The prothrombin fragment 1 + 2 (F1 + 2) is the amino terminus fragment liberated from the prothrombin molecule when it is activated by factor Xa to form thrombin. Thrombin may be rapidly inactivated by AT III. Prothrombin F1 + 2, however, has a half-life of about 1.5 hours, making it a useful marker for activated coagulation.
Prothrombin F1 + 2 is used to detect activation of the coagulation system before actual thrombosis occurs. It is used to identify patients with low-grade intravascular coagulation (DIC) and to judge the effectiveness of oral anticoagulant therapy. F1 + 2 levels may assist in the study of the hypercoagulable states and in the assessment of thrombotic risk.
Draw a 5-mL sample of venous blood into a blue-topped (sodium citrate anticoagulant) Vacutainer tube. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.
Use the two-tube technique. (Some methods may use lithium heparin.)
Increased prothrombin F1 + 2 is found in the following:
DIC (early)
Congenital deficiencies of AT III
Congenital deficiencies of protein S and protein C
Leukemias
Severe liver disease
Post MI
Failure to achieve a reduction in prothrombin F1 + 2 levels during oral anticoagulant therapy, despite an adequately prolonged PT, suggests inadequate anticoagulation.
Pretest Patient Care
Explain test purpose and procedure.
Avoid prolonged use of tourniquet.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Monitor for DIC and thrombosis.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.
Have the patient resume normal activities.
Levels will be high in the immediate postoperative period.
Decreased with oral anticoagulants (warfarin)
Decreased in patients treated with AT III