What laboratory tests should be obtained for an adult presenting with easy bruising?

Laboratory Workup for Easy Bruising in Adults

Order a complete blood count with platelet count and peripheral smear, PT/INR, aPTT, and fibrinogen as your initial panel, then add von Willebrand factor testing (VWF:Ag, VWF:RCo, and Factor VIII) if the patient has mucocutaneous bleeding symptoms or a suggestive bleeding history. 1, 2

First-Line Laboratory Tests

The initial workup should include:

• Complete blood count (CBC) with platelet count and peripheral blood smear to identify thrombocytopenia, abnormal platelet morphology, or other hematologic abnormalities 3, 1, 2
• Prothrombin time (PT/INR) to assess the extrinsic coagulation pathway 1, 2
• Activated partial thromboplastin time (aPTT) to evaluate the intrinsic coagulation pathway 1, 2
• Fibrinogen level to screen for fibrinogen disorders 1, 2

Critical caveat: PT and aPTT alone will miss von Willebrand disease and mild platelet function disorders, which are among the most common causes of easy bruising 1. Do not rely solely on these screening tests to rule out bleeding disorders.

Von Willebrand Disease Testing

Add VWD testing to your initial panel if the patient reports:

• Easy bruising with mucocutaneous bleeding (nosebleeds, heavy menstrual bleeding, gum bleeding) 3
• Personal or family history of bleeding with surgery, dental procedures, or childbirth 3, 4
• Bleeding symptoms despite normal PT/aPTT 1

The three mandatory VWD assays are:

• Von Willebrand factor antigen (VWF:Ag) – measures quantity of VWF protein 1, 4
• Von Willebrand factor ristocetin cofactor activity (VWF:RCo) – measures VWF function 1, 4
• Factor VIII coagulant activity – often reduced in VWD 1, 4

Order all three tests simultaneously because 84% of bleeding evaluations include this panel, and it establishes both diagnosis and severity 2. Normal reference ranges are 50-200 IU/dL for all three tests 4.

Additional First-Line Considerations

• ABO blood type – Type O individuals have 25-30% lower VWF levels than type AB, affecting interpretation 2, 4
• Medication review – Document all anticoagulants, antiplatelet agents (aspirin, NSAIDs, clopidogrel), and supplements 2
• Iron studies (ferritin, serum iron, TIBC) – to identify chronic blood loss 2

Pre-Analytical Requirements for Accurate Testing

Avoid testing during:

• Acute illness, pregnancy, or systemic inflammation (falsely elevates VWF) 4
• Within 48 hours of strenuous exercise 4
• During significant patient stress or anxiety 4

Sample handling: Blood for VWF assays must be transported at room temperature, plasma separated promptly, and frozen at ≤-40°C if testing is delayed beyond 2 hours 4.

Interpretation Algorithm

If PT and aPTT are both normal:

• Consider platelet function disorder or mild von Willebrand disease 5
• Proceed to VWD testing if not already done 1
• Consider second-line platelet function testing if bleeding history is convincing 2

If aPTT is prolonged but PT is normal:

• Suggests intrinsic pathway defect (factors VIII, IX, XI) 5, 6
• Check VWD panel if not done – mild VWD commonly presents this way 6
• Consider factor VIII, IX, and XI assays 2

If PT is prolonged but aPTT is normal:

• Suggests extrinsic pathway defect (factor VII) 5
• Consider factors II, V, VII, X assays 2

If VWF:RCo/VWF:Ag ratio is <0.5-0.7:

• Indicates Type 2 (qualitative) VWD rather than Type 1 1, 4
• Requires VWF multimer analysis for subtyping 1, 4

If VWF:RCo is 30-50 IU/dL with supportive clinical/family history:

• Likely VWD – repeat testing and consider hematology referral 4

Second-Line Testing (When First-Line Tests Are Normal but Bleeding Persists)

• Intrinsic pathway factors (FVIII, FIX, FXI assays) 2
• Extrinsic pathway factors (FII, FV, FVII, FX assays) 2
• Factor XIII activity – frequently overlooked but causes delayed bleeding despite normal PT/aPTT 2
• Light transmission aggregometry with multiple agonists (ADP, collagen, epinephrine, ristocetin, arachidonic acid) – gold standard for platelet function defects 2
• Platelet flow cytometry to evaluate surface glycoproteins 2

Important: Discontinue aspirin and NSAIDs for 7-10 days before platelet function testing to avoid false results 2.

When to Refer to Hematology

Immediate referral is indicated for:

• Abnormal VWD assay results requiring subtyping 4
• Strong bleeding history with repeatedly normal laboratory tests 4
• VWF:RCo 30-50 IU/dL with clinical/family history 4
• Suspected acquired von Willebrand syndrome (associated with aortic stenosis, lymphoproliferative disorders, monoclonal gammopathies) 4
• Need for specialized assays (multimer analysis, genetic testing) 4

Common Pitfalls to Avoid

• Do not order VWF multimer analysis as an initial test – it is complex, costly, and should only follow abnormal initial VWD results 4
• Do not use bleeding time or PFA-100 as screening tools – they have inconsistent sensitivity and specificity for VWD 4
• Do not overlook non-hematologic causes – consider connective tissue disorders, medication effects, and in vulnerable populations, non-accidental trauma 1
• Do not forget to assess renal function – renal insufficiency impairs platelet activity and contributes to bleeding 2

Special Pediatric Considerations

For children with easy bruising, also consider:

• Bone metabolism screening: serum calcium, phosphorus, alkaline phosphatase 1
• Parathyroid hormone and 25-hydroxy-vitamin D 1
• Serum copper and ceruloplasmin 1
• Bone marrow examination is NOT necessary in children with typical ITP features 3