Which tube comes third in the order of draw?

The order of draw is an essential aspect of phlebotomy that helps prevent cross-contamination of additives in blood collection tubes, which can affect test results. In this case, the light blue tube is indeed associated with the third position in the order of draw.

The light blue tube is primarily used for coagulation studies, and its specific additive, sodium citrate, requires a precise blood-to-additive ratio for accurate results. Collecting it in the correct sequence helps maintain the integrity of coagulation tests by ensuring the sample is not contaminated by the residual additives from other tubes.

The standard order of draw generally starts with blood cultures, followed by tubes with additives such as those for serum tests, and then the light blue tube. Therefore, the selection of the light blue tube as the third in the order aligns with established practices in phlebotomy, ensuring that coagulation tests yield reliable outcomes.