You are having difficulty drawing blood from a patient and try two successive light blue top, citrate tubes for the collection of a Protime test. Both tubes fill only half full. To avoid redrawing the patient, you pour one tube into the other to make a full tube and send it to the lab. How will this affect the test results?

The results will be affected because the anticoagulant from the two tubes has been combined, doubling it. Pouring two half-full tubes together will change the needed 1:9 ratio of anticoagulant to blood. This will lengthen the time for the Protime and give inaccurate results to the physician.