Assay of specific factors of coagulation is done in the investigation of inherited and acquired bleeding disorders. For example, tests of factor VIII–related antigen are used in the differential diagnosis of classic hemophilia and von Willebrand disease in cases in which there is no family history of bleeding and bleeding times are borderline or abnormal. A test for ristocetin cofactor is done to help diagnose von Willebrand disease by determining the degree or rate of platelet aggregation that is taking place.

Factor II—prothrombin: 80%–120% of normal

Factor V—labile factor: 50%–150% of normal

Factor VII—stable factor: 65%–140% of normal or 65–135 AU

Factor VIII—antihemophilic factor: 55%–145% of normal or 55–145 AU

Factor IX—Christmas factor: 60%–140% of normal or 60–140 AU

Factor X: 45%–155% of normal or 45–155 AU

Factor XI: 65%–135% of normal or 65–135 AU

Factor XII—Hageman factor: 50%–150% of normal or 50–150 AU

Ristocetin (von Willebrand factor): 45%–140% of normal or 45–140 AU

Factor VIII antigen: 100 μg/L or 50%–150% of normal or 50–150 AU

Factor VIII–related antigen: 45%–185% of normal or 45–185 AU

Fletcher factor (prekallikrein): 80%–120% of normal or 0.80–1.20

1. Draw a 5-mL venous blood sample by the two-tube method and add to a collection tube containing sodium citrate as the anticoagulant. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

2. Cap samples, put on ice, and send to the laboratory as soon as possible.

1. Inherited deficiencies:

   • Any of the specific factors—I, II, V, VII, VIII, IX, X, XI, XII, and XIII—may be deficient on a familial basis.

   • Factor VII is decreased in hypoproconvertinemia (autosomal recessive).

   • Factor VIII is decreased in classic hemophilia A and von Willebrand disease (inherited autosomally).

   • Factor IX is decreased in Christmas disease or hemophilia B (sex-linked recessive).

   • Factor XI is decreased in hemophilia C (autosomal dominant, occurring predominantly in Jewish people).

2. Acquired disorders:

   1. Factor II is decreased in:

      1. Liver disease

      2. Vitamin K deficiency

      3. Oral anticoagulant use (last factor to decrease after starting warfarin therapy)

      4. Normal newborns

      5. Circulating inhibitors or lupus-like anticoagulants

   2. Factor V is decreased in:

      1. Liver disease

      2. Factor V inhibitors

      3. Myeloproliferative disorders

      4. DIC and fibrinolysis

      5. Normal newborns (mildly decreased)

   3. Factor VII is decreased in:

      1. Liver disease

      2. Treatment with coumarin-type drugs (first factor to decrease)

      3. Normal newborns

      4. Kwashiorkor

   4. Factor VIII is increased in:

      1. Late normal pregnancy

      2. Thromboembolic conditions

      3. Liver disease

      4. Postoperative period

      5. Rebound activity after sudden cessation of a coumarin-type drug

      6. Normal newborns

   5. Factor VIII is decreased in:

      1. Presence of factor VIII inhibitors (anticoagulants capable of specifically neutralizing a coagulation factor and thereby disrupting hemostasis), associated with hemophilia A and immunologic reactions, and postpartum

      2. von Willebrand disease

      3. DIC, fibrinolysis

      4. Myeloproliferative disorders

   6. Factor IX is decreased in:

      1. Uncompensated cirrhosis, liver disease

      2. Nephrotic syndrome

      3. Development of circulating anticoagulants against factor IX (rare)

      4. Normal newborns

      5. Dicumarol and related anticoagulant drugs

      6. DIC

      7. Vitamin K deficiency

   7. Factor X is decreased in:

      1. Vitamin K deficiency

      2. Liver disease

      3. Oral anticoagulants

      4. Amyloidosis

      5. DIC

      6. Normal newborns

   8. Factor XI is decreased in:

      1. Liver disease

      2. Intestinal malabsorption (vitamin K)

      3. Occasional development of circulatory anticoagulants against factor IX

      4. DIC

      5. Newborns (do not reach adult levels for up to 6 months)

   9. Factor XII is decreased in:

      1. Nephrotic syndrome

      2. Liver disease

      3. Chronic granulocytic leukemia

      4. Normal newborns

   10. Factor XIII is decreased in:

       1. Postoperative patients

       2. Liver disease

       3. Persistent increased fibrinogen levels

       4. Obstetric complications with hypofibrinogenemia

       5. Acute myelogenous leukemia

       6. Circulating anticoagulants

       7. DIC

Pretest Patient Care

1. Explain test purpose and procedure.

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