Blue tube use for what blood test?

A blue tube is typically used for coagulation tests, most commonly for prothrombin time (PT) and activated partial thromboplastin time (aPTT). These tests assess the blood's ability to clot and are crucial for monitoring patients on anticoagulant therapy or for diagnosing bleeding disorders. The blue tube usually contains sodium citrate as an anticoagulant, which helps preserve the sample for accurate testing.