From George: Long ago at a Temple University-sponsored meeting in Philadelphia, Dr. Dorothy Adcock provided data showing it was unnecessary to collect a "discard" tube ahead of a blue-closure hemostasis specimen.
Conventional wisdom prior to hers and the work of others was that a discard tube was necessary to avoid contamination with "tissue thromboplastin," which could interfere. I naively asked Dr. Adcock, "What about traumatic venipunctures?" to which she responded she'd not been able to consent subjects to agree to a traumatic venipuncture!"
Now we no longer require a discard tube unless collecing through an infusion set (just to offset the volume of air in the set), but we still state that it is necessary to avoid traumatic venipunctures when collecting hemostasis specimens. Yesterday Dave McGlasson asked if I knew of any data that proves a traumatic venipuncture affects coagulation laboratory results, so I told him the story of Dr. Adcock and my question. I've never seen data on this, and presume the requirement is based on pure logic and expert opinion. Does any of our participants have something to add? A reference or data, perhaps? Please comment below.
Reference: McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: is a second tube necessary? Clin Lab Sci.1999;12:137–9.