Blood typing and cross matching test results are determined based on the reaction between the antigens and antibodies. An antigen causes the body to launch an attack against a foreign body and is known as an immune response. The attack begins when the body builds a special protein called an antibody. This antibody is uniquely designed to attack and nullify the foreign attack. In general a person's body makes antibodies only against foreign bodies and not against its own antigens.
Among the various antigens present in a person's body, the antigens found on the surface of red blood cells are important because they determine the person's blood type. When red blood cells having a certain blood type antigen are mixed with serum containing antibodies against that particular antigen, the antibodies attack and stick to the antigen. This is seen as clumping, formation of clump of cells while testing is done in a test tube.
For typing blood, a person's blood cells and serum are mixed in a test tube along with commercially prepared serum and cells. Clumping refers to the type of antigens or antibodies present and helps in determining the person's blood type. While cross matching blood, the patient's serum is mixed with cells from donor blood that may be used for transfusion. Clumping or lack of clumping in the test tube tells whether or not the blood is compatible.
There are over 600 known red blood cell antigens that are organized into 22 blood group systems. However routine blood typing and cross matching generally involves only two systems namely:
Blood typing helps in determining the blood type a person has. ABO system is used to classify the blood type. There are four main categories under the ABO system:
Blood typing also helps in determining the Rh factor of the blood. People who have the Rh protein in their blood are termed as Rh + (positive) and ones without it are termed as Rh – (negative). The Rh type is useful in deciding the blood type a person can safely receive during transfusion.
Blood type of a person is inherited and there is no normal or abnormal type. The blood type of a person is determined by checking out the following:
Type A: If the blood cells of a person agglutinate with Type A serum then the person has A blood type.
Type B: If the blood cells of a person agglutinate with Type B serum then the person has B blood type.
Type AB: If the blood cells of a person agglutinate with Type A and Type B serum then the person has AB blood type.
Type O: If the blood cell of a person does not agglutinate with Type A or Type B serum then the person has O blood type.
Understanding back typing
People with type A blood will have anti-B antibodies. People with type B blood will have anti-A antibodies. People with type O blood will have both. So if the person's:
Blood clumps only when B cells are added then the blood type of the person is A.
Blood clumps only when A cells are added then the blood type of the person is B.
Blood clumps in both cases the blood type of the person is O.
Blood does not clump when both types of blood are added then the blood type of the person is AB.
Understanding Rh results
1. If the person's blood clumps together when anti-Rh serum is added then the person is Rh+.
2. If the person's blood does not clump together when anti-Rh serum is added then the person is Rh-.
Blood typing and cross matching results
There is no normal or abnormal result. However the result may make us understand the following:
Ferritin Blood Test
The iron storage in the body is estimated by the levels of ferritin present in the blood. Serum ferritin is a protein that carries the iron in the blood. The determination of serum ferritin estimates the amount of iron present in the body. Ferritin is found in higher concentrations in spleen, liver and bone marrow where there is a production of blood cells. The amount of ferritin found in the blood is always lesser than these organs. The predominant concentration is often found in the spleen and bone marrow.
Ferritin estimation is an important diagnostic approach in identifying conditions such as anemia, infections and inflammation. The normal reference range of ferritin is 12 - 300 ng/ml in men and 12-150 ng/ml in women. It is recommended that any values below 60 indicate iron deficiency and requires treatment. Low ferritin levels can occur due to heavy menstrual bleeding, inadequate iron in the diet, gastrointestinal bleeding, colon cancer, hemorrhoids or even psoriasis. A person suffering from an underlying condition associated with anemia experiences symptoms such as dizziness, fatigue, headaches, loss of libido, abdominal pain and also joint pains. The ferritin levels are often high in conditions such as hemochromatosis, hemolytic anemia and sideroblastic anemia. Birth control pill and anti thyroid medicines can alter blood ferritin values. Those recovering from surgery or illness are also likely to have lower values of ferritin in the blood.
Although iron supplements are recommended for pregnant women and patients having low iron concentrations, increased levels of iron may often lead to toxicity. Ferritin is stored in the body especially in organs like liver, spleen and bone marrow to enable the balance of iron composition in the body. In iron deficiency anemia, the iron stored is used in the production of blood cells leading to depletion of ferritin levels in the organs.
Syphilis Test VDRL
The syphilis test, VDRL is used to diagnose syphilis. The nontreponemal test is usually performed on blood but may be done on a serum sample or cerebro-spinal fluid (CSF). The test checks for an antibody that can be produced while infected with syphilis. Syphilis test VDRL is not very useful for detecting syphilis in very early or advanced stages. The test is also used to monitor patients' response to syphilis treatment. Syphilis VDRL test can result in false positive result even in the absence of infection due to recent immunization, other bacterial and viral infections and certain chronic conditions (e.g. liver disease, malignancy). Hence, a confirmatory test, the FTA-ABS test is done to check for syphilis-specific antibodies. Though no special preparation is required on the part of an individual who is to be tested, health care officials recommend abstaining from alcohol consumption 24 hours before a VDRL test.
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Bibliography / Reference
Collection of Pages - Last revised Date: February 9, 2023