Category: Quick Question Archive
Our August and September Quick Question, posted Monday, August 27, is mostly for fun, and will appeal most to our more “seasoned” coagulationists. No wrong answer, just some more right than others! Please indicate the assay most often used before the partial thromboplastin time (PTT) for monitoring heparin.
Here is a summary of our July, 2012 Quick Question:
How do you assay for von Willebrand factor (VWF) activity?
a. VWF ristocetin cofactor (VWF:RCo) by aggregometry: 21 (34%)
b. Automated VWF ristocetin cofactor (VWFRCo): 21 (34%)
c. VWF activity immunoassay (VWF:Act): 15 (25%)
d. Collagen binding assay (CBA): 4 (7%)
There’s a definitive article in the June, 2012 JTH that describes the three methods currently available to assay von Willebrand factor activity: ristocetin cofactor (VWF:RCo), collagen binding (VWF:CB), and a monoclonal antibody-based immunoassay (VWF:Act). See Favaloro EJ, Bonar R, Chapman K, Meiring M, Funk (Adcock) D. Differential sensitivity of von Willebrand factor (VWF) ‘activity’ assays to large and small VWF molecular weight forms: a cross-laboratory study comparing ristocetin cofactor, collagen-binding and mAb-based assays. J Thromb Haemost 2012;10: 1043–54. Based on this article, this month’s Quick Question asks which VWF activity assay method you use in your laboratory. Please check out the question at the right and select your answer.
Here’s a summary of our June, 2012 Quick Question:
To perform the chromogenic anti-Xa heparin assay, how many separate reference curves do you maintain for unfractionated (UFH), low molecular weight (LMWH) heparin and fondaparinux?
a. One hybrid curve for UFH and LMWH, same curve (computed) for fonda: 7 (16%)
b. One hybrid curve for UFH and LMWH, a separate curve for fonda: 11 (25%)
c. One reference curve for each heparin: UFH, LMWH, and fonda: 22 (50%)
d. We don’t perform the chromogenic anti-Xa heparin assay: 4 (9%)
Most of us have chosen to stay with three curves rather than take advantage of the various manufacturers’ combined (hybrid) curve that may be used to measure either UFH or LMWH. I’m curious whether those who do not use the hybrid curve find it necessary to confirm the type of heparin being used before running the assay.
Here are the responses to our May, 2012 quick question:
When using point of care testing, at what INR does your anticoagulation clinic require a confirmatory plasma-based (conventional) PT?
a. 4.0: 34 (65%)
b. 5.0: 9 (17%)
c. 6.0: 4 (8%)
d. Never: 5 (10%)
Our responses closely parallel our April 24 and May 7 discussions; it looks like the majority of us prefer caution, knowing the risk of bleeding rises rapidly as the INR exceeds 4.0. Thank you for your participation.