What is the fourth tube in the CLSI order of draw?

The fourth tube in the CLSI order of draw is the EDTA tube, which is typically lavender in color. This order is crucial in phlebotomy because it helps prevent contamination of samples that can lead to inaccurate test results.

In the CLSI order of draw, blood collection begins with tubes that contain additives to ensure that coagulation does not occur. The correct sequence starts with a sterile blood culture tube, followed by the citrate tube (usually blue), then the serum tube (red or gold), and finally the EDTA tube (lavender). The use of EDTA is common in hematology because it acts as an anticoagulant, preserving blood cells for complete blood counts (CBC) and other tests, but it is also essential that it is drawn last to prevent any possible contamination from additives in prior tubes.

Understanding the order of draw is vital for ensuring specimen integrity and accurate laboratory results, making the identification of each tube and its purpose essential knowledge for phlebotomy technicians.