in other diseases that cause capillary fragility and risk of bleeding, like problems that compromise immunity, genetic diseases or even, use of medications such as aspirin, corticosteroids and anticoagulants, for example.
Therefore, you should take into account that this test is not specific and should be done only to aid in the diagnosis of dengue.