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A BAYESIAN APPROACH TO THE DIAGNOSIS OF TYPE 1 VON WILLEBRAND DISEASE
Abstract number: P-T-177
Tosetto1 A., Castaman1 G., Rodeghiero1 F.
1Department of Hematology, San Bortolo Hospital, Vicenza, Italy
How-to-cite Tosetto A, Castaman G, Rodeghiero F. A BAYESIAN APPROACH TO THE DIAGNOSIS OF TYPE 1 VON WILLEBRAND DISEASE. J Thromb Haemost 2007; 5 Supplement 2: P-T-177
Abstract
Introduction: So far, criteria for the diagnosis of type 1 von Willebrand disease (VWD) have been based on consensus among experts rather than on evidence. In this study we present a proposal for combining clinical and laboratory criteria for VWD diagnosis using likelihood ratios obtained from currently available evidence.
Methods: According to the Bayes' theorem, the odds of having a disease could be computed as the product of prevalence of the disease and of the likelihoods ratios of disease given a test result. Assuming a prevalence of VWD of 1/1,000, we estimated the likelihood ratios (LR) of being a type 1 VWD on the basis of the patient bleeding score (BS, a summative index of number and severity bleedings occurred during lifetime), von Willebrand factor (VWF) level, and probability of having one or more first-degree family members with reduced VWF. LR for bleeding score and VWF were computed from published data (Rodeghiero et al, 2005). LR for inheritance was modeled by computer simulation under the hypothesis of an autosomal dominant transmission in nuclear families. We propose that a diagnosis of VWD could be considered as possible when supported by odds from 2 to 10 and definite for odds > 10.
Results: In the absence of other family members with reduced VWF, the diagnosis was possible only for VWF values < 40 IU/dL and BS > 3. The presence of at least another family member with reduced VWF made the diagnosis definite for VWF values < 40 IU/dL and BS > 3. Two or more family members with reduced VWF being present, the diagnosis could be considered as definite, even for mildly reduced VWF (40-60 IU/dL) in the presence of bleeding symptoms.
Conclusions: Demonstration of the inheritance of reduced VWF is required in those patients with mild bleeding symptoms and/or VWF reduction. In the absence of the inheritance criterion, only those patients with a clear-cut bleeding history (BS>5) and VWF < 20 IU/dL could be considered as definite VWD.
To cite this abstract use the following format:
Journal of Thrombosis and Haemostasis 2007; Volume 5, Supplement 2: abstract number
Session Details
| Date: |
01/08/2007
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| Time: |
00:00-00:00
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| Session name: |
XXIst ISTH Congress |
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| Location: |
Oxford, UK |
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