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The specimen of choice for coagulation testing is plasma. Venous blood is drawn into a 3.2% buffered sodium citrate tube (blue top tube), yielding a whole blood sample with a 9:1 blood to anticoagulant ratio. Inadequate filling of the collection tube will decrease this ratio, and may affect test results. A blue top tube used for coagulation testing should be drawn before any other tubes containing additives. This includes tubes containing other anticoagulants and/or plastic serum tubes containing clot activators. A serum tube that does not contain an additive can be collected before the blue top tube. If a winged blood collection set is used in drawing a specimen for coagulation testing, a discard tube should be drawn first. The discard tube must be used to fill the blood collection tubing dead space to assure that the proper anticoagulant/blood ratio is maintained, but the discard tube does not need to be completely filled. The discard tube should be a nonadditive or a coagulation tube. If a blood specimen used for coagulation testing must be collected from an indwelling line that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood or 6-times the line volume (dead space volume of the catheter) be drawn off and discarded before the coagulation tube is filled.

Some global specimen collection and handling issues to consider include: Specimens that contain nucleated cells will be of interest in DNA methodologies while specimens lacking nucleated cells are more useful in RNA methodologies. rRNA is more stable than mRNA, which is labile and sensitive to contamination. DNA is relatively stable and can be obtained from nonviable sources. Serum or plasma obtained by standard routine venipuncture procedures can be used as long as proper site selection and decontamination occur. Standard anticoagulants such as Ethylenediaminetetraacetic Acid (EDTA) and Acid Citrate Dextrose (ACD) can be used; however avoid the use of heparin as an anticoagulant as it interferes with some polymerase chain reaction (PCR) methodologies. When using fluorescence, fasting serum or whole blood specimens should be used to decrease the interference by lipids.

Contain either acid citrate dextrose (ACD), which maintains RBC viability and may be used for HLA phenotyping, DNA, paternity testing, or lymphocyte surface markers, or: Sodium polyanetholesulfonate (SPS) which is sometimes used to collect blood culture specimens.