The blue top tube is primarily used for which type of test?

The blue top tube is primarily used for coagulation studies, with prothrombin time (PT) being one of the most common tests performed using this tube. This type of test evaluates how long it takes for blood to clot, which is essential for assessing the coagulation pathway and monitoring patients on anticoagulant medications. The specific additive in the blue top tube is sodium citrate, which works by binding calcium in the blood, thereby preventing clotting during the testing process.

Understanding the distinct uses of blood collection tubes is critical for proper sample handling and subsequent test accuracy. Other tests, like the complete blood count and basic metabolic panel, require different tube types to ensure that the additives and properties of the sample are appropriate for the testing methods used.