From the Guidelines
Clotting factor studies are a crucial component of diagnosing and managing bleeding disorders, particularly hemophilia A and B, and should be performed using a combination of tests, including Prothrombin Time (PT), Activated Partial Thromboplastin Time (aPTT), Fibrinogen level, and individual factor assays, such as Factor VIII and Factor IX, as recommended by the International Society on Thrombosis and Haemostasis 1. The most common clotting factor studies include:
- Prothrombin Time (PT) and International Normalized Ratio (INR)
- Activated Partial Thromboplastin Time (aPTT)
- Fibrinogen level
- Individual factor assays (e.g., Factor VIII, Factor IX) To perform these tests:
- Collect blood in a blue-top tube containing sodium citrate
- Process the sample within 4 hours of collection
- Interpret results in conjunction with clinical presentation Normal ranges vary by laboratory, but general guidelines are:
- PT: 11-13 seconds
- INR: 0.8-1.2
- aPTT: 25-35 seconds
- Fibrinogen: 200-400 mg/dL Abnormal results may indicate:
- Liver disease
- Vitamin K deficiency
- Disseminated intravascular coagulation (DIC)
- Specific factor deficiencies (e.g., hemophilia)
- Effectiveness of anticoagulant therapy According to a recent study published in the Journal of Thrombosis and Haemostasis, the use of extended half-life recombinant FVIII and FIX products has been shown to be effective in preventing bleeding in individuals with hemophilia A and B, but may require adjustments in laboratory assays to accurately measure FVIII/IX activity 1. In individuals with severe hemophilia A, prophylaxis with low-dose (10 IU/kg 2-3 times per week) FVIII concentrate is an effective alternative form of prophylaxis when intermediate- or high-dose options are not available, as demonstrated by studies such as Verma et al. and Chozie et al. 1. The choice of clotting factor concentrate and prophylaxis regimen should be guided by availability, resources, costs, values, and preferences, and should be individualized based on the patient's specific needs and clinical presentation, as recommended by the International Society on Thrombosis and Haemostasis 1.
From the FDA Drug Label
7.2 Drug-Laboratory Test Interactions HEMLIBRA restores the tenase cofactor activity of missing activated factor VIII (FVIIIa). Coagulation laboratory tests based on intrinsic clotting (i.e., aPTT) measure the total clotting time including time needed for activation of FVIII to FVIIIa by thrombin. Such intrinsic pathway-based tests will yield overly shortened clotting times with HEMLIBRA, which does not require activation by thrombin The overly shortened intrinsic clotting time will then disturb all single-factor assays based on aPTT, such as the one-stage FVIII activity assay; however, single-factor assays utilizing chromogenic or immuno-based methods are unaffected by HEMLIBRA and may be used to monitor coagulation parameters during treatment
Clotting factor studies refer to coagulation laboratory tests that measure the activity of specific clotting factors, such as:
- Intrinsic clotting tests (e.g., aPTT)
- Single-factor assays (e.g., one-stage FVIII activity assay)
- Chromogenic assays
- Immuno-based assays These tests are used to monitor coagulation parameters and detect abnormalities in clotting factor activity 2.
From the Research
Clotting Factor Studies
Clotting factor studies refer to a series of tests used to evaluate the coagulation pathway, including the intrinsic and extrinsic pathways, and the common pathway. These tests are essential in diagnosing and monitoring coagulation disorders, such as hemophilia, von Willebrand disease, and thrombophilia.
Types of Clotting Factor Studies
- Activated Partial Thromboplastin Time (APTT) testing: used to evaluate the intrinsic and common pathways of coagulation 3, 4, 5, 6
- Prothrombin Time (PT) testing: used to evaluate the extrinsic and common pathways of coagulation 4, 5, 7
- Mixing studies: used to differentiate between factor deficiencies and inhibitors 6
- Factor activity assays: used to measure the activity of specific clotting factors 5
Applications of Clotting Factor Studies
- Diagnosis and monitoring of coagulation disorders, such as hemophilia and von Willebrand disease 3, 4, 5
- Monitoring of anticoagulant therapy, such as warfarin and heparin 3, 4, 5
- Evaluation of bleeding disorders, such as thrombocytopenia and platelet function disorders 4, 5
- Screening for thrombophilia and thrombotic disorders 5