Hess test is done to assess -
Bleeding time
Capillary fragility
Clotting time
Prothrombin time
Hess capillary resistance test or tourniquet test is done by tying sphygmomanometer cuff to the upper arm and raising it in between diastolic and systolic pressure for 5 minutes.
Presence of more than 20 petechiae over the cubital fossa is considered a positive test.
The test is positive in increased capillary fragility as well as in thrombocytopenia.