For a coagulation study, what is the required blood-to-additive ratio in a light blue citrate tube?

For a coagulation study, what is the required blood-to-additive ratio in a light blue citrate tube?

• A. Approximately 9:1 (blood to citrate)
• B. 2:1
• C. 1:1
• D. 4:1

Answer: (A)

In coagulation testing, the amount of anticoagulant must be precisely matched to the blood volume. Light-blue tubes use sodium citrate to chelate calcium, preventing premature clotting while the plasma is prepared. The standard, calibrated ratio is nine parts blood to one part citrate. This 9:1 balance ensures the citrate concentration is correct so calcium binding is exact when the test runs. If the tube is underfilled, too much citrate relative to blood causes excessive calcium chelation and falsely prolonged clotting times; if it’s overfilled, there’s too little citrate and clotting can occur too quickly or results can be unreliable. So the required ratio is approximately 9:1.

In coagulation testing, the amount of anticoagulant must be precisely matched to the blood volume. Light-blue tubes use sodium citrate to chelate calcium, preventing premature clotting while the plasma is prepared. The standard, calibrated ratio is nine parts blood to one part citrate. This 9:1 balance ensures the citrate concentration is correct so calcium binding is exact when the test runs. If the tube is underfilled, too much citrate relative to blood causes excessive calcium chelation and falsely prolonged clotting times; if it’s overfilled, there’s too little citrate and clotting can occur too quickly or results can be unreliable. So the required ratio is approximately 9:1.