Diagnosing immune disorders and allergies

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There are many tests available to diagnosis problems with the body's immune system. Different tests are used to diagnosis different types of disorders, including autoimmune disorders, allergies, genetic disorders, and antibody deficiencies.
Autoimmune disorders occur when the immune system mistakes body cells for harmful invaders, such as bacteria, and attacks them. Autoimmune disorders can destroy body tissues, cause abnormal organ growth, and/or impair organ function.
An allergy, also called a hypersensitivity reaction, occurs when the immune system overreacts to a substance (allergen) that is normally harmless. Examples of allergens include mold, pollen, animal dander, and dust mites. When a person has allergies, the white blood cells produce an antibody called immunoglobulin E (IgE) in response to one or more allergens. This antibody attaches to the allergen, triggering other immune cells to release chemicals that cause allergic symptoms, such as runny nose, watery eyes, and hives.
Some immune disorders are genetic, which means that they are passed down from parents to their children. Patients who have genetic immune disorders are born with weakened immune systems.
Some immune disorders occur when the body does not produce enough immunoglobulin antibodies. Examples of antibody deficiencies include common variable immunodeficiency (CVID), transient hypogammaglobulinemia of infancy, and X-linked hypogammaglobulinemia. These antibodies are important because they detect and bind to foreign substances (such as bacteria and viruses) that enter the body. This immune response is an important mechanism for fighting against infections. Once the antibodies attach to the foreign substances, other immune system cells are triggered to destroy the invaders. When an individual has deficient levels of immunoglobulin, he/she has a weakened immune system and an increased risk of developing infections.

synonyms

Allergen, allergen-specific immunoglobulin E (IgE) test, allergic, allergic reaction, allergic response, allergies, allergy, amniocentesis, antibodies, antibody, applied kinesiology, autoimmune disease, autoimmune disorder, autoimmunity, chorionic villus sampling, C-reactive protein test, CRP, cytogenetic analysis, DNA analysis, ELISA, enzyme-linked immunosorbent assay, erythrocyte sedimentation rate, ESR, Ig, IgE, immune, immune defense system, immune reaction, immune response, immune system, immunoglobulin, immunoglobulin E, nephelometry, prenatal test, prenatal testing, primary immune deficiency, radioallergosorbent test, RAST, secondary immune deficiency, skin test.

autoimmune disorder tests

General: Autoimmune disorders can be difficult to diagnose because signs and symptoms vary widely, depending on the specific disease. A fluorescent antinuclear antibody (FANA) test is the standard diagnostic test for autoimmune disorders. However, this test does not diagnose specific autoimmune conditions. After a patient has a positive FANA test result, additional tests may be necessary to diagnose the specific type of disorder. In some cases, such as lupus, a diagnosis can be made after the patient has a positive FANA test and experiences symptoms characteristic of the disorder.
Since autoimmune disorders can potentially lead to organ damage, patients should regularly visit their healthcare providers. Their doctors typically conduct C-reactive protein (CRP) tests and erythrocyte sedimentation rate (ESR) tests to monitor autoimmune disorders.
Fluorescent antinuclear antibody test (FANA): The fluorescent antinuclear antibody (FANA) test is considered a reliable first step for identifying systemic lupus erythematosus and other autoimmune disorders, including scleroderma, Sjögren's syndrome, Raynaud's disease, juvenile chronic arthritis, rheumatoid arthritis, and antiphospholipid antibody syndrome. The FANA test is a blood test used to detect abnormal antibodies, called autoantibodies. The autoantibodies bind to components of and individual's own cells and cause the immune system to attack the body. If autoantibodies are present, the patient has an autoimmune disorder.
During the procedure, a small sample of blood is taken from the patient and sent to a laboratory. The scientist adds methyl alcohol to a microscope slide that contains human tissue culture cells. This makes the cells permeable before they are combined with the patient's blood.
Then the patient's blood is added to the microscope slide. Fluorescent antibodies that detect the binding of human antibodies to the cells are also added. The scientist uses a fluorescent microscope to view the staining intensity and binding pattern of the cells. If autoantibodies are detected, a positive diagnosis is made for an autoimmune disorder.
If a patient has a positive FANA result, further testing may be needed to diagnose the specific type of autoimmune disorder. In some cases, the patient's symptoms and FANA results are enough to diagnose a specific condition.
In rare occasions, the FANA test results can be positive in people who do not have autoimmune disease. This is called a false positive test result. The frequency of false-positive test results increases with age. A false negative result is also possible, but it is also uncommon.
C-reactive protein (CRP) test: The C-reactive protein (CRP) test can be used to monitor inflammation, which is associated with autoimmune disorders. A high or increasing amount of CRP in the blood suggests that the patient has an acute infection or inflammation. In a healthy person, CRP is usually less than 10 milligrams per liter of blood. Most infections and inflammations result in CRP levels higher than 100 milligrams per liter of blood.
While the test is not specific enough to diagnose a particular disease, it can suggest an autoimmune disorder and it can be used to help physicians monitor inflammation and determine if current treatments are effective.
Erythrocyte sedimentation rate (ESR): An erythrocyte sedimentation rate (ESR) test may be conducted to measure and monitor inflammation associated with autoimmune disorders. This blood test measures the rate in which red blood cells settle in unclotted blood.
During an inflammatory response, the high proportion of fibrinogen in the blood causes red blood cells to stick together. The red blood cells form stacks called rouleaux, which settle faster than normal. Elevated levels usually occur in patients who have autoimmune disorders.
Normal values for men younger than 50 years old is 15 millimeters per hour, and normal values for men older than 50 are less than 20mm/hr. The normal values for women who are less than 50 years old are less than 20mm/hr, and the normal values for women older than 50 are less than 30 millimeters per hour.
Like the C-reactive protein test, an ESR test does not suggest a specific diagnosis. However, it is useful in detecting and monitoring tissue death, rheumatologic disorders, and inflammation.

