The power of a standardized bleeding score in diagnosing paediatric type 1 von Willebrand’s disease and platelet function defects

Authors


  • This work was presented in abstract form at the 51st American Society of Hematology Annual Meeting, New Orleans, LA, December 5th, 2009.

    1PDM and SHO contributed equally to the writing of this manuscript.

Sarah H. O’Brien, MD, MSc, The Research Institute at Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH 43205, USA.
Tel.: +1 614 722 3183; fax: +1 614 722 3544;
e-mail: sarah.obrien@nationwidechildrens.org

Abstract

Summary.  A predictive standardized bleeding questionnaire (Vicenza score), previously validated for identifying individuals with type 1 von Willebrand’s disease (VWD), has never been prospectively validated in tertiary care paediatric settings. The aim of this study was to assess the Vicenza score’s predictive power in identifying type 1 VWD, low von Willebrand factor (VWF) and platelet function defects (PFD) in a prospective cohort of patients, 0–17 years old, referred to a paediatric haematology clinic for evaluation of a bleeding disorder. Before the initial visit, caregivers consented to answer the questionnaire via telephone. Patients’ medical records were reviewed after haematological evaluation. VWF:Ag or VWF:RCo<30 IU dL−1 were labelled ‘definite type 1 VWD’ while 30–50 IU dL−1 were labelled ‘Low VWF’. PFA-100 screening followed by abnormal electron microscopy and/or platelet aggregation studies diagnosed a PFD. At least one haemorrhagic symptom was present in 99 of the 104 children who completed the study (mean number of symptoms 2.87, mean Vicenza score 3.24). Eight met criteria for ‘definite type 1 VWD’, 23 for ‘low VWF’ and 13 for ‘PFD’. The sensitivity, specificity, and positive and negative predictive value (NPV) of the Vicenza score demonstrated poor diagnostic utility with the exception of high specificity in ruling out ‘definite type 1 VWD’. The NPV was comparably high with qualitative (>2 bleeding symptoms) and quantitative (Vicenza score ≥2) criteria. The Vicenza score has limited predictive value in paediatric tertiary care settings. While the NPV of excluding ‘definite type 1 VWD’ is high, simpler qualitative criteria is similarly predictive.

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