Medical Terminology: Serology Tests

1. What are Serology Tests?
The presence of foreign protein in the body from a microorganism or mismatched donated blood causes a reaction of the body’s immune system. This reaction produces antibodies that destroy the foreign protein by metabolizing it into components that can be excreted safely by the body.
Serology tests examine the patient’s blood serum for antibodies. Health care providers order serology tests for a number of purposes. These include diagnosing an infection, determining if the patient has developed immunity to specific antigens, determining a patient’s blood type, and determining if the patient has an autoimmune disorder.
An autoimmune disorder occurs when the patient’s immune system identifies the patient’s own protein as a foreign protein, resulting in the patient’s immune system creating antibodies to that protein.

2. Immunoglobulin (Ig) Tests
Immunoglobulin tests are used to screen for allergies, autoimmune disease, multiple myeloma, and macroglobulinemia cancer. They are also used to assess the strength of the immune system, the patient’s immunization, and the effectiveness of treatment for infection and bone marrow cancer. An immunoglobulin test is commonly administered as a follow-up to an abnormal result from the total blood protein or blood protein electrophoresis test.

Understanding Immunoglobulin Tests
Immunoglobulins are antibodies made by the immune system in response to microorganisms that enter the body, allergens, and abnormal cells such as cancer cells. An antibody is specific to an antigen. The immunoglobulin tests measure the level of an immunoglobulin in the patient’s blood. A low level of a specific immunoglobulin increases the risk of repeated infections from an antigen. There are five major types of immunoglobulins:
. IgA: This is found in tears and saliva and protects the ears, eyes, breathing passages, digestive tract, and vagina, which are exposed to outside antigens. It comprises 10% of immunoglobulins.
. IgG: This is found in all body fluids and defends the body against viruses and bacteria. This immunoglobulin crosses the placenta. It comprises 80% of immunoglobulins.
. IgM: This is found in blood and lymph fluid and is the first response to infection. It comprises 5% of immunoglobulins, and forms when an infection occurs for the first time.
. IgE: This is found in mucous membranes, lungs, and skin and defends against allergens. A high level of IgE immunoglobulin is common in patients who are hypoallergenic. It comprises <5% of immunoglobulins.
. IgD: This is found in abdominal and chest tissues. It comprises <5% of immunoglobulins.

3. Antinuclear Antibodies (ANA) Test
The antinuclear antibodies (ANA) test is used to screen for rheumatoid arthritis, systemic lupus erythematosus (SLE), polymyositis, and scleroderma.

Understanding the Antinuclear Antibodies Test
In autoimmune diseases, the body produces antibodies that attach and destroy the body’s own cells. The antinuclear antibody test measures the pattern and amount of these antibodies.

4. Human Immunodeficiency Virus (HIV) Tests
Human immunodeficiency virus (HIV) tests are used to assess if the patient has been infected with HIV.

Understanding Human Immunodeficiency Virus Tests
The human immunodeficiency virus infects the CD4+ white blood cells that are the body’s defense against infection. There are two types of HIV. HIV-1. is common in nearly all acquired immunodeficiency syndrome (AIDS) cases. HIV-2. is associated with West Africa. HIV causes AIDS, which is incurable. There is a period when the HIV infection is not detectable in a patient. This is called the seroconversion period, also known as the window period. The patient can spread HIV during this period. The seroconversion period can be up to 2. weeks and as long as 6. months. After the seroconversion period, the HIV test is able to detect HIV antibodies or the HIV’s RNA in the patient’s blood.
There are several HIV tests:
- Enzyme-Linked Immunosorbent Assay (ELISA): The first test administered to screen a patient. This looks for HIV antibodies in the blood. If the test result is negative, then other tests are not performed. If the test result is positive, another ELISA test is performed. Other tests are performed if there are two positive ELISA tests because the ELISA test can produce a false-positive result.
- Western Blot: This tests for HIV antibodies and is more difficult to perform than the ELISA test.
- Polymerase Chain Reaction (PCR): This looks for HIV’s RNA in the blood. Polymerase chain reaction is used to identify a very recent infection and is administered to screen blood and organs before donations and when HIV antibody tests are inconclusive. The PCR test is not performed often because of expense.
- Indirect Fluorescent Antibody (IFA): This tests for HIV antibodies and is performed secondary to two positive ELISA tests.
- Saliva Test: Tests the presence of HIV in saliva. Results must be confirmed by the Western blot test.
- Rapid Test Kits: Test results are available in a half hour. Results must be confirmed by the Western blot test.
- Home Blood Test Kits: This is available without prescription. Samples are sent through the mail to the laboratory. Results are provided over the phone using an anonymous code.
Detecting HIV in a newborn is difficult because the newborn’s blood still has HIV antibodies from either HIV-positive parent for 18. months.
Testing is performed when the patient:
- Exhibits symptoms of HIV
- Has HIV risk factors
- Is donating blood or organs
- Is pregnant. An infected mother can be treated, decreasing the likelihood that HIV will be passed to the fetus

