Management of Elevated Ristocetin Cofactor with Normal Coagulation Parameters
This patient does not require treatment—the elevated ristocetin cofactor (251% vs upper limit 200%) with normal Factor VIII activity (123%), normal von Willebrand Factor antigen (165%), and normal aPTT (27 sec) represents a benign laboratory finding without clinical significance. 1
Interpretation of Laboratory Results
The key to understanding this case lies in the ratio of VWF:RCo to VWF:Ag, which is critical for determining VWD subtype:
- VWF:RCo/VWF:Ag ratio = 251/165 = 1.52 2
- A ratio above 0.7-1.0 excludes type 2 VWD, which would show ratios below 0.5-0.7 due to qualitative defects 2, 3
- This elevated ratio indicates enhanced VWF function relative to antigen, not a bleeding disorder 1
Why This Patient Does Not Have von Willebrand Disease
Normal or elevated VWF parameters exclude VWD:
- Type 1 VWD requires both VWF:Ag and VWF:RCo to be decreased (typically <50 IU/dL) 1, 4
- Type 2 VWD shows normal or decreased VWF:Ag with disproportionately decreased VWF:RCo (ratio <0.7) 2, 3
- Type 3 VWD presents with severely decreased or absent VWF:Ag (<3 IU/dL) and prolonged aPTT 2
- This patient has none of these patterns 1
Physiologic Causes of Elevated VWF Parameters
Several benign conditions can elevate VWF levels, which should be considered:
- Acute phase reaction: Inflammation, infection, or stress elevates VWF and Factor VIII as acute phase reactants 1, 2
- Pregnancy or estrogen use: Oral contraceptives significantly increase VWF levels 1, 2
- Blood group non-O: Individuals with blood groups A, B, or AB have VWF levels 25% higher than blood group O 1, 2
- Recent exercise or patient stress: Physical activity or anxiety during phlebotomy can transiently elevate VWF 1, 2
Clinical Management Approach
No intervention is required, but documentation is important:
Document the clinical context: Record any acute illness, medications (especially estrogens), recent exercise, or stress during blood draw 1
Assess bleeding history: If the patient has no personal or family history of abnormal bleeding, no further workup is needed 1
Repeat testing only if clinically indicated: If there is a strong bleeding history despite these results, repeat testing under optimal conditions (no stress, fasting, room temperature processing) 1, 2
Do not use these values to guide anticoagulation: Elevated VWF parameters should not influence decisions about thromboprophylaxis or therapeutic anticoagulation 1
Common Pitfalls to Avoid
Critical errors in interpretation:
- Do not confuse elevated VWF:RCo with a bleeding disorder: Elevated values indicate enhanced hemostatic function, not impairment 4, 5
- Do not order VWF multimer analysis: This is unnecessary when VWF:RCo/VWF:Ag ratio is >1.0 and there is no bleeding history 2
- Do not treat with desmopressin or VWF concentrates: These are indicated only for documented VWD with bleeding 4
- Avoid repeat testing without clinical indication: The assay variability (CV 2-8% for automated methods) does not explain a 25% elevation above the reference range 5, 6, 7
When to Consider Further Evaluation
Reassessment is warranted only if:
- The patient develops new abnormal bleeding (mucosal bleeding, excessive bruising, prolonged bleeding after procedures) 1
- There is a family history of bleeding disorders that was not previously documented 1
- Preoperative evaluation reveals bleeding concerns, in which case repeat VWF panel under optimal conditions may be appropriate 2