Types of Blood Samples, Criteria for rejection of the blood sample, Color coding of the blood sample tubes

Blood samples types:

1. The blood sample from the patients is of various types according to the type of blood tests.
2. These blood sample timings are also critical, and some of the tests may need a fasting sample, while some tests may be done on random samples.
   

   Types of blood samples

1. Venous blood:
   1. This is the easiest way to collect the blood sample.
   2. It is free of complications.
   3. Blood is taken from the superficial veins.
   4. The commonest site is the antecubital fossa because of the presence of basilic vein, cephalic vein, median cubital veins are the commonest veins.
      1. Veins of the wrist or hand may be used.
      2. Another site is the femoral vein.
         

         Venous blood sites on the arm

2. Arterial blood:
   1. Arterial blood is used to measure arterial blood gases, like oxygen, CO2, and pH.
   2. Arterial puncture is more difficult than the venous sample.
   3. The Brachial and radial arteries are often used; the femoral artery is usually avoided because of bleeding.
3. Capillary blood:
   1. It is mostly used in the pediatric patient’s group where there is no need for a large amount of blood.
   2. The common sites are the fingertips, heel, and ear lobe. The heel is most commonly used in infants.
      

      Capillary blood procedure sites

Criteria for the rejection of the blood sample:

1. Blood samples are not labeled or not properly labeled.
2. Insufficient blood quantity.
3. Blood sample showing hemolysis.
4. A wrong collection tube is used.
5. Insufficient quantity of the anticoagulants.
6. Improper transport of the sample.

Nowadays, there are commercially color-coded tubes available:

• The following table shows their color and the purpose of the use:
  

  Stopper tube	Additives	Outcome of additive	Purpose of use	Test tubes
  Red	N0 anticoagulant No additives	For serum	Chemistry Serology Blood banking
  Lavender	EDTA	Anticoagulant, for plasma Remove calcium and prevent clotting. Invert tube 6 to 8 times	CBC CEA Best for hematology
  Orange	Thrombin	Accelerate clot usually in 5 minutes, for serum formation It should be inverted 8 times.	All serum test Chemistry
  Light Blue	Sod. Citrate	anticoagulant binds calcium. Get blood or plasma	Coagulation studies PT, APTT, factor assay
  Gray	Na fluoride/K oxalate	Inhibit glycolysis Anticoagulant, remove Ca++ to prevent clotting. Get whole blood or plasma.	Glucose GTT Alcohol level
  Green	Na+ Heparin Lithium Heparin Ammonium Heparin	Inhibit thrombin activation to prevent clotting. Get whole blood or plasma. Invert the tube 7 to 10 times to prevent clotting	Ammonia level Arteria blood gases Carboxy Hb Lead Plasma chemistry Hormones Electrolytes
  Yellow	Na+polyanetholesulfate	Prevent blood from clotting Stabilize bacterial growth Invert the tube 8 times to prevent clotting	Blood culture
  Glod	Gel-separator Clot activator	Clot activator shortens the time for clot formation. The gel forms a separator between cells and serum. Invert tube 5 times and centrifuge after the clot formation	Most chemistry tests Not good for blood banking
  Light green	Gel separator Lithium heparin	Heparin prevents clotting The gel prevents cell contamination.	Potassium determination
  Black	Na + citrate	Binds  Ca++ 4:1 ratio of blood to anticoagulant	Westgreen ESR determination

Summary of the color-coded blood collection tubes:

1. Red top tube = No additives for chemistry tests.
2. Blue top = Coagulation studies.
3. Green top = For general purpose, blood gases, chemistry.
4. Lavender top = For CBC and hematology.
5. Gray top = For chemistry and glucose.
6. Yellow top = For blood culture.

Contents difference between plasma and Red blood cells:

Contents	Plasma	Red Blood Cells
Glucose mg/dL	90	74
Uric acid	4.6	2.5
Nonprotein nitrogen mg/dL	8.0	40
Cholesterol mg/dL	194	139
K+ meq/L	4.4	100
Na+ meq/L	140	16
Ca2+ meq/L	5.0	0.5
Cl– meq/L	104	52
HCO3– mmol/L	26	19
LDH  units	360	58000
Transaminase	25	500

• Above is a picture presentation of test tubes.

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