BD Vacutainer® sodium citrate tubes FAQ

Answers to popular questions about BD Vacutainer® sodium citrate blood collection tubes.

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What is the minimum volume of blood that should be collected into a BD Vacutainer sodium citrate tube?

BD tubes are designed to yield within ± 10% of the stated draw volume on the label of the additive tube throughout the entire shelf life. (CLSI guideline - Evacuated Tubes and Additives for Blood Specimen Collection-Fifth Edition H1-A5, 2003)

What are the recommended centrifuge speed and time for the sodium citrate tubes?

CLSI recommends that sodium citrate tubes be spun at 1500 RCF for 15 minutes to achieve platelet poor plasma (platelet count < 10, 000) and accurate coagulation test results.

What do the lines mean on BD Vacutainer Plus sodium citrate tubes?

The etched fill indicator on the plastic citrate tubes indicates the minimum acceptable blood volume in the tube.

With such low draw volume Plus Plastic citrate tubes, will we have enough volume of plasma for testing?

The following bullet points demonstrate that there is enough plasma to perform coagulation testing in a patient with an average hematocrit of 45%.

Tests in a 1.8 mL Plastic Citrate Tube Assuming a Patient Hematocrit of 45:

  • Total plastic citrate tube blood volume is 2.0 mL
  • Packed Cell Volume (PCV) = 2.0 mL x 0.45 = 0.9 mL
  • Subtract PCV from whole blood volume to get volume of available plasma (2.0 - 0.9 = 1.1 mL)
  • Allow 0.4 mL plasma to remain to avoid disturbing the buffy coat (1.1 - 0.4 = 0.7 mL)
  • This still leaves 0.7 mL of plasma available for testing
  • Automated instruments require an average of 100 µl per test for PT and APTT tests, 50 µl for Fibrinogen, and 20 µl for Factor Assays
  • This volume, 0.27 mL, allows for a repeat test, if needed

For 2.7 mL Plus Citrate Tube Assuming a Hct of 45:

  • Total plastic citrate tube blood volume is 3.0 mL
  • PCV = 3 mL x 0.45 = 1.35 mL
  • Subtract PCV from whole blood volume to get volume of available plasma (3.0 - 1.35 = 1.65 mL)
  • Allow 0.4 mL plasma to avoid disturbing the buffy coat cells (1.65 - 0.4 = 1.25 mL)
  • This leaves 1.25 mL of plasma available for testing
  • Automated instruments require an average of 100 µl per test for PT and APTT, 50 µl for Fibrinogen, and 20 µl for Factor Assays (i.e., PT, APTT, Fibrinogen Plus 2 assays = 0.29 mL)

Is a discard tube needed if the only tube being collected is a coagulation tube?

There have been recent articles indicating that drawing a discard tube is not necessary before drawing the sodium citrate tube. In the CLSI coagulation document (H21-A5) it is still recommended that the citrate tube is the second or third tube drawn. However, in the CLSI guideline for Venipuncture Collection (H3-A6) it states that for routine PT and APTT, the first tube drawn may be used for testing.

It is also important to ensure a discard tube is drawn when a blood collection set is used and only a citrate tube is ordered, as the tubing may contain up to 0.5 mL of air that will be drawn into the tube and displace blood volume.

How can the 1.8 mL and 2.7 mL Vacutainer Plus coagulation tubes be differentiated?

The 1.8 mL tube has a light blue rubber stopper covered with a translucent shield and the 2.7 mL tube has a light blue rubber stopper covered with a solid light blue Hemogard™ closure.

What is the blood to additive ratio in the sodium citrate tubes?

The blood to additive ratio is 9 parts blood to 1 part sodium citrate.

What is the additive volume in the BD Plus sodium citrate tubes?

The 1.8 mL draw Plus sodium citrate tube contains 0.2mL of sodium citrate, and the 2.7 mL draw contains 0.3 mL of sodium citrate.

What is the effect of hemolysis on coagulation results?

Hemolyzed specimens should not be processed since there could be activation of the clotting factors. Lipemic or icteric specimens may also interfere with the instrumentation's optical system affecting the coagulation specimen result.

What constitutes a tube inversion?

An inversion is one complete turn of the wrist, 180 degrees, and back. BD recommends that citrate tubes be inverted 3 to 4 times.

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