Dengue Fever and Tourniquet Test

https://youtu.be/zqQgUNVD-w8

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Dengue fever and tourniquet test

• Dengue fever is a mosquito-borne viral disease that is widespread in tropical and subtropical regions. 
• The World Health Organization has outlined diagnostic criteria for making the diagnosis of dengue infection, which includes the use of the tourniquet test. 
• The tourniquet test is a marker of capillary fragility and it can be used as a triage tool to support diagnostic decision-making during the initial febrile phase which may last 2 to 7 days after the development of fever.

Symptoms and signs of dengue fever

• Dengue fever follows a distinct pattern with three phases: febrile phase, critical phase, and convalescent or recovery phase. 
• During the febrile phase, there is an abrupt onset of fever for 2 to 5 days, along with other symptoms such as headache, muscle, bone, and joint pain, nausea, vomiting, pain behind the eyes, swollen glands, and rash. The fever pattern is classically biphasic or "saddleback", breaking and then returning for 1 or 2 more days. 
• The critical phase usually occurs around the time the fever subsides and lasts for 1 to 2 days. During this phase, there is a risk of developing severe dengue, which can cause serious bleeding, a sudden drop in blood pressure, shock, and death. 
• The convalescent or recovery phase begins after the critical phase and can last for several days to weeks. During this phase, the symptoms gradually improve, and the patient recovers.

Tourniquet test

• The tourniquet test, also known as the Rumpel-Leede or Hess test, is a simple diagnostic tool that can be used to assess capillary fragility.
  
• The test involves inflating a blood pressure cuff on the upper arm to a pressure midway between the systolic and diastolic blood pressure for five minutes. After five minutes, the cuff is deflated and the number of petechiae in a 2.5 cm x 2.5 cm area on the forearm is counted.
  
• A positive tourniquet test is defined as the presence of 10 or more petechiae per 2.5 cm x 2.5 cm area.

Diagnostic accuracy of the tourniquet test

• A systematic review and meta-analysis of diagnostic test accuracy found that the tourniquet test has poor diagnostic performance, with a pooled sensitivity and specificity of 58% and 71%, respectively. However, the tourniquet test is still widely used in resource-poor settings despite currently available evidence demonstrating only a marginal benefit in making a diagnosis of dengue infection alone.

Summary

• The tourniquet test is a simple and inexpensive diagnostic tool that can be used to support diagnostic decision-making during the initial, acute, febrile phase of dengue infection.
  
• However, the test has poor diagnostic performance and should not be relied upon as the sole diagnostic tool for dengue fever.
  
• Other diagnostic tests, such as nucleic acid amplification tests and serological tests, should also be used to confirm the diagnosis of dengue fever.