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Introduction ⬇

Fibrinopeptides A (FPA) and B are formed by the action of thrombin on fibrinogen; therefore, the presence of FPA indicates that thrombin has acted on fibrinogen.

The measurement is the most sensitive assay done to determine thrombin action. FPA reflects the amount of active intravascular blood clotting; this occurs in subclinical DIC, which is common in patients with leukemia of various types and may be associated with tumor progression. FPA elevations can occur without intravascular thrombosis, decreasing the value of a positive 
test.

Normal Findings ⬆ ⬇

Adults: 0.6–1.9 mg/mL

Procedure ⬆ ⬇

  1. Collect a venous blood sample of 5 mL in special Vacutainer tube containing aprotinin EDTA and thrombin to prevent activation in vitro. Use a two-tube method of draining blood.

  2. Draw the specimen in a prechilled tube and place immediately on ice.

  3. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag. Clean venipuncture and gentle handling of specimen are required. The specimen must be transported to the laboratory within 30 minutes.

Clinical Implications ⬆ ⬇

  1. Increased FPA occurs in:

    1. DIC

    2. Leukemia of various types

    3. VTE

    4. MI

    5. Postoperative patients

    6. Patients with widespread solid tumors, malignancies

  2. Decreased FPA occurs in:

    1. Clinical remission of leukemia achieved with chemotherapy

    2. Therapeutic heparinization

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure.

  2. Avoid prolonged use of tourniquet.

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

Posttest Patient Care

  1. 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.

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

  3. Have the patient resume normal activities.

Interfering Factors ⬆

  1. A traumatic venous puncture may result in falsely increased levels.

  2. The biologic half-life (stable for 2 hours or more) imposes limitations on the interpretation of a negative FPA test.

Clinical Alert

DIC occurs commonly in association with death of tumor cells in acute promyelocytic leukemia. For this reason, heparin is used prophylactically and in association with the initiation of chemotherapy for promyelocytic leukemia. DIC occurs less commonly during the treatment of acute myelomonocytic leukemia and ALL. Evidence of DIC should be sought in every patient with leukemia before initiation of treatment