Diagnostic Algorithm for Bleeding Disorders
Begin with a structured bleeding history using a validated bleeding assessment tool (ISTH-BAT), followed by targeted laboratory testing based on clinical findings and disorder prevalence, with initial screening tests (CBC, PT, aPTT) followed by specific assays for von Willebrand disease and platelet function disorders when indicated.
Step 1: Clinical Assessment
Bleeding History
Use a standardized bleeding assessment tool to objectively quantify bleeding symptoms 1, 2:
- ISTH-BAT score is most commonly used (73% of experts)
- Normal reference ranges: <3 in children, <6 in adult females, <4 in adult males
- Age-dependent ranges should be considered in adult women
Key bleeding symptoms to assess:
- Mucocutaneous bleeding (epistaxis, gingival bleeding, menorrhagia)
- Easy bruising patterns and locations
- Bleeding after surgery, dental extractions, or trauma
- Gastrointestinal or urinary bleeding
- Hemarthroses or deep tissue hematomas
- Postpartum hemorrhage
Family History
Document bleeding symptoms in first-degree relatives with confirmed diagnostic test abnormalities (98% of clinicians include this) 2.
Physical Examination
Look for specific findings 1:
- Ecchymoses, petechiae, hematomas
- Joint laxity (Ehlers-Danlos syndrome)
- Jaundice or splenomegaly (liver disease)
- Pattern bruising suggesting trauma
Medication Review
Exclude aspirin and NSAIDs that can confound testing 2.
Step 2: Initial Laboratory Screening
Order these tests simultaneously for all patients with suspected bleeding disorder 3:
- Complete blood count (CBC) with platelet count
- Prothrombin time (PT)
- Activated partial thromboplastin time (aPTT)
- Fibrinogen level
Critical caveat: Most factor deficiencies are detected by PT/aPTT, but von Willebrand disease and Factor XIII deficiency are NOT reliably detected by these screening tests 3.
Step 3: Interpretation and Second-Line Testing
If PT/aPTT are Normal but Bleeding History is Significant:
Test for von Willebrand disease (most common inherited bleeding disorder, affects up to 1% of population) 1:
- VWF antigen (VWF:Ag)
- VWF activity (VWF:RCo or VWF:GPIbM)
- Factor VIII level
Diagnostic criteria:
- VWD diagnosed when VWF:Ag and/or activity ≤50 IU/dL
- Repeat testing if VWF levels <80 IU/dL due to diagnostically relevant fluctuations 4
Consider platelet function testing if VWF testing is normal 3:
- Light transmission aggregometry (LTA) with ADP, epinephrine, arachidonic acid, collagen, ristocetin
- Flow cytometric analysis
- Glycoprotein expression analysis
- Note: PFA-100 has limited utility and many centers have discontinued its use due to poor sensitivity for mild disorders 3
If aPTT is Prolonged:
Order specific factor assays 3:
- Factor VIII, IX, XI, XII levels
- Use 50% cutoff for Factor VIII and IX to detect mild hemophilia A or B 4
Important pitfalls 3:
- aPTT can be falsely prolonged with lupus anticoagulant
- Factor XII deficiency prolongs aPTT but does NOT cause bleeding
- Traumatic brain injury causes transient coagulopathy unrelated to congenital disorders
- Specimen handling errors cause false-positives—use experienced laboratories
If PT is Prolonged:
Test Factor VII level and consider liver disease workup.
If Fibrinogen is Low:
- Thrombin time
- Reptilase time
- Consider dysfibrinogenemia
Step 4: Specialized Testing for Rare Disorders
Only pursue if initial testing is normal but bleeding phenotype is severe or family history is compelling 4:
- Factor XIII assay (for delayed bleeding, poor wound healing)
- α2-antiplasmin level (hyperfibrinolysis)
- PAI-1 level (hyperfibrinolysis)
- Thrombomodulin-associated coagulopathy
- Tissue factor pathway inhibitor levels
Step 5: Diagnosis of BDUC (Bleeding Disorder of Unknown Cause)
If all testing is normal but bleeding history remains significant, diagnose BDUC 2, 4. This is a diagnosis of exclusion after ruling out:
- Von Willebrand disease
- Platelet function disorders
- Coagulation factor deficiencies
- Non-hemostatic causes
Special Considerations
Pediatric Patients with Suspected Abuse
Complete history and physical examination are critical before laboratory testing 3:
- Laboratory evaluation is NOT necessary if trauma history adequately explains bruising
- Testing should be based on prevalence, patient/family history, and blood volume requirements
- Delay testing if blood products were transfused until transfused clotting factors are eliminated 3
- Consult pediatric hematologist for complex cases
Timing of Testing
Avoid testing during acute bleeding or immediately after transfusions 3. Factor half-lives vary significantly (Factor VII: 4-6 hours; Factor XIII: 144-300 hours).
When to Consult Hematology
- Abnormal initial screening tests
- Need for specialized platelet function testing
- Suspected rare bleeding disorders
- BDUC diagnosis requiring management guidance 3
The key principle: tailor testing to disorder prevalence and clinical presentation rather than ordering exhaustive panels, as no single panel rules out every bleeding disorder 3.