What lab work is recommended for a patient presenting with bruising everywhere?

Laboratory Workup for Widespread Bruising

For a patient presenting with bruising everywhere, initiate laboratory testing with a complete blood count with platelet count and peripheral smear, PT/INR, aPTT, and fibrinogen level as your first-line panel. 1, 2, 3, 4

Essential First-Line Laboratory Tests

The initial screening panel must include:

• Complete blood count (CBC) with platelet count and peripheral blood smear to identify thrombocytopenia, abnormal platelet morphology, or hematologic malignancies 1, 2, 3, 4

• Prothrombin Time (PT/INR) to evaluate the extrinsic coagulation pathway and detect vitamin K deficiency, liver disease, or factor VII deficiency 1, 2, 3, 4

• Activated Partial Thromboplastin Time (aPTT) to assess the intrinsic coagulation pathway and screen for hemophilia and other factor deficiencies 1, 2, 3, 4

• Fibrinogen level to detect fibrinogen disorders that routine coagulation testing will miss 1, 2, 5

Critical Pitfall: Normal PT/aPTT Does NOT Rule Out Bleeding Disorders

Do not assume normal PT/aPTT excludes all bleeding disorders—these screening tests will miss von Willebrand disease, Factor XIII deficiency, and platelet function disorders. 1, 2, 5, 3

This is the most common diagnostic error in evaluating widespread bruising. Von Willebrand disease is the most common inherited bleeding disorder (prevalence 1 in 1000), yet standard coagulation tests fail to detect it. 5, 3

Additional Testing When Initial Screening is Normal

If PT, aPTT, platelet count, and fibrinogen are normal but clinical suspicion remains high:

• Von Willebrand factor testing panel: VWF antigen (VWF:Ag), VWF ristocetin cofactor activity (VWF:RCo), and Factor VIII coagulant activity to establish or exclude von Willebrand disease 1, 2, 3

• Liver function tests to assess hepatic synthetic function, as liver disease commonly causes coagulopathy 1

• Renal function tests (urea and electrolytes) because uremia affects platelet function 1

Age and Population-Specific Considerations

For Elderly Patients:

• Ferritin and inflammatory markers (ESR or CRP) if concerned about underlying systemic disease or malignancy 1
• Vitamin D and calcium/phosphate if metabolic bone disease may contribute to trauma susceptibility 1
• Medication review is essential—elderly patients frequently take anticoagulants, antiplatelets, NSAIDs, or corticosteroids that increase bruising 1
• Consider senile purpura if bruising is on sun-exposed areas like forearms, which may not require extensive testing if the pattern is typical 1

For Children:

• Serum calcium, phosphorus, alkaline phosphatase to evaluate bone metabolism disorders 2
• Parathyroid hormone and 25-hydroxy-vitamin D for bone metabolism assessment 2
• Serum copper and ceruloplasmin to screen for metabolic disorders 2
• Consider non-accidental trauma in the differential diagnosis, particularly in children under 24 months 6

When to Pursue Specialized Testing

Refer for hematology consultation and specialized testing if:

• Platelet function testing (platelet aggregation studies) when platelet count is normal but clinical suspicion for platelet dysfunction is high 1

• Factor XIII assay if other tests are normal but severe bruising persists, as this deficiency is not detected by standard coagulation tests 1, 5

• VWF multimer analysis if initial VWD testing shows abnormal results or low VWF:RCo to VWF:Ag ratio (below 0.5-0.7) 1, 2

• Mucocutaneous bleeding (nosebleeds, gum bleeding, heavy menstrual bleeding) alongside bruising strongly suggests von Willebrand disease and mandates specific VWF testing 1

Clinical Context Matters

The pattern and distribution of bruising guide the workup:

• Mucocutaneous bleeding suggests platelet dysfunction or von Willebrand disease 3, 4
• Hemarthroses or deep hematomas are more common in coagulopathy (hemophilia) 3
• Patterned bruising in children requires evaluation for abuse 6

Important Timing Consideration

In patients with intracranial hemorrhage who receive blood product transfusions, delay screening for bleeding disorders until elimination of transfused clotting elements. 6 Testing during or immediately after transfusion will yield unreliable results.