TECHNICAL NOTESDifferential effect of the ABO blood group on von Willebrand factor collagen binding activity and ristocetin cofactor assayChng, Wee Ja; Yip, Christina YCb; Baliwag, Marilyn Bb; Liu, Te-ChihbAuthor Information aDepartment of Haematology/Oncology and bDepartment of Laboratory Medicine, National University Hospital, Singapore. Sponsorship: This work was funded by the National Medical Research Council (Singapore) grant number R2003/009. Correspondence and requests for reprints to Wee J. Chng, MRCP, Department of Haematology/Oncology, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074, Singapore. Tel: +65 67724971; fax: +65 67775545; e-mail: email@example.com Received 28 May 2004 Revised 10 October 2004 Accepted 11 October 2004 Blood Coagulation & Fibrinolysis: January 2005 - Volume 16 - Issue 1 - p 75-78 Buy Abstract Diagnosis of von Willebrand disease requires a combination of quantitative and qualitative tests including the von Willebrand factor ristocetin cofactor assay (vWF:RCo), the von Willebrand factor collagen binding assay (vWF:CB) and von Willebrand factor antigen quantification (vWF:Ag). Genetic factors, especially the ABO blood group, contribute significantly to the variation in vWF levels and function. Recent studies suggest that ethnicity may be another important modulator. We investigated the effect of the ABO blood group on these tests in 52 blood group O and 54 non-group O Chinese blood donors who were well-matched for sex and age distribution. Group O donors had significantly lower vWF:RCo, vWF:Ag and vWF:CB (P< 0.0001). Reduction in vWF:CB was greater than vWF:RCo in group O donors (53 versus 27%). This led to a lower vWF:CB/vWF:Ag ratio (P< 0.0001) in group O donors whereas the vWF:RCo/vWF:Ag ratio was unaffected (P = 0.97). These variations should be taken into consideration when interpreting these results in the Chinese. © 2005 Lippincott Williams & Wilkins, Inc.