Blood collection tubes

Sodium Citrate (light blue top tube)

• Definition :

  • It contains 3.2% sodium citrate as its anticoagulant.

    
    

• Mechanism of action:

  • Sodium citrate prevents coagulation by binding calcium and preserves the unstable coagulation factors.

  • Must be drawn prior to collection of serum tubes to prevent contamination with clot activator and interference with coagulation cascade.

  • The citrate tube must be accurately filled to the mark to obtain a mixing ratio of one part citrate to nine parts blood.

    
    

• Uses:

  • Blood coagulation test and applicable to the fibrinolysis systems like PT, TT, APTT and fibrinogen, etc.

    
    

• Disadvantages:

  • Form a complex with molybdate , thus it decrease the color yield in Phosphate measurements that involve molybdate ions, hence producing low results.

  • Unsuitable for assay of calcium

    Serum Gel (yellow top tube)

    
    

    
    

• Definition:-

  • They contain a special gel that separates blood cells from serum, as well as particles to cause blood to clot quickly. The blood sample can then be centrifuged, allowing the clear serum to be removed for testing.

    
    

• Uses:-

  • Used for separation and examination of blood serum.

  • They can improve serum surface and prevent blood substance exchange between blood cell and serum.

    
    

• Mechanism of action:-

  • Tube walls is coated with silicon layer which causes faster clotting blood specimen and avoiding hemolysis effect.

  • Gently invert tube to activate clotting; let stand for 20 to 30 minutes before centrifuging for 10 minutes.

  • If frozen serum is required, aliquot off serum into plastic vial, label properly, and freeze. Do not freeze serum gel tube.

    
    

    Serum (Red top tube) Blood

    
    

    
    

• Definition:-

  • Red-top tube: Contains no anticoagulant or preservative.

  • The inner wall of each serum tube is coated with microscopic silica particles (clot activator main component SiO2) which activate clotting when the tubes are carefully turned.

    
    

• Use:-

  • Serum tubes are used in determinations for clinical chemistry and immunology, hormones and microbiological serology.

    
    

• Mechanism of action:-

  • These tubes have silica particles, which activate clotting.

    Serum must be separated from cells within 45 minutes to two hours depending on the tests

    
    

    Heparin (green top tube)

    
    

    
    

• Definition:-

  • Heparin is the most widely used anticoagulant that contain spray-dried lithium, sodium or ammonium heparin on the inner walls.

  • Just 0.2 mL of sodium (lithium) heparin (1000 IU/mL) added to 5 mL of blood will give a final heparin concentration of 40 IU/mL blood, sufficient for anticoagulation.

    
    

• Mechanism of action:-

  • The anticoagulant heparin activates antithrombin, which blocks the clotting cascade and thus produces a whole blood/plasma sample.

    
    

• Uses:-

  • Used for specialized hematology studies, such as red cell fragility tests and several specialized chemistry tests.

    
    

• Disadvantages:-

  • Inhibits acid phosphatase activity.

  • Affects the binding of triiodothyronine and thyroxin to their carrier proteins, producing higher free concentration of these hormones.

    
    

    
    

    Ethylenediaminetetraaacetic acid (EDTA)

    
    

    
    

    
    

• Definition

  • EDTA tubes can be contain either (K2EDTA or K3EDTA).

  • EDTA is used as disodium, dipotassium or tripotassium salts, and the latter two being more soluble.

    
    

• Mechanism of action

  • EDTA prevents coagulation by binding calcium, which is essential for clotting mechanism.

    
    

• Uses

  • EDTA is used in hematology procedures such as: blood count

    
    

• Disadvantages

  1. Chelation of calcium makes EDTA unsuitable for calcium and iron analysis using photometric or titrimetric methods.

  2. Higher concenterations hypertonically shrink the red cells

  Sodium fluoride (Gray- top tube)

  
  

  
  

• Definition:

  • This tube contains potassium oxalate as an anticoagulant and sodium fluoride as a preservative- used to preserve glucose in whole blood and for some special chemistry tests.

• Mechanism of action:

  • It exerts its preservative action by inhibiting the enzyme systems involved in glycolysis.

  • After tube has been filled with blood, immediately invert tube several times in order to prevent coagulation.

    
    

• Uses :

  • It measures the Glucose levels in the blood.

    1. Random blood sugar level.

    2. Fasting blood glucose.

    3. Postprandial blood glucose

    
    

• Disadvantages :

  • It is poorly soluble, thus blood must mixed thoroughly for effective antiglycolysis to occur.

    ESR citrate tube

    
    

    
    

• Definition:-

  • ESR Tube is used in blood collection and anticoagulation for sedimentation rate test. It contains a 3.8% buffered tri-sodium citrate solution (0.129mol/l) with the mixing ratio of 1 part citrate solution to 4 parts blood. ESR measurement refers to the Westergren method

    
    

• Uses:

  • ESR tubes measure the rate at which red blood cells settle out of plasma

    
    

• Mechanism of action :

  • Drawing blood in a liquid sodium citrate tube, or using a saline-diluted EDTA tube and mix well 6 – 10 times.

  
  

• Disadvantages :

• When ESR is tested manually, incorrect results are obtained if the ESR test tube is not stood strait-up and vertically