Sunday, January 24, 2010

Meaning of colored caps on blood vials

SST vacutainer spun down, with some serum alre... Image via Wikipedia

If you’ve ever wondered why blood tubes (vacutainers) have different colors, or the reason for the sequence in which they’re taken, take a look at this:


The meaning of the different colors are standardized across manufacturers.

The order of draw refers to the sequence in which these tubes should be filled. The needle which pierces the tubes can carry additives from one tube into the next, and so the sequence is standardized so that any cross-contamination of additives will not affect laboratory results.

Containers containing coagulants
  • Gold or ‘Tiger’ Red/Black top: Clot activator and gel for serum separation
  • Red top PLASTIC tubes: Contains a clot activator and is used when serum is needed
  • Orange or Grey/Yellow ‘Tiger’ Top: Contain Thrombin, a rapid clot activator, for STAT serum testing
Containers containing anticoagulants
  • Green - Contains Sodium Heparin or Lithium Heparin used for plasma determinations
  • Light Green or Green/Gray ‘Tiger’: For plasma determinations in chemistry
  • Purple or lavender – contains EDTA (the potassium salt, or K2EDTA). This is a strong anticoagulant and these tubes are usually used for full blood counts (CBC) and blood films. Lavender top tubes are generally used when whole blood is needed for analysis. Can also be used for some blood bank procedures such as blood type and screen, but other blood bank procedures, such as crossmatches must be in a pink tube in most facilities.
  • Grey – These tubes contain fluoride and oxalate. Fluoride prevents enzymes in the blood from working, so a substrate such as glucose will not be gradually used up during storage. Oxalate is an anticoagulant.
  • Light blue – Contain a measured amount of citrate. Citrate is a reversible anticoagulant, and these tubes are used for coagulation assays. Because the liquid citrate dilutes the blood, it is important the tube is full so the dilution is properly accounted for.
  • Dark Blue – Contains sodium heparin, an anticoagulant. Also can contain EDTA as an additive or have no additive. These tubes are used for trace metal analysis.
  • Pink – Similar to purple tubes (both contain EDTA) these are used for blood banking.
  • Red (glass)- Contains no additives. Tests for antibodies and drugs often require these.
  • Light yellow – Contains sodium polyanethol sulfonate (SPS). Used for blood culture specimens or acid-citrate-dextrose (ACD), used for blood bank studies, HLA phenotyping, and parental testing.
  • Tan (glass or plastic) – Contains either sodium heparin (glass) or K2EDTA (plastic). Used for lead determinations. These tubes are certified to contain no lead.


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