When collecting blood sample for biochemical analysis, the specimens containers used to collect the blood must be leak proof and biologically and chemically clean, needle and syringe also must be free of all contaminants, either biological or chemical, and must be sterile.

The most acceptable method of collecting blood sample for biochemical analysis, is via venepuncture.

Some variable that often found to affect the final result are often trace to blood collection procedure, some of these factors are;

1. Wrong Venepuncture procedure

2. Hemolysis of red blood cells

3. Using wrong blood containers

4. Present of some instability substance in the blood.

The used of disposable syringe and needle limit the rate of risk of infection, as a result of serum hepatitis virus (HV) and human immunodeficiency virus (HIV).

It is recommended to used plastic tubes and bottle instead of glass apparatus, to minimize the risk rate of these transmitted disease.

Venepuncture procedure

Is simpler to enter a vein that can be felt than a vein that can only be seen. Be careful in collecting Venus blood, the tourniquet should not be applied too loose or too tight, because any of it can led to Venus stasis, which cause the concentration of certain components of blood, such as hemoglobin, plasma protein and calcium.

Many young scientists are often guilty of these, is totally wrong and unacceptable to collect sample from the arm which infusion is already been given to patient or arm which infusion is on going.

Hemolysis of Red blood cells

Normally red blood cells are not used for biochemical analysis, because ruptures of red blood cells can yield false result. Mechanism behind it, is that hemolysis cause substance from the cells to be injected into the serum or plasma as such yield fault increased of the concentration of substance to be analyzed.

Below are tips to follow to avoid hemolysis

1. Good, clean, dry, sterile syringe and needle should be used.

2. Blood sample should be withdrew slowly and steadily.

Give enough time for the blood to clot and clot retraction to take place.

1. Try as much as possible to avoid prolonged centrifugation, centrifuge of 3 to 5 minute at 700g is enough.

2. Never shake blood sample, always mix blood gently and evenly, if the container have anticoagulant.

3. Never freeze whole blood samples.

4. Never keep the blood near hot object, or place it in hot object.

Specimen containers

Often, biochemical analysis, are carried out on serum. As such blood is collected into a dry clean containers. But here are some test that is carried out with plasma, in case test are to be carried out with plasma, blood is collected into anticoagulant container’s to prevent the blood to clot and from there plasma can be collected after centrifugation that separate the plasma with the red blood cells. When the need be, is more advantageous in using plasma instead of serum, because the volume of plasma given out from the whole blood is higher than that of serum, and investigation can be done instantly. Lithium heparin is the most suitable anticoagulant used for biochemical analysis because it did not interfere with the chemical reaction, it aid in reducing the action of hemolysis, and did not have sodium or potassium salt that might interfere when analysing electrolyte. But lithium heparin is very cost as such, another anticoagulant such as EDTA (ethylene diamine tetra acetic acid) and fluoride oxalates are used widely despite it contains sodium and potassium salts.

Note; fluoride is an enzyme inhibitor that inhibit glycolysis (breakdown of glucose to lactic acid by action of enzymes), as such the anticoagulant should not be used when enzyme activities are to be analyzed.

Preservation of blood

Chemical substance present in the blood are found in the plasma and serum in a different quantities, as such quickly separation of plasma from cells is necessary in other to inhibit chemical change that can take place in the whole blood. Storages of blood specimens in the refrigerator before separation can yield false high potassium level. When fluoride oxalate anticoagulant is not use, it can lead to glycolysis. Bilirubin’s decompose on a prolonged exposure to light. It is good to refrigerate serum or plasma at 4°C or freeze at -20°C pending when analysis is to take place.

Finally, try as much as you can to handle blood sample septically to reduce the rate of contamination by bacteria and other microorganisms.