Standard Coagulation Profile Components
A standard coagulation profile includes prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen level, and platelet count, which should be measured early and repeatedly to detect coagulopathy. 1, 2
Core Components of Coagulation Profile
Primary Tests
Prothrombin Time (PT):
- Evaluates the extrinsic and common pathways of coagulation
- Assesses factors VII, X, V, II, and fibrinogen
- Prolonged in liver disease, vitamin K deficiency, and warfarin therapy 2
Activated Partial Thromboplastin Time (APTT):
- Evaluates the intrinsic and common pathways of coagulation
- Assesses factors XII, XI, IX, VIII, X, V, II, and fibrinogen
- Prolonged in hemophilia, heparin therapy, and lupus anticoagulant 2
Fibrinogen Level:
- Usually measured by Clauss method or derived fibrinogen
- Low levels increase bleeding risk
- Included in 90% of first-line testing according to international guidelines 1
Platelet Count:
- Essential component of hemostasis
- Thrombocytopenia (<150,000/μL) increases bleeding risk
- Critical when <50,000/μL 2
Additional Tests Sometimes Included
Depending on clinical context, these tests may also be included in an expanded coagulation profile:
- D-dimer: Fibrin degradation product used to rule out venous thromboembolism 2
- Thrombin Time: Measures time for conversion of fibrinogen to fibrin 1
- Factor Assays: Specific factor levels (II, V, VII, VIII, IX, X, XI, XIII) when deficiency is suspected 1
Advanced Coagulation Testing
When standard coagulation profiles are insufficient, these specialized tests may be ordered:
- Viscoelastic Testing: Thromboelastometry/thromboelastography to assess clot formation in real-time 1
- Platelet Function Testing: Light transmission aggregometry to evaluate platelet function 1
- Bleeding Time: Though less commonly performed now, may still be available in some institutions 3
Clinical Significance and Interpretation
- PT and APTT only monitor the initiation phase of blood coagulation (first 4% of thrombin production) 1
- Normal PT/APTT doesn't necessarily mean normal overall coagulation status 1
- Viscoelastic methods provide faster results (30-60 minutes quicker) than conventional tests 1
- Early variables of clot firmness from viscoelastic testing predict need for massive transfusion, thrombotic events, and mortality 1
Common Pitfalls
- Relying solely on PT/APTT: These tests only assess the initiation phase of coagulation 2
- Timing issues: Sample collection timing and processing can affect results 2
- Medication effects: Many drugs can alter coagulation test results 2
- Pre-analytical variables: Improper sample collection (e.g., underfilled tubes) can falsely prolong results 4
By understanding the components of a coagulation profile and their clinical significance, clinicians can better interpret results and make appropriate treatment decisions for patients with suspected bleeding disorders or those requiring anticoagulation monitoring.