What tests and treatment are recommended for an initial blood clotting workup?

Initial Blood Clotting Workup

For patients presenting with bleeding, order a complete blood count with platelets and peripheral smear, PT/INR, aPTT, and fibrinogen level as your first-line laboratory tests. 1

First-Line Laboratory Tests

The American Society of Hematology establishes a clear standard panel for initial bleeding evaluation:

• Complete blood count (CBC) with platelets and peripheral blood smear to evaluate for thrombocytopenia and abnormal platelet morphology 1
• Prothrombin time (PT/INR) to assess the extrinsic coagulation pathway 2, 1
• Activated partial thromboplastin time (aPTT) to evaluate the intrinsic coagulation pathway 2, 1
• Fibrinogen level (Clauss method) to assess for fibrinogen disorders 2, 1

These four tests form the foundation of coagulation assessment and should be ordered together as an initial panel. 1 The European guideline on major trauma emphasizes early and repeated measurement of these parameters, as they provide rapid detection of post-traumatic coagulopathy. 2

Additional First-Line Tests for Specific Presentations

If the patient has mucocutaneous bleeding (nosebleeds, gum bleeding, heavy menstrual bleeding, easy bruising):

• Von Willebrand factor antigen (VWF:Ag) 1, 3
• VWF ristocetin cofactor activity (VWF:RCo) 1, 3
• Factor VIII coagulant activity 1, 3
• ABO blood group testing (Type O patients have 60-70% lower VWF levels than type AB) 1
• Iron studies to evaluate for chronic blood loss 1

The National Heart, Lung, and Blood Institute recommends these three VWF tests be ordered together when von Willebrand disease is suspected, as no single test can screen for all forms. 3

Point-of-Care Testing

If available, use viscoelastic methods (thromboelastography/TEG or rotational thromboelastometry/ROTEM) to assist in characterizing coagulopathy and guiding hemostatic therapy. 2

Viscoelastic testing provides several advantages:

• Significantly shorter turnaround time (30-60 minutes faster than conventional laboratory testing) 2
• Better prediction of massive transfusion needs, thrombotic events, and mortality 2
• Real-time assessment of clot formation and fibrinolysis at the bedside 2

The World Society of Emergency Surgery recommends point-of-care tests during interventions for life-threatening hemorrhage or emergency neurosurgery. 2

Second-Line Testing (When First-Line Tests Are Normal But Bleeding History Is Convincing)

• Intrinsic pathway factors (FVIII, FIX, FXI assays) 1
• Extrinsic pathway factors (FII, FV, FVII, FX assays) 1
• Factor XIII activity (frequently overlooked but clinically important) 1
• Light transmission aggregometry with multiple agonists (ADP, collagen, epinephrine, ristocetin, arachidonic acid) for mucocutaneous bleeding 1
• Platelet flow cytometry to evaluate platelet surface glycoproteins and activation markers 1
• VWF multimer analysis if the ratio of VWF:RCo to VWF:Ag is below 0.5-0.7 1, 4

Critical Timing and Monitoring Considerations

Repeat coagulation tests early and frequently in bleeding patients. 2 The European guideline emphasizes that single measurements are insufficient—serial monitoring detects evolving coagulopathy. 2

For trauma patients specifically:

• Measure PT, aPTT, fibrinogen, and platelets immediately upon arrival and repeat frequently 2
• Maintain platelet count >50,000/mm³ for life-threatening hemorrhage (higher for neurosurgery) 2
• Maintain PT/aPTT <1.5 times normal control during interventions 2

Common Pitfalls to Avoid

Do not rely on PT and aPTT alone to assess bleeding risk. These tests monitor only the initiation phase of coagulation (the first 4% of thrombin production), and patients can have normal PT/aPTT with significant coagulation abnormalities. 2, 5 This is why fibrinogen and platelet measurements are equally essential. 2

Do not order bleeding time or PFA-100 as routine screening tests. Despite their availability, these tests have conflicting data regarding sensitivity and specificity and are not recommended for routine use. 1, 3

Do not order VWF multimer analysis as part of initial screening. This complex test should be reserved for reflex testing when initial results show a discrepant VWF:RCo to VWF:Ag ratio. 1, 3

Consider timing factors that affect results:

• Stress, exercise, and inflammation falsely elevate VWF levels 3
• Pregnancy and estrogen therapy increase VWF 3
• Blood type O has 25-60% lower baseline VWF levels 1, 3

Pediatric Considerations

For children with easy bruising, add:

• Serum calcium, phosphorus, and alkaline phosphatase for bone metabolism disorders 1
• Parathyroid hormone and 25-hydroxy-vitamin D 1
• Serum copper and ceruloplasmin 1
• Consider non-hematologic causes including connective tissue disorders, medication effects, and non-accidental trauma 1

Documentation

Use a structured bleeding assessment tool (ISTH-BAT or Pediatric Bleeding Questionnaire) to quantify bleeding severity, as 80% of specialists use these instruments and they influence the extent of testing ordered. 1 This standardized approach ensures you capture relevant bleeding history that guides appropriate test selection.