title: Measurement of von Willebrand factor activity: relative effects of ABO blood type and race.
abstract: Tests based on three different principles are reported to measure the activity of von Willebrand factor (VWF): ristocetin cofactor (VWF:RCo), collagen binding (VWF:CB), and the so-called "activity ELISA" (VWF:MoAb). We measured these and other diagnostic parameters in a population of 123 randomly selected female study controls, age 18-45 years. Type O subjects had significantly lower levels than non-O subjects in each test. Race differences were seen in all tests except VWF:RCo, with Caucasians having significantly lower levels than African-Americans. ABO differences accounted for 19% of the total variance in VWF:Ag (P < 0.0001) and race for 7% (P < 0.0001), for a total of 26%. Both effects were mediated through VWF:Ag and were independent. VWF:Ag level was the primary determinant of VWF function, accounting for approximately 60% of the variance in VWF:RCo and VWF:CB and 54% of the variance in factor VIII. The ratio VWF:RCo/VWF:Ag differed significantly by race within blood group. The median ratios were 0.97 for type O Caucasians vs. 0.79 for type O African-Americans and 0.94 for non-O Caucasians vs. 0.76 for non-O African-Americans. The ratio VWF:CB/VWF:Ag did not vary. This suggests racial differences in the interaction of VWF with GP1b but not with subendothelium. Alternatively, VWF:RCo may be regulated to maintain a relatively constant plasma level in the presence of excessive VWF:Ag. This heterogeneity within the normal population is partially responsible for the difficulty in defining diagnostic limits for von Willebrand disease.
authors.affiliation: Hematologic Diseases Branch, NCID/DASTLR, Centers for Disease Control and Prevention, 1600 Clifton Road, Mailstop D-02, Atlanta, GA 30333, USA. crm5@cdc.gov
authors.forename: C H
authors.initials: CH
authors.lastname: Miller
authors.forename: E
authors.initials: E
authors.lastname: Haff
authors.forename: S J
authors.initials: SJ
authors.lastname: Platt
authors.forename: P
authors.initials: P
authors.lastname: Rawlins
authors.forename: C D
authors.initials: CD
authors.lastname: Drews
authors.forename: A B
authors.initials: AB
authors.lastname: Dilley
authors.forename: B
authors.initials: B
authors.lastname: Evatt
mesh_terms: D000017:ABO Blood-Group System; D000293:Adolescent; D000328:Adult; D044383:Black People; D001788:Blood Grouping and Crossmatching; D001798:Blood Proteins / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D008875:Middle Aged; D016011:Normal Distribution; D044469:Racial Groups; D012310:Ristocetin / Q000378:metabolism*; D044465:White People; D014842:von Willebrand Diseases / Q000097:blood; D014841:von Willebrand Factor / Q000378:metabolism*; D001741:Black or African American
chemical_list: C048566:A1BG protein, human; D000017:ABO Blood-Group System; D001798:Blood Proteins; D006023:Glycoproteins; D007136:Immunoglobulins; D014841:von Willebrand Factor; D012310:Ristocetin; D003094:Collagen