Are all coagulation specimens collected into 3.2% buffered sodium citrate?
Note: The milder chelation of 3.2% citrate over 3.8% citrate is preferred for accuracy of results. Sodium citrate is effective as an anticoagulant due to its mild calcium-chelating properties. Of the two commercially available forms of citrate, 3.2% buffered sodium citrate (109 mmol/L of the dihydrate form of trisodium citrate Na3C6H5O7 2H20) is the recommended anticoagulant for coagulation testing. The citrate concentration in 3.8% sodium citrate is higher and its use may result in falsely lengthened clotting times with calcium-dependent coagulation tests (i.e., PT and aPTT) with slightly underfilled samples and with samples with high hematocrits. Coagulation testing cannot be performed in samples collected in EDTA due to the more potent calcium chelation. Heparinized tubes are not appropriate due to the inhibitory effect of heparin on multiple coagulation proteins. If the laboratory does not adhere to recommendations for use of 3.2% buffered sodium citrate, it must have data on file
