Fibrin degradation product (FDP) and d-dimer levels | FDP: variable depending on specific test, typically <2.5–10 micrograms/mL (2.5–10 milligrams/L) | FDP test: measures breakdown products from fibrinogen and fibrin monomer | Levels are elevated in diffuse intravascular coagulation, venous thrombosis, pulmonary embolus, and liver disease, and during pregnancy |
d-Dimer: variable depending on specific test, typically <250–500 nanograms/mL (250–500 micrograms/L) | d-Dimer test: measures breakdown products of cross-linked fibrin |
Factor level assays | 60%–130% of reference value (0.60–1.30 units/mL) | Measures the percent activity of a specified factor compared to normal | To identify specific deficiencies and direct therapeutic management |
Protein C level | Variable | Level of protein C in the blood | Vitamin K dependent |
Typically 60%–150% of reference value | Increases with age |
Values higher in males than females |
Deficiency associated with thromboembolism in people <50 y of age |
Protein S level | Variable | Level of protein S in the blood | Vitamin K dependent |
Typically 60%–150% of reference value | Increases with age |
Values higher in males than females |
Deficiency associated with thromboembolism in people <50 y of age |
Factor V Leiden (FVL) | Variable | Screening test looks for activated protein C resistance, and confirmatory test analyzes DNA sequence of factor V gene | FVL not inactivated by activated protein C |
Screening assay uses activated partial thromboplastin time with and without added activated protein C | Heterozygotes have 7× and homozygotes have a 20× increased lifetime risk of venous thrombosis |
Mutation associated with thromboembolism in people <50 y of age |
Antithrombin level | Variable depending on specific test | Measures level of antithrombin in the blood | Not vitamin K dependent; patients with deficiency require higher dosages of heparin for anticoagulation therapy |
Typically 20–45 milligrams/dL (200–450 milligrams/L) | Deficiency associated with thromboembolism in people <50 y of age |
Antiphospholipid antibodies | IgG <23 GPL units/mL and IgM <11 MPL units/mL | Tests for antibodies that bind to phospholipids | Lupus anticoagulant: elevated in systemic lupus erythematosus (SLE) and other autoimmune diseases |
Lupus anticoagulant | Anticardiolipin antibody: elevated in SLE, other autoimmune diseases, syphilis, and Behçet's syndrome |
Anticardiolipin antibody | Increased risk of spontaneous abortions, fetal loss, and fetal growth retardation |
Anti–factor Xa activity | During therapeutic anticoagulant use: 0.7–1.1 units/mL | Inhibition of factor Xa activity | Used to monitor low-molecular-weight heparin therapy, and newer anticoagulants such as apixaban and rivaroxaban |
During prophylactic anticoagulant use: 0.2–0.3 units/mL | May be elevated in renal dysfunction |
Platelet function assay | 88–183 s | Tests for platelet adhesion and aggregation | Affected by uremia, anemia, thrombocytopenia, antiplatelet medications, and von Willebrand's disease |
Variable | Initial test done with epinephrine. A prolonged test is repeated using ADP, and if normal <122 s, indicates probable aspirin effect |
Peripheral blood smear | Qualitative and quantitative based on visualization | Estimates quantity and appearance of platelets, WBCs, and red blood cells | Allows identification of clumped platelets, abnormal cells interfering with coagulation (leukemia) |
Operator dependent |
Dilute Russell viper venom time | 23–27 s | Venom directly activates factor X and converts prothrombin to thrombin when phospholipid and factor V are present | Prolonged in the presence of antiphospholipid antibodies |
Inhibitor screens | Variable | Verifies the presence or absence of antibodies directed against one or more of the coagulation factors | Specific inhibitors: directed against one coagulation factor, most commonly against factor VIII |
Nonspecific inhibitors: directed against more than one coagulation factor; example is lupus-type anticoagulant |
Des-γ-carboxyprothrombin or PIVKA II (protein induced by vitamin K absence or antagonism) test | Variable | Measures inactive under-carboxylated form of prothrombin | Increased in vitamin K–deficient states, such as hemorrhagic disease of the newborn |
Increased in overdoses of warfarin or cholestatic liver diseases that can respond to vitamin K therapy |