Final answer:
A light blue tube typically requires a discard tube when it's the first tube to be drawn for accurate coagulation testing, like a VDRL test which detects a flocculant reaction.
Step-by-step explanation:
The light blue tube typically used for blood collection commonly refers to the sodium citrate tube, which is used for coagulation tests. If it is the first tube to be drawn, a discard tube is often needed to ensure that the coagulation tests are accurate. This is because the light blue tube needs to be filled with a precise volume of blood to maintain the correct ratio of sodium citrate to blood, which is crucial for the accuracy of coagulation tests. Drawing a discard tube before the light blue tube helps clear the line of any tissue thromboplastin or air that might contaminate the coagulation sample and lead to inaccurate results. An example of a test performed with the light blue tube is the Venereal Disease Research Laboratory (VDRL) test, which is used to screen for syphilis and involves the detection of a flocculant reaction.