allergy tests

General: Patients with allergies often know what causes their reactions and do not require testing. However, if the cause of an allergy is unclear, the patient may undergo a skin test or allergen-specific immunoglobulin (IgE) test to confirm a diagnosis. In general, the skin test is more accurate, quicker, and less expensive than the allergen-specific IgE test.
Skin test: A skin test is used to determine whether a patient is allergic to certain allergens (substances that can trigger an allergic reaction). Common allergens include dust mites, pollen, molds, and animal dander.
During the test, the skin is exposed to allergens that may be causing symptoms. A diluted form of the allergen may be scratched onto the skin's surface, injected under the skin, or applied to a patch that is stuck onto the skin. The skin is then observed for an allergic reaction. If the allergen triggers an allergic reaction, the patient will develop reddening, swelling, or a raised, itchy red wheal (bump) that looks similar to a mosquito bite. The healthcare provider will observe and measure the size of the wheal and record the results. The larger the wheal, the more severe the allergy.
A skin test is typically conducted in a healthcare provider's office. Skin tests cause minimal, if any, discomfort. The needles used during a scratch test barely penetrate the skin's surface and will not cause bleeding.
Allergen-specific immunoglobulin (IgE) test: An allergen-specific immunoglobulin E (IgE) test, commonly referred to as radioallergosorbent test (RAST®), may also be used to determine whether the patient is allergic to certain allergens. However, this test is less accurate than a skin test. It is usually performed in patients who have coexisting severe skin diseases (such as eczema or psoriasis) that make it difficult to interpret a skin test.
During the procedure, a sample of blood is taken from the patient. The blood is then sent to a laboratory that performs specific IgE blood tests. The allergen is bound to a special paper disc, called an allergosorbent. Then the patient's blood is added. If the blood contains immunoglobulin antibodies that identify and bind to the allergen, the blood will bind to them on the disc.
Another substance is added to measure the amount of IgE in the blood. The more IgE in the blood, the more severe the allergy.
A qualified healthcare provider will interpret the results of the test. In general, the sensitivity of these tests ranges from 50-90%, with the average being about 70-75%. The patient will receive test results in about seven to 14 days.

genetic immune disorders

General: Many genetic disorders can be diagnosed after a DNA analysis. This test analyzes the patient's genetic makeup to determine whether he/she has the genetic mutation (abnormality) that is associated with the disease. For some chromosomal disorders, such as Nijmegen breakage syndrome (NBS), a cytogenetic analysis test may be performed. Chromosomes contain genetic information and mutations in certain chromosomes may lead to immune disorders. If a pregnant woman is concerned that her fetus may have a genetic immune disorder, she may undergo amniocentesis or chorionic villus sampling.
Patients who are either carriers of genetic disorders or have been diagnosed with genetic disorders may wish to receive genetic counseling. A counselor will provide information and answer questions about the risk of passing the disorder on to their children.
Cytogenetic analysis: Cytogenetic analysis is a test that is used to detect chromosomal instability, which is a characteristic of some chromosomal disorders, including Nijmegen breakage syndrome. During the procedure, a sample of the patient's blood is taken and the patient's chromosomes are stained during specific stages of replication. The sample is then observed to determine whether chromosomal abnormalities are present.
DNA analysis: A DNA analysis is used to detect genetic mutations associated with a particular disorder. During the procedure, a sample of blood is taken from the patient and analyzed at a laboratory for genetic mutations.
Prenatal testing: Pregnant mothers may have their unborn children tested for genetic disorders. In order to retrieve a sample of the fetus' cells for testing, amniocentesis or chorionic villus sampling may be performed. During amniocentesis, a long, thin needle is inserted into the pregnant woman's abdominal wall and into the uterus. A small amount of fluid is removed from the sac surrounding the fetus. During chorionic villus sampling (CVS), a small piece of tissue, called chorionic villi, is removed from the placenta. There are risks associated with these both of these procedures, including miscarriage. Patients should discuss the potential risks and benefits of these procedures with their healthcare providers.

antibody deficiencies

General: A nephelometry or enzyme-linked immunosorbent assay (ELISA) may be used to diagnose antibody deficiencies. These tests measure the amount of immunoglobulin antibodies in a patient's blood.
Nephelometry: A nephelometry blood test may be performed to diagnose certain antibody deficiencies. The test quickly and accurately measures the amount of immunoglobulin M (IgM), immunoglobulin G (IgG), and immunoglobulin A (IgA) in the patient's blood. Patients with antibody deficiencies will have reduced levels of one or more of these antibodies in their blood. During the procedure, a sample of blood is taken from the patient. A special lab chemical called anti-immunoglobulin is added to the blood sample. A medical instrument then measures the movement of particles in a substance that is caused by the interaction between immunoglobulins and anti-immunoglobulins. Healthy individuals have 45-250 milligrams of IgM per deciliter of blood, 560-1,800 milligrams of IgG per deciliter of blood, and 100-400 milligrams of IgA per deciliter of blood.
Enzyme-linked immunosorbent assay (ELISA): An enzyme-linked immunosorbent assay (ELISA) measures the level of IgG subclasses in the blood. There are four types of IgG: IgG1, IgG2, IgG3, and IgG4. In healthy individuals, 60-70% of IgG antibodies in the bloodstream are IgG1, 20-30% are IgG2, 5-8% are IgG3, and 1-3% are IgG4. Individuals who have lower levels of one or more subclasses of IgG are diagnosed with IgG subclass deficiency.