Thromb Haemost 2020; 120(05): 793-804
DOI: 10.1055/s-0040-1709525
Cellular Haemostasis and Platelets
Georg Thieme Verlag KG Stuttgart · New York

Differentiation of Patients with Symptomatic Low von Willebrand Factor from Those with Asymptomatic Low von Willebrand Factor

Eric F. Grabowski
1  Department of Pediatric Hematology/Oncology, Massachusetts General Hospital for Children, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, United States
,
Elizabeth M. Van Cott
2  Department of Pathology, Special Coagulation Laboratory, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, United States
,
Larissa Bornikova
3  Department of Medical Hematology/Oncology, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, United States
,
Daniel C. Boyle
1  Department of Pediatric Hematology/Oncology, Massachusetts General Hospital for Children, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, United States
,
Raisa Lomanto Silva
1  Department of Pediatric Hematology/Oncology, Massachusetts General Hospital for Children, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, United States
› Author Affiliations
Funding This project has been supported by an Investigator-Initiated Grant from CSL Behring and, for equipment maintenance, by the National Institutes of Health (grant No. R01 DK 11 7313).
Further Information

Publication History

22 August 2019

05 March 2020

Publication Date:
05 May 2020 (online)

Abstract

Background Accurate diagnosis of symptomatic low von Willebrand factor (VWF) remains a major challenge in von Willebrand disease (VWD). However, present tests do not adequately take into account flow forces that, at very high shear rates, reveal a weakness in the VWF-platelet glycoprotein glycoprotein Ib bond in normal subjects. The degree of this weakness is greater in symptomatic, but not asymptomatic, low VWF.

Objective The aim of this study is to distinguish patients with symptomatic low VWF (levels in the 30–50 IU/dL range) from those with asymptomatic low VWF and normal subjects.

Methods We measured platelet adhesion (PA)/aggregation in our novel microfluidic flow system that permits real-time assessment of PA (surface coverage) and PA/aggregation (V, aggregate volume) using epifluorescence digital videomicroscopy in flowing noncitrated whole blood at 4,000 second−1. Blood samples from 24 low VWF patients and 15 normal subjects were collected into plastic tubes containing 4 U/mL enoxaparin. MetaMorph software was used to quantify rates of PA and V increase.

Results Rates of PA increase showed a bimodal distribution, with values for 16/24 patients (Group I) all below the 2.5th percentile of normal, and values for 8/24 patients (Group II) similar to controls. Bleeding scores (mean ± standard error) were 5.50 ± 0.45 versus 2.75 ± 0.45 (p = 0.00077), and 10 clinically significant bleeding events were observed in seven versus zero (p = 0.0295) Group I and Group II subjects, respectively.

Conclusion The present approach may offer a definitive means to distinguish symptomatic low VWF from either asymptomatic low VWF or normal controls.

Authors' Contributions

E.F.G. developed the flow system, conceived of the study, performed many of the experiments, wrote the manuscript and enrolled his pediatric patients. L.B. enrolled her adult patients and critically reviewed the manuscript. E.M.V.C. advised on the comparisons with standard VWD assays, revised the discussion text, and critically reviewed the manuscript. R.L.S. collected the information regarding clinically significant bleeding events. D.C.B. assisted with the experiments, digital image analysis, and figures.