5. CD4+ Count Test
The CD4+ count is used to assess the patient’s immune system, as well as the progress and treatment of HIV; assist in the diagnosis of AIDS; and develop a baseline CD4+ count. The baseline is then compared with values over time to identify changes in levels.

Understanding the CD4+ Count Test
Three types of leukocytes (white blood cells, WBCs) important to fighting infection are T lymphocytes, T cells, and T-helper cells. The CD4+ count test measures the level of these leukocytes to assess the patient’s immune system. Patients who have a low CD4+ count are at risk for opportunistic infections.
The CD4+ count test is used to assess the immune system of patients who have HIV. The result of the CD4+ count test and the viral load test determines when antiretroviral treatment for HIV is started. The health care provider may also order the CD4+ percentage test that determines the percentage of CD4+ cells in the total number of lymphocytes and the CD8. count test that determines the level of T-suppressor cells.

6. Viral Load Measurement Test
The viral load measurement test is used to assess the progress and treatment of HIV infection.

Understanding the Viral Load Measurement Test
HIV in a patient’s blood is determined by the presence of HIV RNA. The amount of HIV RNA indicates if the infection is decreasing, stabilized, or increasing. The viral load measurement test determines the amount of HIV RNA in the patient’s blood. A viral load measurement test is administered when the patient is diagnosed with HIV and becomes the baseline. Results of subsequent viral load measurement tests are compared with the baseline to determine the infection’s progress.
There are three types of viral load measurement tests:
. Branched DNA (bDNA) test
. Nucleic acid sequence-based amplification (NASBA) test
. Reverse-transcriptase polymerase chain reaction (RT-PCR) test
The health care provider may order the CD4+ count test along with the viral load measurement test, although the viral load measurement test is more accurate than the CD4+ count test to assess the progress of the HIV infection. The viral load measurement test is not used to diagnose HIV.
A patient diagnosed with HIV who has a negative viral load measurement test result can infect another person.

7. Rheumatoid Factor (RF) Test
The rheumatoid factor (RF) test is used to screen for rheumatoid arthritis.

Understanding the Rheumatoid Factor Test
The RF is an autoantibody that destroys the patient’s own tissues, resulting in stiffness, joint pain, and inflammation. The RF test measures the amount of the RF in the blood sample and is used to differentiate rheumatoid arthritis from other forms of arthritis. There are two types of RF tests—the agglutination test and the nephelometry test.
The RF is one of other signs and symptoms used to diagnose rheumatoid arthritis. A patient may have a high level of RF but no symptoms of rheumatoid arthritis. However, the patient is likely to develop rheumatoid arthritis in the future. A patient who has a normal level of RF and symptoms of rheumatoid arthritis will likely require a second RF test.

Basic Questions
Serology Tests

1. What is the purpose of serology tests?
Serology tests examine the patient’s blood serum for antibodies.

2. What is an antibody?
The presence of foreign protein in the body from a microorganism or mismatched donated blood causes a reaction of the body’s immune system. This reaction produces antibodies that destroy the foreign protein by metabolizing it into components that can be excreted safely by the body.

