Blood Collection Tubes and Order of Draw

Purpose: Blood cultures are used specifically to determine the presence of bacterial/fungi in the blood. They are typically utilized in cases of suspected infection or FUO (Fever of Unknown Origin).
Diagnostic Utility: These cultures help diagnose conditions such as sepsis, endocarditis, and meningitis.
Additive: Nutrient broth. If microorganisms are present, this broth promotes rapid growth for detection.
Laboratory Section: Microbiology.
Containers:
- Yellow SPS Tubes: These contain SPS (Sodium Polyanethole Sulfonate). SPS prevents blood from clotting and preserves bacteria or fungi for culturing.
- Blood Culture Bottles: These come in aerobic and anaerobic types. The draw sequence is aerobic followed by anaerobic.
Aseptic Technique: Requires a strict aseptic technique, including the disinfection of the collection site with ChloraPrep. This prevents environmental contamination.
Ordering: They are usually ordered as STAT or as timed draws.

Discard Tube (Red or Clear Top):
- Draw Sequence: This must be drawn before the light blue (citrate) tube.
- Purpose: It removes air contamination from the line, which could otherwise affect test results.
Light Blue Tube (Sodium Citrate):
- Additive: Sodium citrate.
- Purpose: Used for coagulation studies.
- Mechanism of Action: Sodium citrate prevents blood from clotting by binding to (chelating) $Ca^{2+}$ . This Ion is essential for the coagulation cascade.
- Yields: Plasma.
- Preservation Details: It preserves coagulation factors and allows $Ca^{2+}$ to be added back in later for clotting tests.
- Common Tests: PT (Prothrombin Time), INR, aPTT, D-dimer, and Fibrinogen.
- Laboratory Section: Coagulation.
- Specific Requirements:
  - Requires a precise ratio of $9$ parts blood to $1$ part sodium citrate.
  - The tube must be completely filled to ensure this ratio is maintained.
  - Inversion: $3$ to $4$ times.

Red Top Tube:
- Glass Red Top: Contains no additive. Inversion is not required.
- Plastic Red Top: Contains a clot activator.
- Mechanism: Blood is allowed to form a clot, which produces serum.
- Uses: Commonly used for chemistry and hormone tests.
Tiger / Marble / Gold Tube (SST - Serum Separator Tube):
- Additives: Silica (clot activator) and separator gel.
- Mechanism: Silica promotes rapid clot formation. The separator gel forms a physical barrier between the cells and the serum during centrifugation to prevent contamination.
- Yields: Serum.
- Laboratory Section: Chemistry.
- Inversion: $5$ to $8$ times.
- Common Uses: BMP (Basic Metabolic Panel), CMP (Comprehensive Metabolic Panel), serum pregnancy tests, and lipid or cholesterol panels.

Light Green Tube (PST - Plasma Separation Tube):
- Additives: Lithium heparin and thixotropic (separator) gel.
- Mechanism of Action: Heparin inhibits clotting by binding to antithrombin, inducing a conformational change that makes antithrombin more effective. This results in the inhibition of the coagulation cascade.
- Yields: Plasma.
- Laboratory Section: Chemistry.
- Inversion: $8$ times.
- Advantages: Highly useful in time-sensitive situations because there is no need to wait for the blood to clot before processing.
- Restrictions: Heparin interferes with blood smears, so it cannot be used for hematology tests.
- Common Uses: STAT electrolytes and hCG.
Dark Green Tube:
- Additive: Heparin (Li, Na, or $NH_4$ ).
- Mechanism: Functions similarly to the light green tube by inhibiting thrombin and the coagulation cascade, but it does not contain a separator gel.
- Yields: Plasma.
- Laboratory Section: Chemistry.
- Inversion: $8$ times.
- Common Uses: Chemistry tests, Ammonia tests (which must be placed on ice), and Liver function tests.

Pink Tube (Blood Bank):
- Additive: EDTA ( $K_2EDTA$ ).
- Mechanism: EDTA binds $Ca^{2+}$ to inhibit the coagulation cascade. This binding is irreversible, meaning the tube cannot be used for coagulation studies.
- Yields: Plasma.
- Laboratory Section: Blood Bank.
- Inversion: $8$ times.
- Key Quality: Excellent at preserving cell morphology and antigen expression. It allows for accurate blood bank testing without dilution.
- Common Tests:
  - Type & Screen: Provides knowledge of blood type and existing antibodies.
  - Cross Match: Used to determine donor blood compatibility.
- Requirement: The tube must be at least $2/3$ full.
Lavender Tube (Hematology):
- Additive: EDTA ( $K_2EDTA$ ).
- Mechanism: Same as pink; inhibits coagulation and preserves cell morphology.
- Yields: Plasma.
- Laboratory Section: Hematology.
- Inversion: $8$ times.
- Usage Notes: Used for hematology tests that analyze the cellular components of blood. These tubes should not be centrifuged.
- Common Tests: Complete Blood Count (CBC), Hemoglobin, Hematocrit, and Blood smear.

Gray Tube:
- Additives:
  - Potassium Oxalate: Binds calcium to inhibit the coagulation cascade.
  - Sodium Fluoride: An antiglycolytic agent that prevents glycolysis to preserve glucose levels.
- Yields: Plasma.
- Laboratory Section: Chemistry.
- Inversion: $8$ times.
- Common Tests: Oral Glucose Tolerance Test (OGTT), Lactic acid, and Alcohol.
Royal Blue Top Tube:
- Variants:
  - With Red Stripe: Drawn after the light blue tube; contains no additive and yields serum.
  - With Blue or Lavender Line: Drawn after the lavender tube; contains EDTA and yields plasma.
- Inversion: $8$ times for the version containing EDTA.
- Laboratory Section: Toxicology.
- Common Tests: Lead (Pb) poisoning and heavy metal analysis.