PB1237 - Validation of a semi-automated Von Willebrand Multimer assay for use in VWD classification

Tuesday, June 27, 2023

18:30 – 19:30 ET

Room: Exhibition

Co-Author(s)

Mairead Doyle, MSc

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

Presenting Author(s)

MB

Mary Byrne

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

Co-Author(s)

BM

Brendan Mullaney

Molecular Biologist
St James Hospital
Dublin, Dublin, Ireland
CK

Cathriona Keenan

Molecular Biologist
St James Hospital
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
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
NO

Niamh O'Connell, MD

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

Background: Von Willebrand Disease (VWD) is sub-classified as Type 1 (quantitative defect), Type 2 (qualitative defect) or Type 3 (absence of Von Willebrand Factor). VWF multimer electrophoresis assesses VWF structural integrity.

Aims: To validate the Sebia Hydragel 5 VWF Multimer Electrophoresis System.

Methods: Parameters evaluated include precision (densitometry), method comparison (versus in-house method), clinical sensitivity (percentage of individuals with a genotype predictive of loss of HMW multimers (Type 2A /2B), clinical specificity (percentage of individuals without a genotype predictive of loss of HMW multimers) and comparison with VWF collagen binding to VWF antigen ratio (ratio indicating qualitative defect < 0.7). Densitometry data was collected for all samples.

Results: Inter-assay precision data was acceptable (n=16) % CV for LMW multimers 12.9%, for IMW multimers 8.7% and for HMW multimers 8.7%. Method comparison (n=16) with the in-house method showed good correlation with 14/16 results in agreement. Clinical sensitivity was 100% (n=8, Type 2A; loss of HMW multimers). Clinical specificity was 100% (n=12, samples without a Type 2A/2B genotype; normal multimer pattern).
A comparison of multimer pattern with VWF:CB/VWF:Ag ratio (n=23) was conducted; an absence of VWF HMW multimers was detected in 9/23 (corresponding ratio < 0.7). HMW multimers were present in the remaining 14/23. The VWF:CB/VWF:Ag ratio was >0.7 in 6/14 and < 0.7 in 8/14 samples. Genotype/phenotype correlation was consistent with multimer results for 5/8 with a borderline ratio (0.6) in 1/8. HMW multimers were present at a lower percentage using densitometry data for the remaining 2/8.

Conclusion(s): The Sebia Hydragel 5 VWF multimer Electrophoresis method was verified for use as a reproducible method sensitive to the presence and absence of HMW multimers. Densitometry data may be useful as an adjunct test in challenging cases. Reliable assessment of the presence of VWF multimers remains an important element of the diagnostic algorithm for the classification of VWD.