Serology

The serology laboratory specializes in detecting and measuring specific antibodies that develop in blood during a response to exposure to a disease-producing antigen. There are several techniques utilized in clinical immunologic and serologic assays. These included precipitation, immunoelectrophoresis, agglutination, complement fixation, cytolysis, neutralization, flocculation, immunodiffusion, enzyme immunooassays, enzyme-linked immunabsorbent assays (ELISA), and fluorescent antibody (FA) methods. Determinations of blood groups and Rh factors for persons donating or receiving blood utilize serologic methods. (See Blood Bank page). Your physician will frequently use the serology lab to help diagnosis such disease states as mononucleosis, syphilis, Strep infections, Herpes infections, Lupus, thyroid disorders, rheumatoid arthritis and rubella, and to establish such conditions as pregnancy.

Crestwood Medical Center is proud to offer to the online community a database of tests performed by the serology laboratory. In order to access this information simply click on the tests below that you would like to learn more about. Please bookmark our page for easier access.

Pregnancy Test (Human Chorionic Gonadotropin Test)

Immunologic tests are done frequently in the laboratory to detect pregnancy in the early stages. Lab tests for prenancy are based on the fact that during pregnancy, the placenta produces a hormone called chrorionicgonadotropin. This hormone rapidly disappears after delivery. Since HCG is present in the serum and urine of pregnant women, it is an excellent marker for confirming pregnancy. Human chorionic gonadotrophin levels of 25mIU/ml have been observed as early as 10-12 days after conception and may be detected before a first missed menses.

Rheumatoid Factor

The identification of rheumatoid factor (RF) in the serum of patients with clinical features of rheumatoid arthritis (RA) assists in confirming the diagnosis. The tests for RF are based on the reaction between antibodies in the patient's serum and an antigen used in the test. RF is present in the serum of approximately 70% to 80% of patients with rheumatoid arthritis, The highest titers are often found in severe cases of rheumatoid arthritis. Rheumatoid arthritis is an inflammatory and degenerative condition involving multiple organ systems, especially the connective tissue structures and synovial joints. This condition is characterized by an inflammatory reaction in the synovial membrane, resulting in swelling and pain in the joints. Although a specific cure is not known, appropriate therapeutic measures can suppress the inflammatory manifestations and aid in minimizing musculoskeletal dysfunction.

Rubella Titer

Rubella in a qualitative sense, the presence of rubella antibodies is an indication of previous infection and presumptive immunity. An interpretation of the test results can be used to evaluate the immune status of the individual with regard to resistance or susceptibility to primary rubella infection.

The following general vaccination guidelines have been issued by medical authorities:

• Children should receive a routine first measles vaccination at about 15 months of age.
• Children should have a second measles vaccination:
  a. upon entry to kindergarten or first grade, or
  b. upon entry to middle school or junior high school. State regulations may vary.

HIV

HIV, HUMAN IMMUNODEFICIENCY VIRUS, is a retrovirus, the agent that causes AIDS, ACQUIRED IMMUNE DEFICIENCY SYNDROME. An infected person gradually loses his immune function and becomes susceptible to numerous infections that may lead to AIDS. HIV retrovirus was discovered with AIDS in the mid 1980's. Retroviruses have a long incubation period before active disease processes begin. They infect essential bodily functions: blood cells, the nervous system, and they suppress the immune system. They replicate through a process known as reverse transcription. This is done by using the enzyme reverse transcriptase, which is carried by the retroviruses. They must convert their genomic RNA into DNA.

The structure of HIV consists of a nucleoid core with surrounding protein matrix. Both are enclosed in a lipid envelope. The nucleoid core contains the genetic material for replication. There are two proteins that enable HIV to fuse and bind with a target host: the envelope glycoprotein gpl20 and the transmembrane glycoprotein gp41. These contain two viral strands of RNA (the genetic material of HIV) and the associated reverse transcriptase enzyme.

HIV infects cells that have CD4 molecules on their outer membranes. CD4 T­lymphocytes (one type of white blood cell) are examples. HIV uses CD4 (a normal immune protein) as a receptor to attach itself. The virus can fuse with the cell wall by specifically recognizing and binding to CD4 with the viral gpl20. This fusion causes the nucleoid to enter the cell. In turn, reverse transcription then occurs, and the two strand of viral genomic RNA are changed into double­stranded DNA. This is carried to the cell nucleus and inserted with the normal DNA. Using the technology of its new host, the integrated viral DNA is transcribed to make messenger RNA (mRNA) and new strands of viral genomic RNA.

The viral mRNA is made into new viral proteins, and new virus particles are also created within the cell. The new HIV particles begin budding, which releases them from the cell surface. They also take along a piece of the cell membrane as their new envelope.

CD4 T­lymphocytes can be killed by HIV replication. By losing these cells, the nervous system becomes paralyzed. This is one mechanism that enables HIV to cause AIDS. During the earliest stages of infection, some people have symptoms of a nonspecific viral illness. The patient may be asymptomatic even though he has high antibody titers. At this phase, antigen is usually detectable in the serum. but viral cultures of patient lymphocytes may indicate the presence of the virus. As the infection grows, changes in the ratio of T4 (helper­inducer) to T8 (suppressor) cells will be noted. When the normal ratio of 2 begins to decrease, antigen may appear in the serum.

Depending on unknown and host factors, the types of symptoms and time before severe illness is variable. Terminally ill patients' antibody to the core may fall for unknown periods of time.

People should not fear giving blood. The virus cannot be transmitted this way. Some routes of transmission include unprotected sex, IV drug use and use of shared needles, history of sexually transmitted diseases, a blood transfusion between 1978 and 1985, and infected mother to baby. This is only a list of some of the transmission routes.

Since 1985, careful screening and laboratory testing of all blood donations has greatly reduced the possibility of infection from blood products. Potential at­risk donors are asked not to donate blood. All blood that tests positive for the HIV infection is discarded. At present, in the United States, there is only a small chance of HIV infection through a blood transfusion.

The only way to detect the HIV virus is with a blood test. Depending on the situation, their are two types of tests. The ELISA, also called EIA, stands for ENZYME­LINKED IMMUNOSORBENT ASSAY. This is the test you usually hear about. This is the test used when you donate blood. Today's test looks for the presence of antibodies that might occur to fight the AIDS virus if it is present in your system. It does not test for the virus itself. A positive ELISA does not always mean that you are infected with AIDS. It does mean that further testing is needed. There are two tests to use if you have a positive ELISA test. One is the WESTERN BLOT TEST. The other is called IFA. Either of these tests is used to confirm a positive ELISA test.

A negative test is not conclusive. If you suspect a recent infection, the negative test may mean that your body has not had time to develop antibodies against the AIDS virus.

Once infected, you will probably always be infected, for life. It sometimes takes years before your body begins showing the symptoms of AIDS. If you are worried, have the test! It can be done confidentially so no one will know your identity. It could stop at lot of worry on your part, The test often is available free or at low cost. Counseling is usually recommended both before and after the test. Before, to understand the test and your risk for infection. After, to understand your tests results and how to protect yourself and others. The test results are usually available within two weeks. The results are given in a confidential manner

ALABAMA AIDS HOTLINE (8:30­5:00,M­F)

1­800­228­0469

or

NATIONAL AIDS HOTLINE

1­800­342­AIDS

(24 hours a day)