diagnosis & testing

what is diagnosis????
       
it is a process of attempting to determine or identify the possible disease or disorder .
      

DIAGNOSIS OF AIDS                                                                         
HIV Testing
 
to diagnose AIDS ,The doctor will need
  • a confirmed HIV  positive test.
  • evidence of an AIDS-defining condition or severely depleted CD4 cells.
testing for HIV is a two step process, first is an  inexpensive screening is done , if the result is positive a second test i.e western blot  is done to confirm the results
Antibody tests are the most common initial screening test used.
test which include for diagnosing HIV are :

  • ELISA Test
                                      which stands for enzyme-linked immunosorbent assay, is used to detect HIV infection. If an ELISA test is positive, the Western blot test is usually administered to confirm the diagnosis. If an ELISA test is negative, but you think you may have HIV, you should be tested again in one to three months.

ELISA is quite sensitive in chronic HIV infection, but because antibodies aren't produced immediately upon infection, you may test negative during a window of a few weeks to a few months after being infected. Even though your test result may be negative during this window, you may have a high level of the virus and be at risk of transmitting infection.

  • home test
                                    The only home test approved by the FDA  is called the Home Access Express Test, which is sold in pharmacies.
  • saliva test 
                                   A cotton pad is used to obtain saliva from the inside of your cheek. The pad is placed in a vial and submitted to a laboratory for testing. Results are available in three days. Positive results should be confirmed with a blood test.

  • viral load test 
                                  This test measures the amount of HIV in your blood. Generally, it's used to monitor treatment progress or detect early HIV infection. Three technologies measure HIV viral load in the blood — reverse transcription polymerase chain reaction (RT-PCR), branched DNA (bDNA) and nucleic acid sequence-based amplification assay (NASBA). The basic principles of these tests are similar. HIV is detected using DNA sequences that bind specifically to those in the virus. It is important to note that results may vary between tests.

  • western blot
                                     This is a very sensitive blood test used to confirm a positive ELISA test result.

HOW THE TEST IS DONE???
  • blood is drawn for an enzyme immunoassay (EIA).
  • Other tests can detect antibodies in body fluids other than blood such as saliva, urine, and vaginal secretions. Some of these are designed to be rapid tests that produce results in approximately 20 minutes. These tests have accuracy rates similar to traditional blood tests.
  • HIV home-testing kits are available at many local drug stores. Blood is obtained by a finger prick and blotted on a filter strip. Other test kits use saliva or urine. The filter strip is mailed in a protective envelope to a laboratory to be tested. Results are returned by mail in one to two weeks.
  • All positive antibody screening tests must be confirmed with a follow-up blood test called the Western blot to make a positive diagnosis. If the antibody test and the Western blot are both positive, the likelihood of a person being HIV infected is >99%. Sometimes, the Western blot is "indeterminate," meaning that it is neither positive nor negative. In these cases, the tests are usually repeated at a later date. In addition, an RNA test for the virus might be done.

HIV TESTING IN INFANTS :-

CDC recommends that all pregnant women get tested for HIV before and/or during delivery. Knowing the HIV status of the mother allows physicians to prevent mother-to-child HIV transmission by providing antiretroviral treatment to both mothers infected with HIV and their newborn infants. However, it is difficult to determine if a baby born to a mother infected with HIV is actually infected because babies carry their mothers’ HIV antibodies for several months. Today, healthcare providers can conduct an HIV test for infants between ages 3 months and 15 months. Researchers are now evaluating several blood tests to determine which ones are suitable for testing babies younger than 3 months.



REFERENCE:-


http://www.ucsfhealth.org/conditions/aids/diagnosis.html

http://health.nytimes.com/health/guides/disease/aids/overview.html

http://www.emedicinehealth.com/hivaids/page5_em.htm#hivaids_diagnosis

http://www.medicinenet.com/acquired_immunodeficiency_syndrome_aids/page5.htm

http://www.niaid.nih.gov/topics/hivaids/understanding/Pages/diagnosis.aspx