3. What is an autoimmune disorder?
An autoimmune disorder occurs when the patient’s immune system identifies the patient’s own protein as a foreign protein, resulting in the patient’s immune system creating antibodies to that protein.

4. What is the purpose of the immunoglobulin tests?
Immunoglobulin tests are used to screen for allergies, autoimmune disease, multiple myeloma, and macroglobulinemia cancer. They are also used to assess the strength of the immune system, the patient’s immunization, and the effectiveness of treatment for infection and bone marrow cancer.

5. What are immunoglobulins?
Immunoglobulins are antibodies made by the immune system in response to microorganisms that enter the body, allergens, and abnormal cells such as cancer cells.

6. What is the risk of having a low level of a specific immunoglobulin?
A low level of a specific immunoglobulin increases the risk of repeated infections from an antigen.

7. What is IgA?
IgA is an immunoglobulin found in tears and saliva that protects the ears, eyes, breathing passages, digestive tract, and vagina, which are exposed to outside antigens.

8. What immunoglobulin defends the body against viruses and bacteria?
IgG is found in all body fluids and defends the body against viruses and bacteria.

9. What immunoglobulin is the first response to infection?
IgM is found in blood and lymph fluid and is the first response to infection. It forms when an infection occurs for the first time.

10. What immunoglobulin defends against allergens?
IgE is found in mucous membranes, lungs, and skin and defends against allergens. A high level of IgE immunoglobulin is common in patients who are hyperallergenic.

11. What immunoglobulin crosses the placenta?
IgG crosses the placenta.

12. What is the purpose of the antinuclear antibodies (ANA) test?
The ANA test is used to screen for rheumatoid arthritis, systemic lupus erythematosus (SLE), polymyositis, and scleroderma.

13. What does the ANA test measure?
It measures antibodies that attach and destroy the body’s own cells.

14. What does the human immunodeficiency virus (HIV) infect?
The HIV infects the CD4+ white blood cells that are the body’s defense against infection.

15. During what period is the HIV test ineffective?
There is a period when the HIV infection is not detectable in a patient. This is called the seroconversion period, also known as the window period. The patient can spread HIV during this period. The seroconversion period can be up to 2. weeks and as long as 6. months.

16. What is enzyme-linked immunosorbent assay (ELISA) test?
The ELISA is the first test administered to screen a patient. It looks for HIV antibodies in the blood.

17. What is the polymerase chain reaction (PCR) test?
The PCR test looks for HIV’s RNA in the blood. PCR is used to identify a very recent infection and is administered to screen blood and organs before donations and when HIV antibody tests are inconclusive.

18. Why is the PCR test not performed frequently?
The PCR test is not performed often because of expense.

19. Why is the indirect fluorescent antibody (IFA) test performed?
The IFA test screens for HIV antibodies and is performed secondary to two positive ELISA tests.

20. Why is it difficult to detect HIV in a newborn?
Detecting HIV in a newborn is difficult because the newborn’s blood still has HIV antibodies from either HIV-positive parent for 18. months.

21. What does the CD4+ count test measure?
The CD4+ count test measures the level of leukocytes to assess the patient’s immune system.

22. What are the three types of leukocytes measured by the CD4+ test?
The three types of leukocytes (white blood cells, WBCs) important in fighting infection are T lymphocytes, T cells, and T-helper cells.

23. What is the purpose of the viral load measurement test?
The viral load measurement test is used to assess the progress and treatment of HIV infection by measuring the amount of HIV in the patient.

24. Why is the viral load measurement test administered when the patient is diagnosed with HIV?
A viral load measurement test is administered when the patient is diagnosed with HIV to establish the baseline.

25. What is the rheumatoid factor (RF)?
The RF is an autoantibody that destroys the patient’s own tissues, resulting in stiffness, joint pain, and inflammation.