Reasons behind Haemoglobin test

Testing of blood donors for hemoglobin before donation is very important to determine whether the donor, males or females, is fit to donate blood.  Drugs & Cosmetic Act permit blood banks to collect blood only when the donor has h hemoglobin level of 12.5 gm/dl.  That means no blood bank should take blood from the donors who has hemoglobin less than 12.5 gm/dl.  And, donor should undergo hemoglobin test every time he/she donates blood.  If any of the blood banks violates this rule, they can be punished.

The basic concept is that we should not deprive or harm the donor and at the time, should benefit the recipient that is patient. No harm is done to the donor if he has 12.5 gm/dl and has a weight of 45 Kgs or above.  And, hemoglobin of 13.5 g/dl is required for a donor to donate 2 units of red cells by apheresis method.

Scientifically speaking a donor having minimum hemoglobin of 12.5 gm/dl can tolerate removal of 1 gm of hemoglobin along with one unit of blood (350 or 450 ml).  This loss is regained to the donor within a month period.  But, however, to give adequate time for recovery, a minimum of 3 months, is given to the donor for recovery and next donation. 

 If a donor has hemoglobin more than 16 gm/dl, he may be suffering from polycyethemia meaning excess red cells and hemoglobin.  Excess red cells lead to thicker blood.  This condition is technically called hyper-viscosity.  Thicker blood does not flow well into the micro-circulation.  Polycythemia may be a prelude to blood cancer.  Hence, blood collected from polycythemia is not used for transfusion.  Blood banks doing quantitative test counsels the donor to consult a physician.

Hemoglobin test method:  There are several methods available.  The simple method is by specific gravity method by using copper sulphate solution adjusted to specific gravity of 1.053, which corresponds to 12.5 g/dl.  This method is especially useful in blood donation camps where there is large number of donors.  However, this method will not detect exact level of hemoglobin.  It can detect only whether blood has 12.5 gm/dl or not.  Hence, it is a semi-quantitative method. So, it cannot detect polycythemia and there are chances of blood from polycythemia patient going to the patient.

Cyanmethoglobin method is accurate but time consuming.  It is suitable in blood banks and when there is less number of donors to attend.

Portable and handy equipments are available, which uses strips recoated with reagent.  The blood is applied over to the strip and then inserted in to the equipment.  Within a minute there will be a digital display of the result.  The donor gets the satisfaction of knowing his/her hemoglobin level on the spot. Only disadvantage of this method is it is costly.  Slowly blood banks are switching over to this method.