What is the second tube to be drawn according to the order of draw?

The second tube to be drawn according to the order of draw is typically the light blue tube. This tube is used for coagulation studies, such as PT and aPTT, and it contains sodium citrate as an anticoagulant, which is essential for accurate coagulation test results.

When phlebotomists follow the correct order of draw, they help prevent cross-contamination of additives in different tubes, which can alter test results. Following a discard tube, if necessary, prevents any residual anticoagulants from the first tube from contaminating the subsequent sample, but it does not replace the fact that the light blue is standardly drawn second in practice.

The royal blue tube with a red stripe, dark green tube, and discard tube serve specific purposes, but based on standard protocols, the light blue tube is the correct answer.