EDTA Blood Collection Tube K2 K3 Purple Top CBC Hematology Testing Product Overview EDTA Blood Collection Tubes are purple-top tubes designed for routine hematology testing and other applications requiring anticoagulated whole blood. Available with EDTA K2 or EDTA K3 , the tubes prevent coagulation by chelating calcium ions in the blood, helping maintain the sample in an anticoagulated state for laboratory analysis. The tubes are suitable for complete blood count (CBC), blood