Blood collection tubes, also known as vacutainer tubes, come in various types, each with a specific additive or anticoagulant for different tests. Here’s a breakdown of the main types of blood collection tubes and their uses:

Red Top Tube (No Additive)

1. Additive: None.
2. Use: Primarily for serum collection in tests like chemistry, serology, and immunology. The blood clots naturally, and the serum is separated after centrifugation.
3. Common Tests: Hormones, drug levels, blood typing, infectious disease testing.
4. Note: Sometimes silica particles may be added as a clot activator.

Gold Top / Yellow Top (SST - Serum Separator Tube)

1. Additive: Gel separator and clot activator.
2. Use: Similar to the red-top tube, but the gel forms a barrier between the serum and cells after centrifugation, improving serum quality.
3. Common Tests: Same as red top, but with the added convenience of serum separation.

Light Blue Top Tube

1. Additive: Sodium citrate (anticoagulant).
2. Use: For coagulation studies by preventing the blood from clotting.
3. Common Tests: Prothrombin time (PT), Activated Partial Thromboplastin Time (aPTT), D-dimer, coagulation factor assays.
4. Note: Requires precise blood-to-additive ratio, so the tube must be filled completely.

Lavender or Purple Top Tube

1. Additive: EDTA (Ethylenediaminetetraacetic acid) as an anticoagulant.
2. Use: Prevents clotting by binding calcium, used for whole blood or plasma testing.
3. Common Tests: Complete Blood Count (CBC), blood smears, hemoglobin A1C, blood typing, and molecular diagnostics.
4. Note: It preserves the shape of blood cells, making it ideal for hematology.

Green Top Tube

1. Additive: Heparin (either lithium or sodium heparin).
2. Use: For plasma testing in chemistry, as it prevents clotting without interfering with many tests.
3. Common Tests: Electrolytes, liver function tests, ammonia levels, glucose, ionized calcium.
4. Note: Heparin works by inhibiting thrombin, stopping the clotting process.

Gray Top Tube

1. Additive: Sodium fluoride (antiglycolytic agent) and potassium oxalate (anticoagulant).
2. Use: Used for glucose testing and lactate levels, as sodium fluoride prevents glycolysis (breakdown of glucose by cells).
3. Common Tests: Blood glucose, lactate, and blood alcohol levels.
4. Note: This tube preserves glucose for up to 24 hours.

Light Yellow Top Tube (ACD - Acid-Citrate-Dextrose)

1. Additive: Acid-Citrate-Dextrose.
2. Use: Used in DNA testing, HLA typing, and preserving blood for tissue typing.
3. Common Tests: Genetic testing, paternity testing, organ transplant compatibility testing.
4. Note: It stabilizes red blood cells, making it useful for long-term preservation.

Dark Blue Top Tube (Trace Element Tube)

1. Additive: Either no additive or sodium EDTA.
2. Use: For toxicology and trace element testing, as these tubes are specially designed to avoid contamination with trace metals.
3. Common Tests: Heavy metal testing (lead, zinc, copper, mercury).

Pink Top Tube

1. Additive: EDTA (same as lavender, but more volume).
2. Use: Mainly for blood banking purposes.
3. Common Tests: Crossmatching, blood typing, antibody screening.
4. Note: Labeled specifically for blood bank testing and patient identification.

Black Top Tube

1. Additive: Sodium citrate.
2. Use: For erythrocyte sedimentation rate (ESR).
3. Common Tests: Sedimentation rate.
4. Note: The ratio of blood to sodium citrate in black tubes is different from light blue tubes, specifically calibrated for ESR testing.

Yellow Top Tube (SPS - Sodium Polyanethol Sulfonate)

1. Additive: Sodium Polyanethol Sulfonate (SPS).
2. Use: For blood cultures, as the SPS preserves microorganisms and prevents bacterial growth from being hindered.
3. Common Tests: Blood cultures for infection diagnosis.

Each type of blood collection tube is color-coded to indicate the type of additive and the tests for which the tube is suited, ensuring that the proper sample is collected for the correct test.