What is the initial investigation for a 17-year-old female presenting with easy bruising?

Initial Investigation for Easy Bruising in a 17-Year-Old Female

Begin with a complete blood count (CBC) with platelet count, peripheral blood smear, prothrombin time (PT), and activated partial thromboplastin time (aPTT) as the initial screening panel. 1, 2

History and Clinical Assessment

Before ordering laboratory tests, obtain specific information to determine if testing is warranted:

• Bleeding symptoms: Ask specifically about significant bleeding after surgery, dental procedures, circumcision (if applicable), epistaxis requiring medical attention, menorrhagia, or joint hemorrhages 1, 3
• Family history: Document any known bleeding disorders in relatives, as von Willebrand disease and hemophilia have hereditary patterns 1, 4
• Medication review: All medications including NSAIDs, anticoagulants, antiplatelets, steroids, and alternative therapies must be documented, as these can affect both bleeding tendency and coagulation test results 1, 3
• Bruising pattern: Determine if bruising location correlates with normal activity for age and developmental stage 1

Initial Laboratory Testing

The screening panel evaluates for conditions with prevalence greater than 1 per 500,000:

• CBC with platelet count: Screens for thrombocytopenia and immune thrombocytopenia (ITP) 1, 2
• Peripheral blood smear: Evaluates platelet morphology and identifies hematologic abnormalities 1, 2
• PT and aPTT: Detect most factor deficiencies affecting intrinsic and extrinsic coagulation pathways 1, 2
• Fibrinogen level: Should be added if PT or aPTT are abnormal to detect fibrinogen defects 1, 3

Critical Limitation to Recognize

Normal PT and aPTT do NOT rule out bleeding disorders. These tests miss von Willebrand disease (the most common inherited bleeding disorder with prevalence of 1 in 1000), factor XIII deficiency, and platelet function disorders. 1, 5, 4

Interpretation Algorithm

If PT and aPTT are both normal:

• Consider von Willebrand disease (most likely diagnosis in this demographic) 5, 4
• Consider platelet function disorders 1, 4
• Refer to hematology for von Willebrand testing and possible platelet function studies 1, 2

If PT normal and aPTT prolonged:

• Indicates intrinsic pathway disorder (Factor VIII, IX, XI, or XII deficiency) 2, 4
• Perform mixing study to distinguish factor deficiency from inhibitor 4

If PT prolonged and aPTT normal:

• Indicates extrinsic pathway disorder (Factor VII deficiency) 2, 4
• Consider vitamin K deficiency, though less common in adolescents 4

If both PT and aPTT prolonged:

• Consider liver disease, vitamin K deficiency, or combined factor deficiencies 4
• Evaluate for disseminated intravascular coagulation (DIC) if clinically indicated 1, 5

Additional Considerations for This Population

In a 17-year-old female specifically:

• Menstrual history: Heavy menstrual bleeding is a common presentation of von Willebrand disease in adolescent females 1
• Connective tissue disorders: Examine for signs of Ehlers-Danlos syndrome (joint hypermobility, skin hyperextensibility, atrophic scarring), which can cause easy bruising independent of coagulation abnormalities 1, 6

When to Refer to Hematology

Refer when: 1, 2

• Initial laboratory evaluation indicates a bleeding disorder
• High clinical suspicion persists despite normal screening tests
• Specialized testing (von Willebrand studies, platelet aggregation, factor XIII assay) is needed
• Complex interpretation is required

Common Pitfalls to Avoid

• Do not assume normal screening tests exclude bleeding disorders - they miss the most common inherited bleeding disorder (von Willebrand disease) 1, 5
• Do not perform extensive testing without clinical indication - the extreme rarity of some bleeding disorders makes universal screening unreasonable 3
• Do not overlook medication effects - certain drugs affect both bleeding tendency and test interpretation, particularly platelet function testing 1, 3