Diagnostics
Blood Group Typing
What is blood group typing?
Blood group typing is a simple blood test to determine an individual’s blood group. This information is essential for safe blood donation or receiving a blood transfusion. Additionally, blood typing helps identify the presence of the Rh factor, a specific substance found on the surface of red blood cells.
Who does blood group typing?
Blood tests, including blood typing, are typically conducted by medical professionals such as doctors, nurses, or trained laboratory technicians in healthcare settings like clinics, hospitals, and laboratories.
Venous (plasma) blood glucose test: A phlebotomist (A trained medical professional who draws blood from an individual’s body) or a laboratory technician collects a blood sample from a vein through venipuncture, usually from the arm. The blood sample is sent to a laboratory for analysis, and results are available within a few days.
These glucose tests are generally included in a comprehensive blood panel where blood is drawn through veins and tested. These include,
- Fasting Blood Sugar (FBS): A fasting blood sugar test is conducted after a period of overnight fasting. A normal fasting blood sugar level is 99 mg/dL or lower. A reading between 100 and 125 mg/dL indicates the presence of prediabetes, while a measurement of 126 mg/dL or higher indicates the presence of diabetes.
- Post Prandial Blood Sugar (PPBS): Postprandial means the period after a meal. The postprandial blood glucose test is performed two hours after having food to see the body’s response to a glucose post-meal. This particular test is conducted to observe how the body reacts to sugar and starch intake following a meal.
- HbA1c: The HbA1c test evaluates the average blood sugar level over a period of approximately 2 to 3 months. A normal reading is below 5.7%. If the HbA1C falls between 5.7% and 6.4%, it indicates the presence of prediabetes. An HbA1C measurement of 6.5% or higher is indicative of diabetes.
Certain glucose blood tests involve consuming a sugary liquid and waiting for a designated period before obtaining a blood sample:
- Glucose challenge test: This test is performed during pregnancy to screen for gestational diabetes. Screening means it detects an increased probability of gestational diabetes. Participants will be required to consume a sugary solution, followed by a one-hour waiting period before undergoing a blood glucose test. If it is higher than normal, an oral glucose tolerance test (OGTT) will be required for a definitive diagnosis.
- Oral glucose tolerance test (OGTT): This test is used to diagnose gestational diabetes, as well as type 2 diabetes and prediabetes in non-pregnant individuals. Before consuming a sugary drink, a baseline blood sample will be taken. Subsequent blood samples will be collected at hourly intervals over the following 2 or 3 hours to monitor changes in blood glucose levels.
What are blood types?
Blood types are determined by the presence or absence of certain proteins, known as antigens, on the surface of red blood cells. The most common blood typing system is the ABO system, which categorizes blood into four major types:
Type A: This blood type has A antigens on the red blood cells and B antibodies in the plasma.
Type B: This blood type has B antigens on the red blood cells and A antibodies in the plasma.
Type AB: This blood type has both A and B antigens on the red blood cells but no A or B antibodies in the plasma.
Type O: This blood type has no A or B antigens on the red blood cells but both A and B antibodies in the plasma.
The specific blood type is determined by the combination of antigens inherited from the parents. Understanding an individual’s blood type is important for transfusions, as receiving incompatible blood can lead to adverse reactions.
The Rh factor further classifies blood types
- Rh positive (+): People with Rh-positive blood have Rh antigens on the surface of their red blood cells.
- Rh negative (-): People with Rh-negative blood don’t have Rh antigens.
The combination of the ABO and Rh grouping systems determines the complete blood type. There are eight commonly recognized blood types:
- A positive (A+)
- A negative (A-)
- B positive (B+)
- B negative (B-)
- AB positive (AB+)
- AB negative (AB-)
- O positive (O+)
- O negative (O-)
How is the test performed?
The blood group test, also known as blood typing, is conducted through a simple laboratory procedure. The steps involved in conducting a blood group test are as follows:
Blood sample collection: A small sample of blood is collected by a laboratory technician from a vein in the arm using a needle and syringe. The area of the skin where the needle will be inserted is cleaned with an antiseptic to minimize the risk of infection.
Mixing blood with antibodies: The collected blood sample is then mixed with specific antibodies that can detect the presence of antigens on the surface of red blood cells. The antibodies used are anti-A and anti-B antibodies.
The sample is observed for any reactions between the antibodies and the antigens present on the red blood cells. If clumping occurs when anti-A antibodies are added, it indicates the presence of A antigens on the red blood cells (blood group A). Similarly, if clumping occurs with anti-B antibodies, it indicates the presence of B antigens (blood group B). If neither antibody causes clumping, it suggests blood type O, which has neither A nor B antigens.
Rh factor testing: In addition to ABO blood typing, the Rh factor is often determined. This involves testing for the presence or absence of the Rh antigen on the red blood cells. If clumping occurs, it indicates Rh-positive blood, while no clumping suggests Rh-negative blood.
The results of the blood group test determine blood type, which can be classified as A, B, AB, or O, and whether an individual is Rh-positive or Rh-negative.
Why is blood typing performed?
Blood typing is a procedure performed prior to blood transfusions or blood donation. It ensures that the recipient receives compatible blood, minimizing the risk of complications during surgery or after an injury. Receiving incompatible blood can result in a dangerous reaction called blood clumping or agglutination, which can have life-threatening consequences.
Blood typing is particularly crucial in pregnant women. The child is likely to be Rh-positive if the mother is Rh-negative and the father is Rh-positive. In such cases, the mother may need to receive a medication known as RhoGAM. This medication prevents the mother’s body from producing antibodies that could attack the baby’s blood cells and destroy them. When red blood cells are broken down, they make bilirubin. This causes an infant to become yellow (jaundice). The bilirubin level in the infant’s blood may range from mild to dangerously high.
References
- Cleveland Clinic. Rh Factor. Available from: https://my.clevelandclinic.org/health/diseases/21053-rh-factor
- Cleveland Clinic. Blood Types. Available from: https://my.clevelandclinic.org/health/articles/21213-blood-types
- Rh incompatibility. Available from: https://medlineplus.gov/ency/article/003345.htm
- Blood Typing: Purpose, Procedure, and Results. Available from: https://www.healthline.com/health/blood-typing
