Blood collection tubes have become an essential thing in medical tests these days. With the help of these small tubes, healthcare people easily take blood, manage it, and do the test. Through these tubes, the blood sample remains safe and it becomes easy to diagnose diseases. In this blog, we will talk about what these tubes are, what is their use, and what is the right way to use them.
What are Blood Collection Tubes?
Blood collection tubes i.e. vacutainer tubes, these are a type of sterilized tubes that manage the blood sample for testing. These are made of plastic or glass and have some special additives or coating inside which stabilizes the blood. There is a vacuum in them, so the blood flows in a fixed volume in the tube.
Each tube has a different cap color, which tells which additive is in it and for which test it is used. Using the right tube makes the test result accurate.
Types of Blood Collection Tubes (According to Cap Color)
1. Red-Top Tube (empty, without additive)
- Additive: None
- Use: When only serum is needed such as liver function, lipid profile, or antibody test.
- Note: Let the blood clot naturally for 30–60 minutes, then centrifuge.
2. Lavender-Top Tube (EDTA)
- Additive: EDTA — an anticoagulant
- Ideal: Complete Blood Count (CBC), blood group, HbA1c
- Note: Lightly turn the tube upside down 8–10 times to mix.
3. Light Blue-Top Tube (Sodium Citrate)
- Additive: Sodium citrate — prevents clots
- Ideal: PT, aPTT, D-dimer like clotting tests
- Note: The tube must be fully filled or else the ratio will be off.
4. Green-Top Tube (Heparin)
- Additive: Heparin
- Ideal: Electrolyte panel, cardiac test, ABG
- Note: Good for rapid testing, definitely mix 8–10 times.
5. Gold or Tiger-Top Tube (SST)
- Additive: Clot activator and gel separator
- Use: Thyroid, CMP, hormone tests
- Note: Allow 30 minutes for clotting, then centrifuge.
6. Gray-Top Tube (Sodium Fluoride/Potassium Oxalate)
- Additive: to keep glucose stable
- Use: Blood glucose, alcohol level
- Note: Gently invert for 8–10 times.
7. Yellow-Top Tube (SPS or ACD)
- SPS (Sodium Polyanethol Sulfonate): Used for blood cultures.
- ACD (Acid Citrate Dextrose): Used for DNA testing, paternity tests.
- Note: Must be sterile, otherwise contamination may occur.
How do these tubes work?
When the needle is attached to the tube, the vacuum draws out a fixed amount of blood. The additive in the tube either prevents the blood from clotting or causes it to clot – depending on the test requirement.
When the sample is taken, the tube should be gently turned upside down so that the additive and blood are properly mixed. This also prevents hemolysis.
Best Practices: Ways to Use Blood Tubes
Follow the order of draw:
- First Blood Culture (Yellow – SPS)
- Then Coagulation (Light Blue)
- Then Serum (Red/Gold)
- Then Heparin (Green)
- Then EDTA (Lavender)
- Finally Glucose (Gray)
Mix Correctly:
Gently invert each tube as much as suggested.
Filling Correct Volume:
Fill each tube to the mark indicated.
Labeling:
Immediately write the name, ID, date/time on the tube.
Correct Storage:
Store in room temp or fridge as directed.
Do sterile work:
All tools should be clean. There should be no contamination even by mistake.
Common Problems and their Solution
Hemolysis (cell extraction):
Do not shake too vigorously, take the right size needle.
Clotting:
If not mixed, it will clog up – so mix gently.
Wrong Tube:
Test result will be ruined – double check first.
New age tube technology
- Advanced Additives: Now new chemicals keep blood stable for longer.
- Safety Features: The risk of needle stick injury has reduced.
- Small Tubes: Micro-collection tubes for children or those taking less blood.
- Smart Tubes: Tubes with sensors also started coming which monitor the conditions.
FAQs – People’s Questions
A: Every colour means different – it tells what additive is in the tube and for which test it is used.
A: Absolutely not. This is for one time only. If reused, contamination will occur.
A: The result will be wrong, the test will have to be repeated.
A: Every tube is different. For example, CBC (EDTA) is safe for 24 hours at room temperature, but serum tubes need to be centrifuged quickly.
A: The risk is minimal, but a small bruise or infection can occur if the technique is not correct.
Conclusion
Blood collection tubes are like a backbone in today’s diagnostic world. Using them correctly gives accurate test results and the patient’s diagnosis is timely. For those who are in the medical field or are just curious, this guide is a good resource to understand how much responsibility these small tubes entail.
Disclaimer: This blog is meant to share helpful insights and information but is not a substitute for expert medical or laboratory advice. For any specific questions or concerns about blood collection or lab procedures, please consult a qualified healthcare professional or lab specialist.
