There are many names of capillary fragility tests, it can be HESS test or tourniquet test. But the purpose of the test is the same.

This is also used to diagnose dengue.

Capillary fragility test (tourniquet test) principle

A tourniquet test or Hess test, at 80 mm Hg pressure at the forearm causes obstruction of and obstructs venous blood return raises the blood pressure in the capillaries. This pressure causes the rupture of capillaries and causes petechiae at the antecubital fossa.

Tourniquet test requirements

  1. Hess’s test is simple. We don’t need specific machines or instruments. We need only one thing.
  2. Sphygmomanometer

Hess test procedure (Tourniquet test)

Here is the procedure of the HESS test.

  1. Apply the Sphygmomanometer cuff on arm and inflate it to 80 mm Hg pressure.
  2. Keep this pressure for FIVE minutes.
  3. After five minutes, check the volar surface of the forearm for the appearance of petechiae at the antecubital fossa.
  4. If you found petechiae, count the petechiae in a 3 cm2 area.
  5. If you found twenty (20) petechiae in this area, then the result is positive.

Capillary fragility test (Hess test) purpose

Hess test or capillary fragility test has THREE purposes.

  1. Check the capillary RESISTANCE.
  2. It is used to check the Platelet NUMBER in the blood.
  3. Hess test is used to monitor the platelets FUNCTION in the body.
  4. A tourniquet test is used to diagnose dengue.

Factors affecting capillary fragility test (HESS TEST)

There are two main factors that affect the capillary fragility test.

  1. Time is an important factor. Apply the Sphygmomanometer cuff for only 5 minutes. More than 5 minutes or less than 5 minutes can affect the result.
  2. Sphygmomanometer pressure is also an important factor.80 mm Hg pressure should be applied. More than or less than 80 mm Hg pressure can alter the fragility result.

Hess test positive

If petechiae appear at the antecubital fossa after 80 mm Hg pressure, it means hess tests positive. The patient has a low platelets count or platelets function defects.

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