When collecting blood samples, it is crucial to follow the correct order of draw to avoid cross-contamination between tubes and ensure accurate test results. The order of draw is based on recommendations from the Clinical and Laboratory Standards Institute (CLSI) and best practices in phlebotomy.
What is order of draw?
Order of draw refers to the sequence in which blood collection tubes should be filled when obtaining multiple samples during a single blood draw. It is designed to prevent cross-contamination between tubes, avoid possible tube additive interference, maintain specimen integrity, and ensure accurate clinical results.
Why is order of draw important?
Following the correct order of draw is important for several reasons:
- Prevents cross-contamination – Blood collection tubes contain additives and preservatives. Drawing tubes in the wrong order can cause cross-contamination between tubes.
- Avoids tube additive interference – Additives like anticoagulants and gel in tubes can interfere with tests if drawn in incorrect order.
- Ensures specimen integrity – Proper order prevents cross-contamination that could affect test results and specimen quality.
- Provides accurate results – Incorrect order can skew test results through cross-contamination and additive interference.
What is the correct order of draw?
The current recommended order of draw according to CLSI guidelines is:
- Blood cultures (If required)
- Sodium citrate tube (blue top)
- Serum tubes with or without clot activators (red or gold tops)
- Heparin tubes (green tops)
- EDTA tubes (lavender tops)
- Glycolytic inhibitor tubes (gray tops)
- Any other tubes
Details on order of draw:
1. Blood cultures
Blood culture bottles should be drawn first if cultures are required. Blood cultures check for bacteria or fungi in the bloodstream that could be causing an infection.
2. Sodium citrate tube
The sodium citrate tube (light blue top) contains sodium citrate anticoagulant. It is used for coagulation testing and should be filled second.
3. Serum tubes
Serum tubes with or without clot activators like silica or polymers should be drawn third. These include red top tubes with no additive or gold top serum separator tubes. They are used for serum testing.
4. Heparin tubes
Green top heparin tubes with lithium or sodium heparin anticoagulants come next. Heparin plasma is used for chemistry tests.
5. EDTA tubes
Lavender top EDTA tubes are filled fifth. EDTA binds calcium to prevent clotting for hematology testing.
6. Glycolytic inhibitor tube
The glycolytic inhibitor tube (gray top) contains fluoride and potassium oxalate. It should be drawn before EDTA if both are required. It inhibits glycolysis to preserve glucose.
7. Any other tubes
Any remaining tube types should be drawn last. This includes specialized tubes like royal blue top trace metal tubes.
Are there any exceptions to the order of draw?
There are a few exceptions when the order may change slightly:
- If only serum tubes and EDTA tubes are needed, the EDTA can be drawn first to avoid contamination from additives in serum tubes.
- For patients with difficult veins, EDTA tubes can be drawn earlier to ensure obtaining blood for hematology testing.
- If a patient is receiving IV fluids that may contaminate blood cultures, other tubes are drawn first before blood cultures.
- With butterflies or syringes, blood culture and sodium citrate tube may be obtained last to avoid anticoagulants contaminating subsequent tubes.
What are consequences of incorrect order of draw?
Drawing tubes in the wrong order can have the following implications:
- Cross-contamination – Additives like anticoagulants can carryover into subsequent tubes, affecting tests.
- Clotted samples – Anticoagulants can cause samples drawn later to clot if tube order is wrong.
- Falsely elevated or decreased results – Carryover between tubes can skew analyte levels higher or lower.
- Unreliable test results – Wrong order affects sample integrity and validity of results.
- Delayed testing and recollections – Erroneous samples may need repeating, delaying treatment.
- Increased costs – Repeat collections lead to added costs of supplies, staff time and processing.
Tips to ensure proper order of draw
Here are some useful tips to maintain proper order of draw during blood collection:
- Label collection tubes in order of draw beforehand.
- Place tubes in correct order within holders before drawing.
- Follow printed order of draw guides available in labs and clinics.
- Use tube charts highlighting the CLSI recommended order.
- Perform slow and steady draws when collecting multiple tubes.
- Use diversion techniques like alternating between tubes during draws.
- Separate and space apart each tube filling.
- Verify order against the printed order after collection.
- Train staff regularly on proper order of draw techniques.
What does order of draw look like in table format?
The order of draw sequence is often depicted visually in tables as well for quick reference. Here is an example table outlining the CLSI recommended order:
| Tube Type | Tube Additive | Tube Color | Tests |
|---|---|---|---|
| Blood culture | Culture medium | Various colors | Microorganism detection |
| Citrate | Sodium citrate | Light blue | Coagulation |
| Serum | Clot activator or none | Red or gold | Serology |
| Heparin | Lithium or sodium heparin | Green | Chemistry |
| EDTA | EDTA | Lavender | Hematology |
| Glycolytic inhibitor | Fluoride, potassium oxalate | Gray | Glucose |
| Other specialty tubes | Various additives | Various colors | Specialized testing |
Conclusion
Following the proper sequence for order of blood draw is a crucial aspect of collecting high quality and reliable blood specimens. Adhering to the CLSI recommended order prevents issues like cross-contamination between tubes, clotting, and inaccurate results. Healthcare workers should have the sequence memorized and utilize visual reminders to ensure the correct order during phlebotomy. Proper technique, training, andtube labeling can help avoid costly errors. Understanding order of draw best practices is key for both healthcare professionals and patients to get the best possible laboratory analysis from blood samples.