Blood Tests and Their Corresponding Collection Tubes

Correct blood collection tubes are critical because the wrong tube can completely invalidate a test result. Each tube contains specific additives that either prevent clotting, preserve cells, or stabilize chemicals.

Common Blood Collection Tubes (Quick Overview)

Hematology Tests and Tubes

Lavender / Purple Top (EDTA Tube)

Used for cell counting and morphology.

Tests include:

• Complete Blood Count (CBC)

• Hemoglobin (Hb)

• Total RBC Count

• Total WBC Count

• Differential Leukocyte Count (DLC)

• Platelet Count

• Peripheral Blood Smear

• Reticulocyte Count

• HbA1c

• MCV, MCH, MCHC

• Hematocrit (PCV)

• Sickling Test

📌 Why EDTA?
It preserves blood cells and prevents clotting without altering cell structure.

Coagulation Tests and Tubes

Light Blue Top (Sodium Citrate Tube)

Used for clotting studies.

Tests include:

• Prothrombin Time (PT)

• INR

• Activated Partial Thromboplastin Time (APTT)

• D-Dimer

• Fibrinogen

• Coagulation Factor Assays

📌 Important: Tube must be filled exactly to the mark to maintain correct blood-to-anticoagulant ratio.

ESR Test

Black Top Tube (Sodium Citrate – ESR specific)

Test:

• Erythrocyte Sedimentation Rate (ESR)

📌 Specifically designed for ESR testing only.

Biochemistry Tests and Tubes

Yellow Top (SST – Serum Separator Tube)

Used for most routine biochemistry and hormone tests.

Tests include:

• Liver Function Test (LFT)

• Kidney Function Test (KFT)

• Lipid Profile

• Thyroid Function Test (T3, T4, TSH)

• Uric Acid

• Calcium

• Phosphorus

• Magnesium

• Total Protein, Albumin

• Bilirubin

• Amylase, Lipase

• Vitamin D

• Vitamin B12

• Iron Studies

• Tumor Markers (PSA, CA-125, CEA, AFP)

• Cardiac Markers (Troponin, CK-MB)

📌 Gel separates serum from cells after centrifugation.

Red Top Tube (Plain Tube)

Used when serum is required without gel.

Tests include:

• Serology tests

• Drug levels

• Therapeutic drug monitoring

• Hormone assays (when SST not preferred)

• Blood bank cross-matching (in some labs)

Blood Sugar Tests

Grey Top Tube (Fluoride Oxalate)

Tests include:

• Fasting Blood Sugar (FBS)

• Postprandial Blood Sugar (PPBS)

• Random Blood Sugar (RBS)

• Glucose Tolerance Test (GTT)

📌 Sodium fluoride prevents glucose breakdown.

Electrolyte & Emergency Tests

Green Top (Heparin Tube)

Tests include:

• Electrolytes (Na⁺, K⁺, Cl⁻)

• Blood Gases

• Ammonia

• Lactate

• Emergency biochemistry panels

📌 Preferred in ICU and emergency settings.

Immunology & Serology Tests

Yellow or Red Top Tubes

Tests include:

• HIV

• HBsAg

• Anti-HCV

• Dengue (NS1, IgG, IgM)

• Widal Test

• VDRL

• CRP

• ASO

• RA Factor

• ANA

• COVID-19 antibody tests

Blood Bank & Transfusion Tests

Pink Top (EDTA – Blood Bank Tube)

Tests include:

• Blood Grouping (ABO & Rh)

• Cross Matching

• Antibody Screening

• Coombs Test (Direct & Indirect)

📌 Specially labeled for transfusion safety.

Trace Elements & Toxicology

Royal Blue Top Tube

Tests include:

• Lead

• Mercury

• Arsenic

• Zinc

• Copper

• Selenium

📌 Tube is contamination-free for accurate trace analysis.

Molecular & Genetic Tests

White Top (PPT Tube – EDTA + Gel)

Tests include:

• PCR tests

• Viral load (HIV, Hepatitis B & C)

• Genetic mutation analysis

• COVID-19 RT-PCR (blood-based)

Special Hormone Tests

Yellow / Red Top Tubes

Tests include:

• Cortisol

• Insulin

• Prolactin

• LH, FSH

• Testosterone

• Estrogen

• Progesterone

Quick Memory Tip (Order of Draw)

1. Blood culture bottles

2. Blue (Citrate)

3. Red

4. Yellow (SST)

5. Green

6. Lavender / Pink

7. Grey

Conclusion

Knowing which blood test goes into which tube is not just a technical detail—it directly affects accuracy, diagnosis, and patient safety. Using the wrong tube can lead to false results, repeat sampling, delayed diagnosis, and even treatment errors. This knowledge is essential for phlebotomists, lab technicians, nurses, medical students, and clinicians.