From Michelle Fahs, MT (ASCP), Clinical Laboratory Educator, Mercy Hospital St. Louis School of CLS.
George, Do you have any recommendations on how the sample should be collected for coag testing if the patient’s hematocrit is >55%? We have in our policy the formula and procedure for adjusting the amount of anticoagulant in the tube to obtain the 9:1 ratio of blood to anticoagulant, but once we break the vacuum seal on the vacutainer tube to adjust the anticoagulant volume it cannot be filled without using a syringe. Since the risk of the sample clotting or hemolyzing is greater when using a syringe to draw the blood, we don’t recommend that either. Any suggestions? Thanks for your help.
Hi, Michelle, I was in Bangor, Maine conducting a seminar today and I tried your question on the audience. They only know of one way to accomplish this, which is to use a syringe, as you suggest. I knew of one lab scientist many years ago who claimed to be able to remove the precise volume without breaking the vacuum by withdrawing a tiny amount of citrate using a tuberculin syringe, but I never actually saw her do it. You can minimize potential clotting by transferring immediately after collection, and gentle withdrawal usually prevents hemolysis. Of course, you must use a safety needle that can be removed without risk of injury prior to transfer.