Comparison of several von Willebrand factor (VWF) activity assays for monitoring patients undergoing treatment with VWF/FVIII concentrates: improved performance with a new modified automated method. Haemophilia 2015 Nov;21(6):837-45
Date
07/15/2015Pubmed ID
26172561DOI
10.1111/hae.12703Scopus ID
2-s2.0-84946401781 (requires institutional sign-in at Scopus site) 1 CitationAbstract
BACKGROUND: The ability of von Willebrand factor (VWF) to bind platelet GP Ib and promote platelet plug formation is measured in vitro using the ristocetin cofactor (VWF:RCo) assay. Automated assay systems make testing more accessible for diagnosis, but do not necessarily improve sensitivity and accuracy.
OBJECTIVE: We assessed the performance of a modified automated VWF:RCo assay protocol for the Behring Coagulation System (BCS(®) ) compared to other available assay methods.
METHODS: Results from different VWF:RCo assays in a number of specialized commercial and research testing laboratories were compared using plasma samples with varying VWF:RCo activities (0-1.2 IU mL(-1) ). Samples were prepared by mixing VWF concentrate or plasma standard into VWF-depleted plasma. Commercially available lyophilized standard human plasma was also studied. Emphasis was put on the low measuring range. VWF:RCo accuracy was calculated based on the expected values, whereas precision was obtained from repeated measurements.
RESULTS: In the physiological concentration range, most of the automated tests resulted in acceptable accuracy, with varying reproducibility dependent on the method. However, several assays were inaccurate in the low measuring range. Only the modified BCS protocol showed acceptable accuracy over the entire measuring range with improved reproducibility.
CONCLUSIONS: A modified BCS(®) VWF:RCo method can improve sensitivity and thus enhances the measuring range. Furthermore, the modified BCS(®) assay displayed good precision. This study indicates that the specific modifications - namely the combination of increased ristocetin concentration, reduced platelet content, VWF-depleted plasma as on-board diluent and a two-curve calculation mode - reduces the issues seen with current VWF:RCo activity assays.
Author List
Hillarp A, Friedman KD, Adcock-Funk D, Tiefenbacher S, Nichols WL, Chen D, Stadler M, Schwartz BAAuthor
Kenneth D. Friedman MD Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AutomationBlood Chemical Analysis
Factor VIII
Humans
Limit of Detection
Plasma
Platelet Aggregation
Ristocetin
Treatment Outcome
von Willebrand Diseases
von Willebrand Factor
