4 Order of Draw and Tube Selection

Select tubes by test requirements

Correct tube selection and collection technique help preserve specimen quality and support reliable test results. Select tubes according to the test’s stated specimen requirements, not color alone: tube colors and additives can vary by manufacturer. Check the tube label and manufacturer’s information, and follow the laboratory’s current collection manual.

Follow the venous order of draw

When collecting multiple venous specimens during one draw, follow the standard Order of draw to reduce additive carryover:

1. Blood culture bottles or other sterile specimens.

2. Light-blue tubes containing sodium citrate.

3. Serum tubes, plain or with clot activator, with or without gel.

4. Green tubes containing heparin, with or without gel.

5. Lavender or pink tubes containing EDTA, with or without gel.

6. Gray tubes containing a glycolysis inhibitor, commonly sodium fluoride with potassium oxalate.

Some specialized tubes, including yellow ACD and royal-blue trace-element tubes, do not fit neatly into this sequence. Their position depends on the additive and test, so check the laboratory’s instructions. A nonadditive serum tube may be permitted before a citrate tube under certain protocols. A serum tube containing a clot activator should not precede a coagulation tube unless the laboratory specifically directs otherwise.

For a collection involving blood cultures, a coagulation test, a chemistry test, and a CBC, the usual sequence is culture bottles, light blue, serum, then lavender. The order is the same whether blood is collected with an evacuated-tube holder or a syringe. For syringe collections, use an approved safety transfer device.

Recognize common tubes and additives

Tube color is a common guide, not a guarantee of the contents. Verify the exact additive and collection instructions for the tube and test.

• Blood culture bottles: Contain culture medium, with bottle types varying; used for microbiology. Use sterile technique and the facility’s culture protocol.

• Light blue: Contains sodium citrate and is used for coagulation testing, such as PT/INR and aPTT. Fill to the marked volume to maintain the required blood-to-additive ratio; underfilling can distort results.

• Red: May contain no additive or a clot activator, depending on the tube. Used for serum testing. Check the tube specification, allow clotting, and process as directed.

• Gold or tiger-top: Contains clot activator and separator gel and is used for serum chemistry and other tests. Allow the specimen to clot before centrifuging, as specified by the test instructions.

• Green: Contains heparin, sometimes with separator gel, and is used for plasma chemistry and selected tests. Mix gently after collection and use the correct heparin formulation for the test.

• Lavender: Contains EDTA and is used for whole-blood hematology, including CBC. Mix promptly and gently to prevent clots; do not centrifuge unless the test requires it.

• Pink: Contains EDTA and is used for many blood-bank tests. Follow the blood bank’s identification and labeling rules exactly.

• Gray: Commonly contains sodium fluoride with potassium oxalate and is used for glucose and selected tests requiring glycolysis inhibition. Confirm the test-specific tube and handling requirements.

• Yellow or royal blue: Additives vary by tube and purpose, including ACD testing or trace-element testing. Verify the exact additive and collection sequence with the laboratory.

Match specimen type to processing

Specimen type determines how blood is collected and processed.

• Serum: Allow blood to clot, then centrifuge as instructed to separate serum from cells. Do not centrifuge before the required clotting period.

• Plasma: Collect blood into an anticoagulant tube and centrifuge according to the test procedure. The anticoagulant determines which tests are suitable.

• Whole blood: Leave the specimen uncentrifuged for tests that require blood cells, such as many CBCs. Mix additive tubes gently and promptly as directed.

• Citrate specimens: Pay particular attention to fill volume because coagulation testing depends on the correct proportion of blood to citrate. With a winged collection set, air in the tubing can cause the first light-blue tube to be underfilled; follow the laboratory’s procedure for a discard tube when needed.

After collection, invert additive tubes gently the number of times specified by the tube manufacturer or laboratory; do not shake them. Process, centrifuge, separate, store, and transport specimens within the time and conditions specified for the test. These requirements differ among analytes.

Prevent contamination and collection errors

Before collection

Match the request to the required specimen type, tube, volume, and any special preparation or timing instructions. Identify the patient using at least two approved identifiers and compare them with the order. Gather the correct tubes and supplies, and check tube condition and expiration where applicable. Perform hand hygiene and use gloves and standard precautions.

During collection

Clean the site with the appropriate antiseptic and let it dry completely. For blood cultures, follow the specific skin- and bottle-septum-disinfection procedure, and avoid touching the prepared site. Follow the order of draw to limit additive carryover. Use a new sterile collection for each culture site as directed by protocol.

Keep the tourniquet on only as long as needed and follow facility limits; prolonged application can affect some test results. Let evacuated tubes fill to their intended volume. Do not transfer blood forcefully from a syringe or push the syringe plunger into a tube, as this can cause hemolysis and create a needlestick hazard. Use a safety transfer device.

Mix additive tubes gently and promptly. Vigorous shaking can damage blood cells, while failure to mix anticoagulant tubes can allow clots to form. If collection is difficult or a tube is underfilled, do not guess whether it is acceptable; follow laboratory policy or recollect when required.

After collection

Label each tube at the patient’s side immediately after collection, using the required identifiers and collection details. Never prelabel tubes or leave specimens unlabeled for later identification. Check labels against the order and confirm that each specimen is in the correct tube, adequately filled, and properly mixed.

Send specimens promptly under the required transport conditions. Delays, incorrect temperature, the wrong tube, inadequate volume, hemolysis, clotting, or mislabeling may lead to rejection or unreliable results.