Correlation between von Willebrand factor antigen,von Willebrand factor ristocetin cofactor activity and factor VIII activity in plasma |
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Authors: | Giuseppe Lippi Massimo Franchini Gian Luca Salvagno Martina Montagnana Giovanni Poli Gian Cesare Guidi |
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Institution: | (1) Sezione di Chimica Clinica, Dipartimento di Scienze Morfologico-Biomediche, Università di Verona, Ospedale Policlinico G.B. Rossi, Piazzale Scuro, 10, Verona, 37134, Italy;(2) Servizio di Immunoematologia e Trasfusione, Azienda Ospedaliera di Verona, Italy |
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Abstract: | Background The laboratory diagnosis of von Willebrand Factor (VWF) deficiencies includes qualitative and quantitative measurements of
VWF and clotting factor VIII (FVIII). Since the FVIII activity is frequently normal in patients with mild type 1 or 2 von
Willebrand disease (VWD), there is controversy whether FVIII testing should accompany VWF Antigen (VWF:Ag) assay. Methods The aim of this study was to explore the correlation between VWF:Ag, VWF ristocetin cofactor activity (VWF:RCo) and FVIII
in 213 consecutive patients undergoing screening for VWD. Results Forty-six patients were identified with VWF:Ag levels lower than the diagnostic threshold (54 IU/dl). A significant correlation
was observed between VWF:Ag and VWF:RCo (r = 0.892; p < 0.001), VWF:Ag and FVIII (r = 0.834; p < 0.001), VWF:RCo and FVIII (r = 0.758; p < 0.001). Receiver operating characteristic curve analysis of the VWF:Ag assay revealed an area under the curve of 0.978
and 0.957 for detecting life-threatening values of FVIII (<30 IU/dl) and VWF:RCo (<40 IU/dl), respectively. The negative and
positive predictive values at the VWF:Ag threshold value of 54 IU/dl were 100% and 33% for detecting life-threatening FVIII
deficiencies, 94% and 80% for identifying abnormal values of VWF:RCo. Conclusions Due to the excellent correlation between VWF:Ag and FVIII and to the diagnostic efficiency of VWF:Ag for identifying abnormal
FVIII levels in patients with VWF deficiency, routine measurement of FVIII may not be necessary in the initial screening of
patients with suspected VWD. However, the limited negative predictive value of VWF:Ag for identifying type 2 VWD does not
allow to eliminate VWF:RCo or VWF:FVIIIB assays from the diagnostic workout. |
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Keywords: | von Willebrand factor Factor VIII Diagnosis Screening |
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