Multimer Testing in Patient with VWF:RCo/VWF:Ag Ratio of 0.7
Yes, a VWF multimer test would be helpful for further diagnosis in a patient with a VWF:RCo/VWF:Ag ratio of 0.7, as this borderline ratio suggests a possible qualitative VWF defect that requires multimer analysis to properly classify and manage. 1
Significance of the 0.7 Ratio
A VWF:RCo/VWF:Ag ratio of 0.7 sits precisely at the critical diagnostic threshold that distinguishes between:
- Normal VWF function (ratio >0.7)
- Qualitative VWF defects (ratio <0.7) consistent with type 2 von Willebrand disease (VWD) or acquired von Willebrand syndrome (AVWS) 1
This borderline value creates diagnostic uncertainty that requires further investigation through multimer analysis.
Diagnostic Value of Multimer Testing
Multimer analysis provides crucial information in this scenario:
- Determines the presence or absence of high-molecular-weight (HMW) multimers
- Helps differentiate between VWD subtypes (particularly important for type 2 variants)
- Identifies specific structural abnormalities in the VWF protein 2
- Provides information about increased proteolysis (seen in types 2A and 2B) versus other structural defects 2
Clinical Implications of Multimer Testing
The results of multimer testing directly impact treatment decisions:
- Type 2A vs 2B differentiation is crucial as desmopressin is contraindicated in type 2B VWD (can worsen thrombocytopenia) 1
- Proper classification guides the choice between:
- Desmopressin (may be effective in some type 2 variants but not others)
- VWF concentrate (preferred for most type 2 VWD, especially for surgical procedures) 1
Additional Testing to Consider
In addition to multimer analysis, consider:
- VWF:CB (collagen binding) - provides complementary information about HMW multimers
- RIPA (ristocetin-induced platelet aggregation) - particularly helpful to identify type 2B VWD 2
- VWFpp/VWF:Ag ratio - helps identify variants with increased clearance 3
Risks of Not Performing Multimer Testing
Without multimer analysis in this borderline case (ratio = 0.7), there are significant risks:
- Misdiagnosis of VWD subtype leading to inappropriate treatment choices
- Potential use of desmopressin in type 2B VWD, which could worsen thrombocytopenia and increase bleeding risk 1
- Inadequate prophylaxis for surgical procedures or childbirth
- Missed diagnosis of acquired von Willebrand syndrome
Interpretation of Family History
The fact that both the patient and mother have the same ratio (0.7) suggests:
- Possible hereditary nature of the condition
- Consistent with autosomal dominant inheritance pattern seen in most type 2 VWD variants
- Supports the need for multimer analysis to determine if they share the same qualitative defect
Conclusion
Given the borderline VWF:RCo/VWF:Ag ratio of 0.7 and the presence of this ratio in both patient and mother, multimer testing is essential for proper diagnosis, classification, and management of this potential VWD case. The results will directly impact treatment decisions and help prevent potentially harmful treatment errors.