To avoid test error due to additive carryover, a defined order of draw should be followed for both glass and plastic collection tubes when drawing multiple specimens for clinical laboratory testing during a single venipuncture.
All additive tubes should be filled to their stated volumes. As most tubes contain an additive or clot activator that needs to be mixed with the blood sample, tubes must be mixed immediately after drawing. Tubes with anticoagulants (i.e., EDTA) must be mixed immediately to ensure that the specimen does not clot.
After verifying that the collection tubes have not exceeded expiration dates, the following order of draw should be used:
- Blood culture tube/bottle
- Coagulation tube (light-blue top)
- Serum tube with/without clot activator, with/without gel separator (red top, SST gold top, royal blue top with red-striped tube label)
- Heparin tube with/without gel plasma separator (green top)
- EDTA tube with/without gel separator (lavender top, pearl top, royal blue top with purple-striped tube label)
- Oxalate/fluoride tube (gray top)
- Any remaining additive tube (ACD tubes, SPS tubes, etc.)
Note: Waste tubes are required to be collected and discarded before any coagulation test (other than PTI/PTTB) can be collected. The discard tube must be non-additive or another coagulation tube (plastic red tops cannot be used as waste tubes).
When using a winged blood collection set for any coagulation test, the discard tube must be used to prime the tubing of the collection set to assure maintenance of the proper anticoagulant-to-blood ratio in the tube to be drawn for coagulation testing.
If the tube contains an additive, clot activator, or anticoagulant, mix it immediately after it is drawn by gently inverting it 8 to 10 times (holding the tube upright, gently invert it 180 degrees and back to complete one inversion), and then collect the next tube if drawing multiple specimens.