How long should a dengue tourniquet test be applied?

Answer 1

A blood pressure cuff is inflated to a point between the systolic and diastolic blood pressures for five minutes. The test is positive if there are more than 20 petechiae per square inch (a petechia is a small red or purple spot on the body, caused by a minor hemorrhage).

Answer 2

Tourniquet Test

Answer 3

Dengue haemorrhagic fever (DHF), a public problem in most of the tropical countries of South-East Asia, is diagnosed on the basis of demonstrating an increased capillary permeability and thrombocytopenia with concurrent haemoconcentration. Tourniquet test has been recommended as the initial screening procedure of patients with suspected DHF, particularly grade I DHF. The objective of the present study was to study the value of this test as an indicator of haemorrhagic tendencies in patients of DHF. METHODS: One hundred and ten adult patients hospitalized with DHF during outbreak of DHF in 1996 in north India were prospectively studied. The diagnosis of DHF was considered on the basis of haemoconcentration > 20%, evidence of transudation, or presence of shock along with thrombocytopenia. A tourniquet test was conducted in these cases in the standard method. RESULTS: Of the 110 patients of DHF studied, 62 patients (56.4%) had bleeding but tourniquet test was positive in only half of these patients. Forty eight patients (43.6%) did not have any bleeding and the tourniquet test was positive in only 27% cases. CONCLUSIONS: The tourniquet test was positive in only 39.1% of all DHF cases. It is concluded that a negative tourniquet test may not be sufficient to exclude a diagnosis of DHF in a febrile patient. This necessitates the need for the re-defining the clinical criteria for the diagnosis of DHF, particularly grade I DHF.

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The tourniquet test is frequently positive. A tourniquet test is used to assess if capillaries can withstand increased pressure which is important to assess as the vasculopathy that leads to DSS and DHF which is often first visualized in the form of petechiae. The tourniquet test is assessed by inflating a blood pressure cuff on an arm to above venous pressure (70 mm Hg) for 5 minutes and then relieve the pressure. Inspect the extremity for petechiae. If there are > 2 petechiae then the test is positive. This test does not have high specificity. Interfering factors with this test are women that are premenstrual, postmenstrual and not taking hormones, or those with sun damaged skin, since all will have increased capillary fragility. Large petechiae are associated with thrombocytopenia.