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3.1.1
Test Tube Order
To prevent contamination, always fill test tubes in this order:
1.
Light blue top: Sodium citrate. Used for coagulation determinations.
2.
Gold top: SST tube with clot activator.
3.
Red top: Serum only, no anticoagulant.
4.
Green top: Lithium heparin. Anticoagulant for chemistry only.
5.
Lavender top: EDTA. Anticoagulant for hematology only.
CAUTION:
Do not remove a sample from the disc and try to reintroduce it to the disc.
Never place green top tubes in a test-tube rocker.
Store samples at room temperature, and use within 60 minutes.
EDTA contamination severely affects results, especially Ca and K+.
Use of a sodium heparin tube will falsely elevate Na+ results.
3.1.2
Venipuncture Using Vacutainer or Syringe
Whole blood samples must be collected using lithium heparin as the anticoagulant. Excess heparin can
interfere with certain chemistries, and can cause dilution. To prevent this, fill the vacutainer tube at
least halfway with sample, then mix well by gently inverting two or three times.
The following venipuncture methods are available:
Preferred method: collecting samples directly into a lithium heparin vacutainer
tube (green top). If additional tubes will be filled, collecting in the following order:
(1) light blue, (2) gold, (3) red, (4) green, (5) lavender. This prevents adverse effects on
results.
Syringe with no anticoagulants. Draw the sample, remove the needle, remove the tube
top, then immediately add the sample to lithium heparin (green top tube). Gently invert
the tube two or three times to mix.
Note:
Do not shake the tube or hemolysis will result.
Testing and Results
3-3
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