Blood Collection and Handling
Tube Additives, Tube Type
Most laboratory tests are performed on plasma, serum, or whole blood. To preserve the specimen in the form required by the test, collection tubes contain additives that either prevent coagulation (for plasma and whole blood recovery), or activate coagulation (for serum recovery). Please refer to individual test requirements.
order to prevent a tube additive from contaminating the next tube and altering the chemical composition of the following specimen. Coagulation tests are highly susceptible to interference from contamination from tissue fluid and tube additives; therefore these tests are usually collected first when a series of tubes are collected. Prior to collecting tests for coagulation (i.e. Blue top tube) a plain Clear top tube containing no additive must be partially filled and discarded. This “waste” tube prevents tissue thromboplastins from contaminating the Blue top tube. Blue top tubes must be allowed to fill to the line indicated on the tube, exhausting the vacuum. See Table 1, “Vacutainer Order of Draw” for proper collection order of vacutainer tubes.
Certain blood collection techniques have been identified as possible sources of error in laboratory testing. Avoid the following sources of test error when collecting blood:
Tourniquet left on arm for over a minute before blood collection.
Techniques causing increased trauma to vein or surrounding tissues.
Drawing from a site below an intravenous port.
Drawing from a site that is still wet from the antiseptic used to clean the site.
Inappropriate, expired, or partially filled collection tube.
Drawing multiple tubes out of order.
Patient incorrectly identified.
Tube incorrectly labeled.
Patient preparation instructions were not followed.
Whole Blood, Plasma, and Serum Processing
Draw a sufficient amount of blood with the required anticoagulant to yield the plasma volume required by the test.
Mix. Immediately after collection, gently mix the blood with the tube additive by inverting 8-10 times. Avoid hemolysis of the specimen during collection and mixing.
Place the specimen in a rack at room temperature and centrifuge within 2 hours of collection. Do not refrigerate the sample until the plasma is separated from the cells.
Platelet-Poor Plasma (Double-spun plasma)
Draw a Blue-top tube in the proper tube order. Blue top tubes must be filled to the top of the label mark in order to achieve the proper blood to anticoagulant ratio. Mix well by inverting 8-10 times.
Centrifuge promptly for 15 minutes. Using a plastic pipette, transfer the plasma from the blue top(s) to one or more plastic aliquot tubes, taking care not to disturb the platelet layer that lies on top of the red blood cell layer. Leave a small amount of plasma in the collection tube to be sure you do not pipette out any platelets with the plasma sample.
Cap and centrifuge the transferred plasma sample for another 15 minutes. While the plasma is spinning again, prepare another labeled plastic aliquot tube for the final platelet-poor plasma sample. Indicate “platelet-poor” or “double-spun” plasma on the label.
When the second spin is complete, transfer the top 90% of the plasma from the first aliquot tube into the second aliquot tube, taking care not to disturb any platelets that remain in the bottom of the first tube. Discard this first tube, and promptly freeze the platelet-poor plasma that you have prepared.
Draw a sufficient amount of blood to yield the serum volume required by the test.
Mix. Immediately after collection, mix SST tubes by inverting 8-10 times. This is a very important step! In the past, the glass sides of the collection tubes activated clotting. The switch to plastic tubes due to safety concerns contains a tube additive to activate clotting. For clot formation to occur, tubes must be mixed well. Avoid hemolysis of the specimen during collection and mixing.
Clot. Allow blood to clot by placing in a rack at room temperature for at least 15-30 minutes. Centrifuging specimens before coagulation is complete causes fibrin clots to form in the serum.
Centrifuge within 2 hours of collection. Do not refrigerate the sample until the serum is separated from the cells.
Draw a sufficient amount of blood with the required anticoagulant tube. To achieve an optimum ratio of blood to anticoagulant, the volume of blood should fill the tube to the line indicated on the vacutainer label.
Mix. Immediately after collection, before clotting can occur, gently mix the blood collection tube by inverting 8-10 times.
tore the sample according to the specific test requirements.