What is the recommended order of draw for multiple blood tubes?

• A. Sterile cultures (if used), blue (citrate), red/gray (serum), green (heparin), gray (fluoride), purple (EDTA)
• B. Sterile cultures (if used), blue (citrate), red/gray (serum), green (heparin), purple (EDTA), gray (fluoride)
• C. Sterile cultures (if used), blue (citrate), red/gray (serum), purple (EDTA), green (heparin), gray (fluoride)
• D. Sterile cultures (if used), blue (citrate), red/gray (serum), purple (EDTA), gray (fluoride), green (heparin)

Answer: (B)

The order of draw is all about preventing additive carryover from one tube to the next, so test results stay accurate. Start with sterile culture bottles when cultures are being drawn to avoid contaminating specimens. Then collect the light-blue top tube containing sodium citrate first, because citrate can alter coagulation measurements if it’s introduced later. Next come the red or red-gray serum tubes, which allow the blood to clot and provide serum for many tests. After that, draw the green top tube with heparin for plasma chemistry work. Follow with the purple top tube containing EDTA for hematology, since EDTA can interfere with calcium-dependent processes if it contaminates other tubes. Finally, draw the gray top tube with fluoride/oxalate last for glucose testing, minimizing any potential impact on other assays. This sequence matches the option that lists sterile cultures, blue, red/gray, green, purple, and gray. The other sequences place additives out of order (for example, fluoride before EDTA or mixing up green and purple), which can compromise test accuracy.