Capillary fragility test

Alternative names:

positive pressure test; tourniquet test

How the test is performed:

A tourniquet or blood pressure cuff is applied to the arm with enough pressure that the venous return of blood is prevented. The resulting increased capillary pressure may cause capillary rupture, which manifests as petechiae (small, purplish areas on the skin).

After 5 minutes, the pressure is released and the number of petechiae in a 2-inch area are counted and classified by a scoring system.

How to prepare for the test:

No special preparation is necessary for the capillary fragility test.

How the test will feel:

There may be some discomfort from the pressure on your arm.

Why the test is performed:

Your health care provider may perform this test to generally evaluate the fragility of your capillary walls, or the deficiency of blood platelets (thrombocytopenia).