A Primer on Using Samples for Research

What tube types are best for collecting blood? What should I collect and how for particular end uses? The following information describes samples types and general collection parameters for obtaining materials that will be used for certain research studies.

Whole Blood Collection Tubes

Standard blood collection tubes, called vacutainers, are designed to either have specific antigoagulants to prevent, or in some cases - promote, blood clotting. They also have a slight vaccuum introduced into the container to draw blood into the tube via a venous puncture needle or through a blood catheter line.

Some commonly used vaccutainers have the following "tube top" color and preservatives or anti-coagulants. Also shown in the table below are potential research uses for such samples. More information may be found on Wikipedia's Vacutainer entry or on Becton Dickinson's website

Tube top color Preservative/anti-coagulant Potential Research Uses
Red top None Serum for testing - antibody or complement factor studies, etc. Also useful for electrolytes and other biomarkers, but varies across clinical laboratories whether they routine use serum or plasma for such testing.
Tiger top Serum separator gel Serum for testing, per above. Note, serum separator gel may potentially introduce compounds that could be picked up by mass spec or other highly sensitive studies that broadly survey compounds in fluids.
Gold top Thrombin as a pro-coagulant Serum - used primarily for STAT testing to insure blood rapidly clots. Useful for studies needed serum. As mentioned, added thrombin and clotting factor products may show up in altered amounts if using broad and highly sensitive screening methods.
Green top - light-Kelly Green Lithium heparin as an anti-coagulanti. May have plasma separator gel Plasma - used primarily for detecting blood chemistries and certain biomarkers, such as cardiac enzymes or certain hormones.

Heparinized samples are sub-optimal for DNA extraction as the heparin can interfere with certain components of the extraction kits. The negatively charged heparin may also interfere with other platforms and types of tests.

Green top - dark Green Sodium heparin as an anti-coagulant. May have plasma separator gel. Same considerations as for lithium heparin.
Purple top EDTA as an anti-coagulant. Commonly used for Complete Blood Count (CBC), hemoglobin A1c, and defined testing on red or white cells. Good sample for preparing DNA from blood.
Yellow top Acid citrate dextrose (ACD) as anti-coagulant Used for certain type of coagulation and blood bank testing. Can be used to extract DNA and obtain viable cells for functional studies.
Blue top Sodium citrate as anti-coagulant Used primarily for clotting studies. Sample useful for obtaining DNA.
Grey top Sodium fluoride as an enzyme inhibitor Used for certain glucose, toxicology and other studies where inhibiting continued metabolic activity of RBCs or WBCs is needed.

Not an optimal sample type for DNA or most research biomarker studies. Useful primarily if enzymatic inhibition in the sample is required at the time of draw.