capillary fragility test; tourniquet test

Epidemiology

• rarely performed

Indications

• assessment of platelet-vessel wall interactions

Principle

• increasing the intravascular pressure by inflation of a blood pressure cuff results in gaps between capillary endothelial cells
• extravasation of erythrovytes does not normally occur due to occlusion by platelets
• petechiae form if platelets are decreased or dysfunctional

Procedure

• with the patient supine, a blood pressure cuff (on upper arm) is inflated to the midpoint between the systolic blood pressure & diastolic blood pressure (< 100 mm Hg) with the pressure maintained for 5 minutes
• the cuff is removed & the arm raised into the air for 1-2 minutes
• petechiae on the arm is a positive test

More general terms

• clinical procedure

Additional terms

• capillary fragility