Which blood collection tube is sensitive to sunlight and should be protected from light for proper coagulation testing?

• A. EDTA
• B. CTAD
• C. Heparin
• D. Sodium citrate

Answer: (B)

Some coagulation testing additives are sensitive to light, so samples must be protected from sunlight to preserve the test results. The CTAD tube uses a citrate-based anticoagulant with added theophylline, adenosine, and dipyridamole to inhibit platelet activation and prevent in vitro changes that can affect platelet-related coagulation measurements. These components are more labile when exposed to light, so protecting the tube from light helps maintain their stabilizing effects and yields accurate coagulation results.

Other common tubes, like those containing EDTA, heparin, or plain sodium citrate, are not primarily distinguished by light sensitivity in routine coagulation testing, so they do not typically require explicit light protection for this purpose.