Understanding which color blood bottle to use is crucial for accurate diagnostic testing, as each color indicates specific additives designed for particular laboratory analyses. There isn't a single "correct" color, as it depends entirely on the type of blood test being performed.
Which Color Blood Bottle is Used for Which Test?
The color of a blood collection tube cap signifies the additives or anticoagulants present within the tube, which in turn determine the type of tests that can be performed on the blood sample. Using the correct bottle ensures the integrity of the sample and the reliability of the test results.
The Importance of Correct Bottle Selection
Mismatched blood bottles can lead to erroneous test results, requiring redraws, delaying patient diagnosis, and potentially leading to incorrect treatment. Each additive plays a vital role in either preventing clotting, preserving cellular components, or facilitating specific chemical reactions needed for analysis.
Guide to Blood Bottle Colors and Their Uses
Here's a breakdown of common blood bottle colors, their primary uses, and the number of inversions required to ensure proper mixing of the blood with the additives:
| Color | Primary Tests | Inversions Required |
|---|---|---|
| Light Blue | Coagulation screen, INR, D-dimer | 3-4 |
| Yellow/Gold | U&E, CRP, LFTs, TFTs, Amylase, Calcium & phosphate, Magnesium, Lipid profile, Troponin | 5-6 |
| Purple | FBC, Blood film, ESR, HbA1c | 8-10 |
| Pink | Group and save, Crossmatch | 8-10 |
Detailed Explanation of Each Blood Bottle Type
Let's delve deeper into what each color signifies:
Light Blue Blood Bottles
- Additive: Sodium Citrate
- Purpose: Sodium citrate acts as an anticoagulant by binding to calcium ions, preventing blood from clotting.
- Common Tests:
- Coagulation Screen: Assesses the blood's ability to clot, including Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT).
- INR (International Normalized Ratio): Used to monitor patients on anticoagulant medication like warfarin.
- D-dimer: A marker used to help diagnose or rule out blood clotting disorders such as deep vein thrombosis (DVT) or pulmonary embolism (PE).
- Handling: Requires gentle inversions to ensure proper mixing without causing hemolysis (destruction of red blood cells), which can affect results.
Yellow/Gold Blood Bottles (Serum Separator Tubes - SSTs)
- Additive: Clot activator and gel separator
- Purpose: The clot activator speeds up blood clotting, and the gel forms a stable barrier between the serum and the blood cells after centrifugation. This preserves the serum for chemical analysis.
- Common Tests: These are widely used for biochemistry tests:
- U&E (Urea & Electrolytes): Measures kidney function and electrolyte balance (sodium, potassium, chloride).
- CRP (C-Reactive Protein): An indicator of inflammation.
- LFTs (Liver Function Tests): Assess liver health (e.g., ALT, AST, bilirubin).
- TFTs (Thyroid Function Tests): Measures thyroid hormone levels.
- Amylase: Used in the diagnosis of pancreatitis.
- Calcium & Phosphate, Magnesium: Essential mineral levels.
- Lipid Profile: Measures cholesterol and triglyceride levels.
- Troponin: A cardiac marker for heart muscle damage.
- Handling: Requires careful inversions to mix the clot activator without damaging the blood cells before clotting.
Purple (Lavender) Blood Bottles
- Additive: EDTA (Ethylenediaminetetraacetic acid)
- Purpose: EDTA is a potent anticoagulant that prevents blood from clotting by chelating (binding to) calcium, which is essential for the coagulation cascade. It helps preserve cellular morphology.
- Common Tests: These are primarily used for hematology tests:
- FBC (Full Blood Count): Measures red blood cells, white blood cells, and platelets, diagnosing conditions like anemia or infection.
- Blood Film: A microscopic examination of blood cells for abnormalities.
- ESR (Erythrocyte Sedimentation Rate): Measures inflammation.
- HbA1c (Glycated Haemoglobin): Used to monitor long-term blood glucose control in diabetes.
- Handling: Requires thorough inversions to ensure the EDTA mixes completely with the blood, preventing microscopic clots that could interfere with cell counts.
Pink Blood Bottles
- Additive: EDTA (Ethylenediaminetetraacetic acid)
- Purpose: Similar to purple bottles, EDTA in pink bottles prevents clotting to preserve red blood cells for blood typing and crossmatching.
- Common Tests: These are critical for transfusion medicine:
- Group and Save: Determines the patient's blood type and screens for unexpected antibodies, retaining the sample in case a crossmatch is needed.
- Crossmatch: Directly tests the patient's blood against donor blood to ensure compatibility before a transfusion.
- Handling: Similar to purple bottles, thorough inversions are essential for proper mixing and preservation of the blood sample for serological testing.
For more detailed information on blood bottle types and their applications, you can refer to comprehensive guides such as those found on Geeky Medics.
