Blood collection tubes must be drawn in a specific order to avoid cross-contamination of additives between tubes. The recommended order of draw for plastic vacutainer tubes is: First - blood culture bottle or tube. Second - coagulation tube (light blue top). If just a routine coagulation assay is the only test ordered, then a single light blue top tube may be drawn. If there is a concern
. regarding contamination by tissue fluids or thromboplastins, then one may draw a non-additive tube first, and then the light blue top tube. Third - non-additive tube (red top). For more information, visit http://www.phlebotomypages.com/new_draw.htm
