Sodium Citrate Blood Collection Tube 1:4 ESR Black Top 3.8% Product Overview Sodium Citrate 1:4 Blood Collection Tube is a black-top ESR tube designed for blood collection in erythrocyte sedimentation rate (ESR) testing . The tube contains 3.8% sodium citrate as an anticoagulant, with a 1:4 anticoagulant-to-blood ratio for the stated testing application. It is commonly used with the traditional Westergren method for measuring erythrocyte sedimentation rate. Available in glass