Results of our September, 2012 Quick Question:
Historically, what assay was used to monitor heparin?
a. Bleeding time: 14 (17%)
b. Recalcification time: 7 (9%)
c. Lee-White clotting time: 51 (63%)
d. Thromboplastin generation time: 9 (11%)
Participants need to be well-read, or “of a certain age” to answer this one. Bleeding time is incorrect. The Duke, Ivy, or Mielke template BT was used, and may still be used (with little success) to identify vascular disorders, von Willebrand disease, or platelet function disorders. The recalcification time was indeed used to monitor heparin by a few of us. This was a simple test in which calcium was added to citrated (or in those days, oxalated) plasma and the interval to clotting was recorded. The “recal time” grew to be first the partial thromboplastin time, then the present-day activated partial thromboplastin time (PTT, APTT), however, most of us used the Lee-White clotting time. We pipetted fresh, unanticoagulated blood to a 10X75 or 12X75 mm tube, attempted to keep it at 37°C and tipped it every 30 seconds until it clotted, recording the time. The thromboplastin generation time was too cumbersome for routine heparin monitoring, we used it mainly to detect coagulation factor deficiencies.
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