Cap Color Blood Collection Tubes & Order of Draw

Overview

• Phlebotomy practice requires following a strict order of draw to avoid additive carry-over and specimen contamination.

• Each tube is identified by the color of its cap, the additive inside, the test categories it supports, and special handling (inversions, sterility).

Order of Draw (First ➜ Last)

1. Blood Culture (usually Yellow SPS bottles/tubes)

2. Light Blue

3. Red (glass or plastic)

4. Gold / Tiger Top (SST)

5. Green (light or dark)

6. Lavender (Purple)

7. Pink

8. Gray

Detailed Tube-by-Tube Guide

1. Blood Culture Tube

• Cap Color: Yellow (or culture bottles)

• Additive: Culture media that supports bacterial growth.

• Primary Use: Blood cultures to detect bacteremia / septicemia.

• Special Directions:
  • MUST be drawn first.
  • Use strict sterile technique (chlorhexidine or iodine skin prep).
  • Invert 3–4 times to mix.

2. Light Blue Tube

• Additive: \text{3.2\% or 3.8\% } \text{Sodium Citrate} (anticoagulant that binds Ca²⁺).

• Primary Use: Coagulation studies (PT, aPTT, D-dimer, fibrinogen, etc.).

• Mixing: Invert 3–4 times immediately after draw.

3. Red Tube (Glass or Plastic)

• Additive:
  • Glass: none (silicon-coated).
  • Plastic: Clot activator (silica particles).

• Primary Use: Chemistry tests requiring serum where gel separator is not desired (drug levels, hormone assays, etc.).

• Mixing: Invert 5 times.

4. Gold / Tiger Top (SST)

• Additive:
  • Clot activator +
  • Gel for Serum Separator ("thixotropic gel" that creates a physical barrier after centrifugation).

• Primary Use: Routine chemistry panels (BMP, CMP, lipid profile, liver function, etc.).

• Mixing: Invert 5 times.

5. Green Tube

• Additive Options: Sodium, Lithium, or Ammonium Heparin (antithrombin activator).

• Primary Use: Chemistry tests on plasma (cardiac enzymes, ammonia, electrolytes when rapid turnaround required).

• Mixing: Invert 8 times.

6. Lavender (Purple) Tube

• Additive: \text{K}_2 \text{EDTA} (chelator that binds Ca²⁺).

• Primary Use: Hematology (CBC, ESR), molecular diagnostics, Hemoglobin A1c.

• Mixing: Invert 8–10 times.

7. Pink Tube

• Additive: Spray-dried EDTA (same mechanism as lavender but meets immunohematology volume requirements).

• Primary Use: Blood bank testing—blood grouping and cross-matching.

• Mixing: Invert 8–10 times.

8. Gray Tube

• Additives:
  • Sodium Fluoride (glycolytic inhibitor)
  • Potassium Oxalate (anticoagulant)

• Primary Use: Glucose studies, lactate, blood alcohol levels.

• Mixing: Invert 8 times.

Key Practical & Safety Points

• Invert immediately after draw to ensure proper mixing with additives—failure can lead to clotting or inaccurate results.

• Sterility is mandatory only for blood cultures but good aseptic technique benefits all collections.

• Incorrect order can cause:
  • EDTA contamination ➜ falsely low Ca²⁺, falsely high K⁺.
  • Heparin contamination ➜ prolonged clotting times.
  • Clot activator carry-over ➜ microclots in anticoagulated specimens.

• Follow any institution-specific policies, but the color sequence above aligns with CLSI (Clinical & Laboratory Standards Institute) guidelines.

Memory Aids (Optional)

• "Boys Love Ravishing Girls Like Dieters Love Greek Yogurt" = Blood culture, Light blue, Red, Gold, Light green, Lavender, Gray.

Ethical & Quality Considerations

• Accurate phlebotomy prevents diagnostic error, supporting patient safety.

• Proper tube usage conserves healthcare resources by reducing repeat blood draws and patient discomfort.