Blood Collection Tubes

A blood collection tube is sterile glass or plastic test tube with different colored cap. Blood collection tube contains an additive that either accelerates clotting of blood (clot activator) or prevents the blood from clotting (anticoagulant). Serum is separated from blood in a tube which contains clot activator and plasma is separated in a tube which contains an anticoagulant. Most laboratory tests are performed on serum, anticoagulated plasma or whole blood.

Most laboratory tests are performed on serum, anticoagulated plasma or whole blood. Please see the individual test directory listings for specific requirements. The tubes should be filled with the proper amount of blood for the size of tube used. Tubes with various draw volumes are available (2.0 mL, 3.0 mL, 5.0 mL and 0.75 mL microvettes); to assure proper ratio of EDTA to blood, it is recommended that the tubes contain no less than one-half of the stated volume. The supernatant is plasma after centrifuge.

Plasma:

Plasma is the liquid portion of blood which makes upto 55% of blood. It is mostly water and contains important proteins, glucose, clotting factors, electrolytes and enzymes. Plasma's main functions is the removal of waste from cellular functions that help to produce energy. Plasma accepts and transports this waste to other areas of the body, such as the kidneys or liver, for excretion. Blood plasma is separated from the blood by centrifuging the tube which contain fresh blood with anticoagulant.

Serum:

Serum is liquid part of blood after coagulation. Serum does not contain white or red blood cell or clotting factor. Fibrinogen is absent in serum.  Serum is obtained by centrifuging whole blood in a tube which does not contain any anticoagulant.

Serum = Plasma - Fibrinogen

Anticoagulants:

Anticoagulants are the chemical substances which prevent or reduce coagulation of blood. It is also known as blood thinners.

Example:- Heparin, dicoumarin, ivaroxaban,dabigatran, apixaban, EDTA ( Ethylene diamine tetraacetic acid).

Color codes of blood collection tube:

1.  Purple / Lavender top tube :-

• It contain EDTA ( Ethylene diamine tetraacetic acid) as anticoagulant.
• After the tube has been filled with blood, immediately invert the tube 8-10 times to mix and ensure adequate anticoagulation of the specimen.

Tube used for :-

• Blood films for abnormal cells or Malaria parasites
• ESR (Erythrocytes Sedimentation Rate)
• PTH (Parathyroid Hormone)
• CBC (Complete Blood Count)
• Red cells folate
• Reticulocytes
• Monospot test for EBW
• HbA1C

2.  Red top tube :-

• No additive present present in this tube.
• Blood clots in this tube and serum is separated by centrifugation.

Tube used for :-

• Lipid Profile
• Serology tests
• Therapeutic drug monitoring
• Blood bank
• Immunology

3.  Blue top tube :-

• It contains  Sodium Citrate (Blood : Anticoagulent ratio is 9:1). It acts as a reversible anticoagulent by binding to Calcium ions in the blood and disrupt the clotting cascade.
• The blue bottle needs to be inverted 3-4 times to mix the sample with the anticoagulant.

Tube used for :-

• BT (Bleeding time) for Platelets function
• PT (Prothrombin time) for Extrinsic pathway
• APTT (Activated Partial Thromboplastin Time)
• APTT ratio for monitoring patients on IV heparin infusion
• Fibrinogen assay
• Anti-Xa assay
• D-dimer test for thrombosis
• INR for monitoring patient on Warfain
• Other blood coagulation tests

4.  Pink-top tube :-

• This tube contains EDTA as an anticoagulant. These tubes are specifically used for whole blood samples being sent to the transfusion lab.
• After the tube has been filled with blood, immediately invert the tube 8-10 times to mix and ensure adequate anticoagulation of the specimen.

Tube used for :-

• Cross match
• Direct Coomb’s test
• Group and save (G&S)

5.  Yellow-top tube :-

• This tube contains ACD, which is used for the collection of whole blood for special tests.
• This tube is known in the lab as the SST (serum separating tube). It contains two agents. One is  silica particles and another is serum separator. Silica particles work to activate clotting and cause the blood cells to clump together. The serum separator consists of an inert polymer gel which floats as a layer between the blood cells and plasma to form a physical barrier between them. This means that the sample can be centrifuged (spun) in the lab and the separated serum easily removed.
• The yellow bottle needs to be inverted about 5 times to mix the sample with the silica and separator.

Tube used for :-

• Vitamins
• Urea and electrolytes like Na, Ca, K, Iron
• C-reactive protein (CRP)
• Lipid profile
• Liver function tests (AST, ALT, Bilirubin
• Bone profile
• Thyroid function tests (TFTs)
• Troponins

6.  Grey-top tube :-

• This tube contains potassium oxalate as an anticoagulant and sodium fluoride as a preservative. It is used to preserve glucose in whole blood and for some special chemistry tests.
• After the tube has been filled with blood, immediately invert the tube 8-10 times to mix and ensure adequate anticoagulation of the specimen.

Tube used for :-

• Glucose
• Lactate

7.  Dark green-top tube :-

• This tube contains sodium heparin used for the collection of heparinized plasma or whole blood for special tests.
• After the tube has been filled with blood, immediately invert the tube 8-10 times to mix and ensure adequate anticoagulation of the specimen.

Tube used for :-

• Chromosomal tests
• Ammonia
• Aluminium
• Insulin
• Renin and aldosterone

8.  Light green-top tube :-

• This tube contains lithium heparin and gel separator used for the collection of heparinized plasma for routine chemistry tests.
• After the tube has been filled with blood, immediately invert the tube 8-10 times to mix and ensure adequate anticoagulation of the specimen.

Tube used for :-

• Routine biochemistry