What is the appropriate workup for unexplained bruising?

Workup for Unexplained Bruising

Begin with a thorough history and physical examination to determine if laboratory testing is even necessary—many cases with adequate trauma history or clear abuse patterns do not require bleeding disorder workup.

Initial Clinical Assessment

The first critical step is determining whether laboratory evaluation is warranted at all. Laboratory testing for bleeding disorders should be reserved for cases where the clinical picture suggests a possible underlying hemostatic defect 1.

When Laboratory Testing is NOT Needed

Skip the lab workup if any of the following apply 1:

• The trauma history adequately explains the bruising pattern
• The child or independent witness describes abuse or accidental trauma that matches the injuries
• Patterned bruising is present (e.g., hand marks, object imprints)

Key Historical Elements to Assess

Look specifically for these red flags that suggest a bleeding disorder 1:

• Prior bleeding episodes: Excessive bleeding after circumcision, surgery, dental procedures, or from umbilical stump
• Mucocutaneous bleeding: Epistaxis, gum bleeding
• Family history: Known bleeding disorders or ethnic populations with higher prevalence (e.g., Amish)
• Medications: Document all drugs and alternative therapies that may affect hemostasis
• Age and development: Consider whether bruising location matches developmental capabilities

Physical Examination Focus

Examine for 1:

• High-specificity abuse sites: Buttocks, ears, genitals
• Bleeding disorder patterns: Petechiae at pressure points (clothing lines), bruising at infant seat fastener sites
• Other medical conditions: Signs of Ehlers-Danlos syndrome, scurvy, malignancy, arteriovenous malformations

Initial Laboratory Panel

If clinical assessment indicates need for testing, the initial screening panel should include 1, 2, 3:

First-Line Tests

• Complete blood count with platelet count (screens for ITP and thrombocytopenia) 1
• PT (Prothrombin Time) and aPTT (Activated Partial Thromboplastin Time) (detect most factor deficiencies) 1, 2
• Fibrinogen level 1
• Von Willebrand disease testing (VWF antigen, VWF activity, Factor VIII) 1, 4

Important caveat: This initial panel detects conditions with prevalence >1 per 500,000, including ITP, most factor deficiencies (except Factor XIII), and VWD, but does NOT screen for extremely rare conditions 1.

Interpreting Results and Next Steps

Normal PT and aPTT

• Suggests platelet disorder (most commonly von Willebrand disease) 2, 3
• Consider platelet aggregation testing in consultation with hematology 1

Normal PT, Prolonged aPTT

• Indicates intrinsic pathway disorder (e.g., hemophilia A or B, Factor XI deficiency) 2, 3
• Perform mixing study to distinguish factor deficiency from inhibitor 3
• Note: Mild hemophilia may not prolong aPTT but can still cause significant bleeding including intracranial hemorrhage 1

Prolonged PT, Normal aPTT

• Suggests extrinsic pathway disorder (Factor VII deficiency) or vitamin K deficiency 2, 3
• Consider vitamin K challenge 3

Both PT and aPTT Prolonged

• Consider liver disease, disseminated intravascular coagulation, or combined factor deficiencies 3

Special Considerations

Limitations of Standard Testing

Be aware that standard screening misses several important conditions 1:

• Factor XIII deficiency: Not detected by PT/aPTT but can cause severe bleeding
• Mild hemophilia: May have normal aPTT
• Mild platelet disorders: Challenging to detect; PFA-100 has limited utility and many centers have discontinued its use 1
• Fibrinolytic defects: Extremely rare, require specialized testing

Specimen Handling Pitfalls

Coagulation tests are highly sensitive to specimen handling 1:

• False prolongation of aPTT can occur with lupus anticoagulant
• Factor XII deficiency prolongs aPTT but doesn't cause bleeding
• Traumatic brain injury causes transient coagulopathy unrelated to congenital disorders
• Use laboratories experienced with these assays 1

Timing Issues

In children with intracranial hemorrhage who received blood products, delay screening until transfused clotting factors are eliminated 1.

When to Consult Hematology

Refer to pediatric hematology when 1, 4:

• Initial testing suggests a bleeding disorder
• High clinical suspicion persists despite normal initial workup
• Specialized testing needed (platelet aggregation, Factor XIII, fibrinolysis assays)
• Interpretation of complex results required
• Considering genetic testing for bleeding disorder of unknown cause 4

Critical Safety Point

Finding a bleeding disorder does NOT exclude abuse 1. In children with laboratory evidence of a bleeding disorder, follow-up examination after change in home setting can provide valuable information—bleeding disorders are permanent and don't improve with caregiver change (except ITP) 1.