Plasminogen is a glycoprotein, synthesized in the liver, present in plasma. Under normal circumstances, plasminogen is a part of any clot because of the tendency of fibrin to absorb plasminogen from the plasma. When plasminogen activators perform their function, plasmin is formed within the clot; this gradually dissolves the clot while leaving time for tissue repair. Free plasmin also is released to the plasma; however, antiplasmins there immediately destroy any plasmin released from the clot (see Figure 2.3).

This test is done to determine plasminogen activity in persons with thrombosis or DIC. When pathologic coagulation processes are involved, excessive free plasmin is released to the plasma. In these situations, the available antiplasmin is depleted, and plasmin begins destroying components other than fibrin, including fibrinogen, factors V and VIII, and other factors. Plasmin acts more quickly to destroy fibrinogen because of fibrinogen’s instability.

For therapeutic destruction of thrombi, urokinase, a trypsin-like protease purified from urine, may be administered to a patient to activate plasminogen to plasmin and induce fibrinolysis. Streptokinase is another therapeutic agent used for the same purpose.

Plasminogen activity:

• Children and adults: 76%–124% of normal for plasma or 0.76–1.24 fraction of normal

• Newborns: 27%–59% of normal for plasma or 0.27–0.59 fraction of normal

1. Draw a 5-mL venous blood sample to a light blue–topped collection tube containing sodium citrate. Use the two-tube method. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

2. Put the sample on ice and transport to the laboratory immediately.

3. The test must be started within 30 minutes after the blood is drawn.

1. Decreased plasminogen activity occurs in:

   1. Some familial or isolated cases of idiopathic DVT

   2. DIC and systemic fibrinolysis

   3. Liver disease and cirrhosis

   4. Neonatal hyaline membrane disease

   5. Therapy with plasminogen activators

2. Decreased levels of plasminogen or abnormally functioning plasminogen can lead to venous and arterial clotting (thrombosis).

3. Increased plasminogen activity occurs in:

   1. Pregnancy (third trimester)

   2. Regular vigorous physical exercise

Pretest Patient Care

1. Explain test purpose and procedure.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

see Appendix E for drugs that affect test outcomes.