Which of the following tubes is required when drawing blood to measure prothrombin time?

Rationale

Sodium citrate (light blue) is required when drawing blood to measure prothrombin time.

Sodium citrate acts as an anticoagulant by binding calcium ions in the blood, which is essential for the accurate measurement of prothrombin time (PT). This ensures that the blood does not clot before the test is conducted, allowing for reliable results.

A (EDTA (lavender)) YOUR ANSWER

EDTA is an anticoagulant that works by chelating calcium, but it is primarily used in hematology for complete blood counts and other tests that require whole blood. Using EDTA can interfere with coagulation tests, making it unsuitable for measuring prothrombin time.

B (Potassium oxalate (gray)) YOUR ANSWER

Potassium oxalate is another anticoagulant that prevents clotting by binding calcium ions, but it is typically used for glucose testing. It is not appropriate for prothrombin time measurements as it can adversely affect the coagulation process.

C (Sodium citrate (light blue)) CORRECT

Sodium citrate is specifically designed for coagulation tests, including prothrombin time. It maintains the blood sample in a liquid state by chelating calcium, which is crucial for the clotting cascade, allowing for accurate measurement of clotting times.

D (Sodium heparin (green)) YOUR ANSWER

Sodium heparin is an anticoagulant that inhibits thrombin and factor Xa, making it more suitable for certain laboratory tests like chemistry panels rather than coagulation tests. Its use can lead to inaccurate prothrombin time results since it alters the normal coagulation pathway.

Conclusion

In summary, sodium citrate (light blue) is the appropriate choice for drawing blood to measure prothrombin time, as it preserves the sample for accurate coagulation assessment. Other anticoagulants, such as EDTA, potassium oxalate, and sodium heparin, are not suitable due to their interference with coagulation pathways or their intended uses in different types of laboratory testing.

Which of the following tubes is required when drawing blood to measure prothrombin time?

Sodium citrate (light blue) is required when drawing blood to measure prothrombin time.

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