A rapid assay for ristocetin cofactor activity using an automated coagulometer (ACL 9000).
We have set up a rapid assay for measuring the activity of the von Willebrand factor ristocetin cofactor (VWF : RCo) using an automated coagulometer (ACL 9000; Instrumentation Laboratory, Lexington, Massachusetts, USA) and commercially available lyophilized platelet reagents (Dade-Behring, Marburg, Germany). Since VWF : RCo tested with the coagulometer (ACL-VWF : RCo) did not require loading, calculation of von Willebrand factor (VWF) activity or pretreatment of samples (calibration standard and tested plasmas), we thought it might be useful for rapid, automatic screening of VWF activity. To assess the precision and the potency of this ACL-VWF : RCo, we tested the assay in this laboratory's internal normal and abnormal controls, in a group of 67 healthy individuals and in 28 patients with different types of von Willebrand disease (VWD). We compared the ACL-VWF : RCo findings with those of the standard agglutination test (Agg-VWF : RCo), normalizing both assays against VWF antigen (VWF : Ag) measured by 'automatic' and standard enzyme-linked immunosorbent assay 'in-house' methods, to calculate the VWF : RCo/VWF Ag ratios. The within-assay and between-assay repeatability of the automatic ACL-VWF : RCo gave coefficients of variation < 5%, and reproducibility in normal and abnormal laboratory controls gave coefficients of variation of 7.9 and 9.3%, respectively. In VWD patients the results were equivalent to those of the standard Agg-VWF : RCo assay but, because of the good sensitivity, the ACL-VWF : RCo was more accurate in evaluating the VWF : RCo and establishing the VWF : RCo/VWF : Ag ratios in VWD patients with low VWF levels. Moreover, this ACL-VWF : RCo is faster than Agg-VWF : RCo, providing results of calibration curves and of 10 patient samples within 15 min. We can conclude that this automatic ACL-VWF : RCo gives a reliable and useful measure of VWF activity and can be proposed as a screening test for rapid diagnosis of VWD even in patients with low VWF levels in plasma.
Lattuada
Antonella
A
Immunohematology and Blood Transfusion Service, 'L. Sacco' Hospital, Milan
Preda
Luigi
L
Sacchi
Elisabetta
E
Gallo
Luciana
L
Federici
Augusto B
AB
Rossi
Edoardo
E
D000941:Antigens / Q000032:analysis; D001331:Automation; D001780:Blood Coagulation Tests / Q000295:instrumentation*; D002138:Calibration; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008403:Mass Screening / Q000379:methods; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D015203:Reproducibility of Results; D013997:Time Factors; D014842:von Willebrand Diseases / Q000097:blood / Q000175:diagnosis; D014841:von Willebrand Factor / Q000032:analysis* / Q000378:metabolism
D000941:Antigens; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; C029417:Von Willebrand antigen; C094990:adhesion receptor; D014841:von Willebrand Factor; C028254:von Willebrand factor receptor