PB0826 - Examining plasma Von Willebrand Factor (VWF) thresholds to reduce repeated VWF testing in adults

Monday, June 26, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Bryan Dillon, MB BCh BAO

Senior House Officer, Junior Doctor
St James's Hospital Dublin
Cork, Cork, Ireland

Co-Author(s)

MR

Marie Rafferty

Senior Clinical Scientist
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
SB

Shona Brady

Clinical Nurse Specialist
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
Mairead Doyle, MSc

Medical Scientist
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
AG

Anu George

Nursing Manager
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
MB

Mary Byrne

Coagulation Laboratory Chief
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
KR

Kevin Ryan

Consultant Haematologist
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
NO

Niamh O'Connell, MD

Consultant Haematologist
National Coagulation Centre, St James's Hospital, Dublin
Dublin, Dublin, Ireland
JO

James S. O'Donnell, MB, PhD

Professor of Haematology
Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland,Dublin, Ireland
Dublin, Dublin, Ireland
Michelle Lavin, MB, PhD (she/her/hers)

Consultant Haematologist
National Coagulation Centre, St. James Hospital and Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Physicians and Surgeons in Ireland (RCSI)
Dublin, Dublin, Ireland

Background: Repeated von Willebrand Factor (VWF) testing over time is required in the assessment of von Willebrand Disease (VWD), particularly those with borderline levels. A plasma VWF threshold n adults attending for haemostatic workup above which repeated testing is not required is yet to be defined.

Aims: To systemically review VWF results from a large haemostasis centre to identify VWF levels above which re-testing is not indicated.

Methods: Factor VIII (FVIII:C) and VWF results from St James’s Hospital (December 2020-2022) were reviewed, identifying those with ≥2 VWF levels undergoing haemostatic assessment. Known VWD patients, VWF levels < 0.30IU/mL and pregnant women were excluded.

Results: 2138 samples on 1029 patients were identified. Following exclusion, a total of 454 patients were analysed (median age 38.7years [y], range 16.9-85.1y; 76% female). Of these, 43(9.5%) had 2 consecutive low plasma VWF levels (0.30-0.50IU/mL, “Low/Low”,72% female); 40(8.8%) had one normal, one low level (‘Normal/Low” female 72.5%) and 371(81.7%) had 2 normal plasma VWF levels(“Normal/Normal“, female 76.7%). No significant difference in age was seen between these three groups (median 31.6y vs 35.8y vs 39.4y, all p>0.05, Figure 1A).

FVIII:C levels exhibited variability but were significantly lower in those with at least one low VWF level(Normal/Low median 0.81 IU/mL; Low/Low median 0.73IU/mL) than the Normal/Normal group (median 1.19IU/mL, p< 0.0001 for both, Figure 1B). VWF levels < 0.50IU/mL were found even with FVIII:C levels up to 1.16IU/mL. In the Normal/Low group(n=40) the median VWF:RCo on first test was 0.58IU/mL but a wide range was seen(0.52-0.97IU/mL,Figure 1C), highlighting the need to re-test if clinical suspicion is present. Plasma VWF:RCo≥0.70IU/mL had a 99.3% negative predictive value for VWD.

Conclusion(s): Data from this cohort attending for haemostatic testing suggests a threshold of VWF:RCo≥0.70IU/mL may be used to exclude the need for repeat VWF testing. This offers the opportunity to reduce patient inconvenience and laboratory demand.