What is the correct order of draw for blood specimens?

The order of draw for blood specimens is important to prevent cross-contamination of additives between tubes and ensure accurate lab results. The correct sequence begins with blood cultures to minimize the risk of contamination since these samples are crucial for identifying infections. After blood cultures, the next is the light blue tube, which contains sodium citrate, an anticoagulant necessary for coagulation studies. Following the light blue tube, the red tube is drawn; this is often a serum tube that can either be a plain red without additives or one with a clot activator. Then, the green tube containing heparin, another type of anticoagulant, is used for various tests that require plasma.

The lavender tube follows, which contains EDTA, an anticoagulant primarily used for hematological tests, such as complete blood counts. Finally, the gray tube is drawn, which typically contains additives to preserve glucose levels or inhibit glycolysis for specific tests.

This order helps to ensure that any additives from later tubes do not interfere with the tests conducted on samples collected earlier. In summary, the rationale for the order of draw is primarily based on the need to avoid contamination and the functional role of each type of tube in blood testing.