What initial laboratory studies should be obtained for a patient with new‑onset bruising to evaluate hematologic and hepatic causes of bleeding?

Laboratory Workup for New-Onset Bruising

For a patient presenting with new-onset bruising, order a complete blood count with platelet count and peripheral smear, PT/INR, aPTT, and fibrinogen as your initial panel, and if the bleeding history is strong or mucocutaneous symptoms are present, add the von Willebrand disease triad (VWF:Ag, VWF:RCo, and Factor VIII activity) to this first-line workup. 1, 2

First-Line Laboratory Panel

Essential Hemostasis Tests

• Complete blood count (CBC) with platelet count and peripheral blood smear is performed by 100% of hematology specialists to detect thrombocytopenia, abnormal platelet morphology, and other hematologic abnormalities that may explain bruising 3, 1, 4
• Prothrombin time (PT/INR) evaluates the extrinsic coagulation pathway and can identify factor VII deficiency or liver disease 1, 5, 4
• Activated partial thromboplastin time (aPTT) assesses the intrinsic pathway and detects deficiencies in factors VIII, IX, XI, or XII 1, 5, 4
• Fibrinogen level (Clauss method) screens for fibrinogen disorders and disseminated intravascular coagulation 1, 5

Von Willebrand Disease Screening (Add When Bleeding History Is Strong)

• VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), and Factor VIII coagulant activity should be included in 84% of bleeding evaluations, particularly when mucocutaneous bleeding (easy bruising, epistaxis, menorrhagia) is present 1, 2, 5
• These three tests together establish VWD diagnosis, type, and severity, and are grade B recommendations from the NHLBI 3, 2
• ABO blood group typing is essential because blood type O individuals have 25-30% lower VWF levels than type AB, affecting interpretation 1, 5

Additional First-Line Tests

• Iron studies (ferritin, serum iron, total iron-binding capacity) identify chronic blood loss that may be both cause and consequence of bruising 1, 5
• Liver function tests should be obtained if physical examination reveals jaundice, splenomegaly, or other signs of liver disease 3
• Renal function (BUN, creatinine) is important in elderly patients, as renal insufficiency impairs platelet function 1, 5

Clinical Context That Guides Testing

History Elements to Document

• Medication review must identify all anticoagulants (warfarin, heparin, DOACs), antiplatelet agents (aspirin, clopidogrel), NSAIDs, and supplements, as these alter coagulation pathways 1, 4, 6
• Personal bleeding history including epistaxis >30 minutes, heavy menstrual bleeding, postoperative bleeding, dental procedure bleeding, and prior transfusions 3, 1, 2
• Family history of bleeding disorders is obtained by 98% of specialists and markedly increases pre-test probability of inherited conditions 1, 6

Physical Examination Findings

• Look for ecchymoses, hematomas, petechiae as evidence of active bleeding disorder 3
• Assess for signs of liver disease (jaundice, splenomegaly), joint and skin laxity (Ehlers-Danlos syndrome), telangiectasia (hereditary hemorrhagic telangiectasia), or syndromic features that suggest connective tissue disorders 3, 1, 7
• In vulnerable populations (children, elderly), consider non-accidental trauma 1, 4

Pre-Analytical Considerations for VWD Testing

Timing and patient conditions critically affect VWF levels:

• Avoid testing during acute illness, pregnancy, systemic inflammation, or within 48 hours of strenuous exercise, as these falsely elevate VWF by 25-50% 2, 5
• Minimize patient stress during venipuncture, as anxiety and crying in children or adults elevate VWF and Factor VIII 3, 2
• Oral contraceptives and estrogen therapy increase VWF levels and must be documented 3, 2, 5
• Sample handling: Transport at room temperature, separate plasma promptly at room temperature, and freeze at ≤-40°C if analysis is delayed beyond 2 hours 3, 2, 5

Interpretation Algorithm

When PT and aPTT Are Both Normal

• This pattern suggests a platelet disorder, most commonly von Willebrand disease 4, 6
• Proceed to VWD testing if not already ordered 4, 6

When Only aPTT Is Prolonged

• Indicates a deficit in the intrinsic pathway (factors VIII, IX, XI, XII) 4, 6
• Perform a mixing study to distinguish factor deficiency from inhibitor 3, 4

When Only PT Is Prolonged

• Suggests vitamin K deficiency, factor VII deficiency, or early liver disease 8, 4
• Consider a vitamin K challenge 6

When Both PT and aPTT Are Prolonged

• Evaluate for liver failure, disseminated intravascular coagulation, or combined factor deficiencies 8, 4, 6

VWD-Specific Interpretation

• VWF:RCo <30 IU/dL → definitive VWD diagnosis 5
• VWF:RCo 30-50 IU/dL with compatible history → probable VWD; refer to hematology 5
• VWF:RCo/VWF:Ag ratio <0.5-0.7 → suggests Type 2 (qualitative) VWD; requires VWF multimer analysis 3, 2, 5

Second-Line Testing (When First-Line Is Normal but Bruising Persists)

Coagulation Factor Assays

• Intrinsic pathway factors (FVIII, FIX, FXI) if aPTT is normal but bleeding continues 1, 5
• Extrinsic pathway factors (FII, FV, FVII, FX) when PT/INR is normal but bleeding remains unexplained 1, 5
• Factor XIII activity is frequently overlooked but causes delayed bleeding despite normal PT and aPTT 1, 5

Platelet Function Testing

• Light transmission aggregometry with multiple agonists (ADP, collagen, epinephrine, ristocetin, arachidonic acid) is the gold standard for detecting inherited platelet function defects 1, 5
• Platelet flow cytometry evaluates surface glycoproteins and activation markers 1
• PFA-100/200 may be used as a screening tool, but conflicting data on sensitivity and specificity limit its routine use 1, 2

Specialized VWD Testing

• VWF multimer analysis should be performed only when the VWF:RCo/VWF:Ag ratio is <0.5-0.7 or initial VWD testing shows abnormal results; it is not for initial screening 3, 1, 2, 5

Common Pitfalls to Avoid

• Do not rely on a single laboratory test; no single assay screens for all bleeding disorders 1, 5
• Do not order VWF multimer analysis as part of initial screening; reserve it for reflex testing after abnormal initial results 1, 2, 5
• Do not use bleeding time or PFA-100 for routine screening due to limited sensitivity and specificity 1, 2, 5
• Do not forget to discontinue aspirin and NSAIDs for 7-10 days before platelet function testing to avoid pharmacologic interference 1
• Do not overlook connective tissue disorders (Ehlers-Danlos syndrome) where hematological studies are typically normal except for the Hess test indicating capillary fragility 7

Indications for Hematology Referral

Refer to a hematology specialist when:

• Abnormal initial VWD assay results require subtyping 1, 2, 5
• Strong bleeding history with repeatedly normal laboratory studies, suggesting bleeding disorder of unknown cause (BDUC) 1
• VWF:RCo values 30-50 IU/dL with supportive clinical or family evidence 5
• Initial evaluation indicates a bleeding disorder or suspicion remains high despite normal workup 4, 6