A functional test of primary hemostasis can be measured by:

Platelet function is measured by bleeding time (normally 2-7 min), which is a functional test of primary hemostasis. The activated paial thromboplastin time, normally 22-36 sec, is the clotting time measured after addition of phospholipid to recalcified plasma that has been preincubated with paiculate material to initiate activation of the contact system (intrinsic pathway of blood coagulation cascade). The prothrombin time (PT) is the clotting time measured after addition of tissue thromboplastin to recalcified plasma (normal approximately 11-14 sec). The PT measures the activity of the extrinsic and common pathways. The platelet count, normally 150,000-400,000/mL, is determined as pa of an automated blood count. Fibrinogen concentration is frequently estimated from clotting time of diluted plasma after addition of excess thrombin. Ref: Palis J., Segel G.B. (2010). Chapter 6. Hematology of the Fetus and Newborn. In J.T. Prchal, K. Kaushansky, M.A. Lichtman, T.J. Kipps, U. Seligsohn (Eds),Williams Hematology, 8e.