I am posted to the biochemistry/clinical chemistry section of my lab for 2 weeks. For this 2 weeks, I have been doing 2 kinds of major test on EDTA-coagulated blood specimens. One is G6PD and the other is HbA1c Quantitation. I will be putting up a post regarding HbA1c Quantitation.
At the end of my first week, I have learnt a new constituent in the blood, which can be tested. It is HbA1c or Glycosylated (or glycated) hemoglobin. Glucose in the blood stream will normally be attracted to the haemoglobin part at the lysine molecule of the RBC to form glcosylated haemoglobin. Thus the amount of HbA1c is directly proportional to amount of glucose, meaning that if there are more glucose present in the blood, the more HbA1c will be present in the blood. It’s a known fact htat RBC has a half-life of about 3 months before they are replaced by the spleen. Hence by measuring the percentage of HbA1c in the blood, we can determine how high the patient’s blood glucose has been on average over the last 3 months.
Currently HbA1c is the best suitable way to monitor the progress of medication for patients suffering from diabetes mellitus. It is also able to determine the appropriate dosage quantity of anti-diabetic drugs do administer to patients so as to effectively reduce glucose blood level and reduce possible side-effects.
I am now working in a company who uses a machine manufactured in Japan to quantitate in percentage the amount of HbA1c in the blood specimen. Me as a lab technician,I am required to load the blood specimen manually. However before loading the blood specimen, I am instructed to shake and mix well every blood specimen and it is important to remove any air bubbles present using a disposalable plastic pipette. This is becase the machine has a laser to detect the level of blood in the tube,it will not go all the way to the bottom to aspirate blood. Thus presence of air bubbles will give false level of blood detection, causing inaccurate amount of blood aspirated, in the end causing false results.
The principle of my company’s machines is as follows; the concentration of HbA1c and the concentration of total haemoglobin in the blood sample are measured separately, and then the ratio is reported as percentage of HbA1c. A latex agglutination inhibition method is used for measurement of specific HbA1c. The total haemoglobin is then measured using the toral haemoglobin reagent where all derivatives are converted into alkaline hematin in an alkaline solution of a non-ionic detergent.
By Ivan Ng
4 July 2008 (Friday)