ZRL tube guide

Use this quick reference guide to identify which tubes are appropriate for Zoetis Reference Laboratories (ZRL) sample collection based on sample type and common test usage. For detailed instructions on how to prepare and submit your sample, please refer to the collection guidelines specific to your sample type.

Tube Type Additive Sample Type(s) Tube Description Common Uses

Blue-top tube

Blue dotBTT

Test tube with blue cap

3.2% sodium citrate anticoagulant

Plasma

Light blue top

  • Microtainer also available for low-volume samples (very small, pediatric, and exotic species)

Coagulation testing (PT, aPTT, factor assays)

Purple-top or lavender-top tube

Lavender dotLTT

Test tube with lavender cap

Potassium EDTA anticoagulant

Whole blood/EDTA whole blood or plasma (EDTA plasma is rarely used)

Purple or lavender top

  • Microtainer also available for low-volume samples (very small, pediatric, and exotic species)

Most common use:

  • Whole blood for CBC

Green-top tube

Green dotGRNTT

Test tube with green cap

Lithium heparin anticoagulant may be present as a floating disc in the tube

Whole blood or plasma

Green top

  • Microtainer also available for low-volume samples (very small, pediatric, and exotic species)

Most common use:

  • Free (ionized) calcium, whole blood for point-of-care chemistry testing

Other uses:

  • Plasma sometimes used for various tests for pediatrics and small exotic species

Mint- or light-green-top microtainer

Mint light green dotM-GRNTT

Small container with mint light green cap

Lithium heparin anticoagulant (either sprayed into tube or in gel)

Plasma

Mint- or light-green-top microtainer

  • Opaque, light yellow gel at bottom of tube

  • Differs from green-top tube in that it contains a gel additive that separates RBCs from plasma when centrifuged

Most common use:

  • Plasma for point-of-care chemistry testing (often reserved for use with very small, pediatric, and exotic species)

Red-top tube

Red dotRTT

Test tube with red cap

Clot activator (sprayed inside of tube)

Serum

Red top with chalky residue (clot activator) in tube

Please note: No-additive RTTs are also available. Tubes with clot activator should not be used when a no-additive tube is required.

Most common use:

  • Serum chemistry testing

Other uses:

  • Immunology

  • Serology

  • Many others

Serum-separator tube or tiger-top tube or gold-top tube

White dot with red outlineSST

Tube with red cap

Clot activator (embedded in gel)

Serum

Red top, red and black marble top (tiger top)

  • Gold-top microtainer also available for low-volume samples (very small, pediatric, and exotic species)

  • Important not to confuse gold-top tube with yellow-top urine tube

  • All tubes have opaque light yellow gel at bottom of tube

Most common use:

  • Serum chemistry testing

Other uses:

  • Immunology

  • Serology

  • Many others

White-top tube

White dotWTT

Test tube with white cap

No additive

Serum

White top (no additive)

Used when serum needs to be separated from RBCs and removed from original collection tube to avoid prolonged contact with RBCs or separator gel

  • Used when special handling of sample required (such as freezing)

  • Often used for collection of fluids/ urine and materials for culture

Yellow-top tube

Yellow dogUrine

Test tube with yellow cap

No additive

Urine

Bright yellow top

  • May have a conical or tapered base

Urine for urinalysis and other various tests