In a tourniquet test for dengue, the blood capillaries are examined for their ability to withstand increased pressure. This gives a good indication for assessing the blood vessels and whether it will lead to Dengue Shock Syndrome (DSS) or Dengue Hemorrhagic Fever (DHF). This test involves checking what are known as petechiae, i.e. small red spots under the surface of the skin. These petechiae are formed when blood leaks from capillaries into the skin. Pressing the petechiae does not have any effect on its appearance.
Performing the Dengue Tourniquet Test
The World Health Organisation (WHO) has defined this test as one of the necessary requirements for dengue fever diagnosis. According to WHO, the test is deemed to be positive if 10 or more petechiae are found per square inch. In case of Dengue Haemorrhagic Fever (DHF), the test generally gives a sure positive result with 20 or more petechiae per square inch. Since the test does not have high specificity i.e. ability to confirm the infection, the interfering conditions must be taken into consideration.
Premenstrual women, postmenstrual women who are not taking hormonal supplements, women having skin damaged by sun must not take this test as they have high capillary fragility due to altogether different reasons. Since dengue infection is typical of a tropical and sub-tropical country, the tourniquet test is used to evaluate the possibility of dengue infection immediately in such countries. There are 36 million symptomatic cases of dengue worldwide with 2.1 million severe cases reported in the year 2010. With a tourniquet test, people suspected of having contracted the infection can be immediately hospitalised for treatment and further diagnosis.
Performing the Dengue Tourniquet Test
- Pump up a blood pressure cuff on one of the arm to more than venous pressure (70 mm Hg)
- Keep it for 5 minutes and then ease the pressure.
- Examine the extremity of the pressure for petechiae.
- If there are more than 2 petechiae, the test is positive.
The World Health Organisation (WHO) has defined this test as one of the necessary requirements for dengue fever diagnosis. According to WHO, the test is deemed to be positive if 10 or more petechiae are found per square inch. In case of Dengue Haemorrhagic Fever (DHF), the test generally gives a sure positive result with 20 or more petechiae per square inch. Since the test does not have high specificity i.e. ability to confirm the infection, the interfering conditions must be taken into consideration.
Premenstrual women, postmenstrual women who are not taking hormonal supplements, women having skin damaged by sun must not take this test as they have high capillary fragility due to altogether different reasons. Since dengue infection is typical of a tropical and sub-tropical country, the tourniquet test is used to evaluate the possibility of dengue infection immediately in such countries. There are 36 million symptomatic cases of dengue worldwide with 2.1 million severe cases reported in the year 2010. With a tourniquet test, people suspected of having contracted the infection can be immediately hospitalised for treatment and further diagnosis.
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