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What is a Western Blot test?

Western blotting is an important test used in cell and molecular biology to identify and separate specific proteins present in cells on the basis of their type and molecular weight.
Once separated, the proteins are transferred to a membrane and incubated with antibodies that are specific to the protein. As the antibodies react with proteins, various bands form on the membrane indicating the presence of specific proteins. The thickness of the band depends on the amount of protein in the sample.
Earlier this test was a complementary procedure along with enzyme-linked immunosorbent assay (ELISA) test for the detection of various microbial pathogens; however, advancements in medical technology have made it almost obsolete. The Centers for Disease Control has now recommended discontinuing this test completely.
Presently, the western blot test is not advised to confirm the results obtained after ELISA as other tests help in much faster diagnosis.

  1. Why is a Western Blot test performed?
  2. How do you prepare for a Western Blot test?
  3. How is a Western Blot test performed?
  4. What do Western Blot test results mean?

Western blot test is useful in the diagnosis of immunocompromised conditions, such as HIV, AIDS and Lyme disease. It is a common procedure recommended during pregnancy. Any person exposed to HIV needs to undergo the test. People with a high risk of exposure to HIV include the following:

  • Those indulging in unsafe sexual intercourse 
  • Individuals with an HIV positive partner
  • Those receiving blood transfusions
  • Those exposed to other sexually transmitted diseases
  • Individuals who have multiple sexual partners

No special preparations are needed for a western blot test. The method and purpose of the test will be explained to you before you undergo the test. No fasting is required for this test. However, if you feel anxious, seek support from a relative or a friend.

For a western blot, a blood sample is taken in a special collection tube using a needle and syringe. A medical technician will first examine your arm or the back of the hand to look for a suitable vein. Blood will then be collected after tying a tourniquet and cleaning the site of injection with an antiseptic solution.
The collection tube will be labelled, placed in a biohazard bag and sent to a lab for analysis. After the test, the technician will ask you to apply pressure at the site of puncture and will bandage it to stop bleeding and prevent infection.

Normal results:

If western blot test results are negative despite a positive ELISA result, then the test needs to be repeated in 3 to 6 months. In such cases, the HIV infection may be present, but may not yet be detectable. During that time, adequate protection should be taken to prevent the transmission of the virus.
If the test is negative and the person is not at risk of exposure to HIV, then no further testing is required. 

Abnormal results:

If the test is positive, it is considered an abnormal result.
A positive Western blot test confirms viral replication and the presence of HIV antibodies. It is also a confirmatory test for Lyme disease. A positive ELISA test along with abnormal western blot test confirms the diagnosis. Treatments are more effective and have fewer side effects when begun early in HIV infections. Diagnosing HIV in newborns is difficult as antibodies produced by the mother are still present in the baby for up to 18 months.

The following steps must be taken in case you get a positive result:

  • Seek medical advice immediately. Some additional tests might be needed for a complete assessment of the situation
  • A treatment plan is to be made and started, which includes the following:
    • Antiretroviral therapy
    • Information about further specialist treatment
    • Information about local support groups
    • Advice on how to prevent further transmission
  • All test reports are kept confidential and in some cases, anonymous
  • If the result turns out to be positive, it is advised that you inform your partner as well, as screening is recommended for them too
  • Financial assistance for lower-income groups is available for treating HIV infections
  • Several insurance companies and government health programs also offer help to those in need

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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  1. Mahmood T, Yang PC. Western blot: technique, theory, and trouble shooting. N Am J Med Sci. 2012 Sep;4(9):429-34. PMID: 23050259
  2. Denise. D. Wilson. McGraw-Hill Manual of Laboratory and Diagnostic Tests. 1st Edition; ISBN10: 0071481524
  3. Harvey Artsob. Western Blot as a confirmatory test for Lyme disease. Can J Infect Dis. 1993 Mar-Apr; 4(2): 115–116. PMID: 22346434
  4. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; HIV Testing
  5. Tahrin Mahmood, Ping-Chang Yang. Western Blot: Technique, Theory, and Trouble Shooting. N Am J Med Sci. 2012 Sep; 4(9): 429–434. PMID: 23050259