Western Blot
- Sample Type
- Serum
- Fasting
- No
- Unit
- Qualitative
Function
The Western Blot is a highly specific confirmatory test used to detect specific proteins (antigens) or antibodies in a blood sample. It works by separating proteins by size via electrophoresis and then using labeled antibodies to bind to specific target bands. Historically, it has been the definitive 'second-step' test to confirm results from a screening ELISA.
Why it is Ordered
It is primarily used as a confirmatory test following a positive screening result for HIV-1 or Lyme Disease. Because screening tests are designed to be 'highly sensitive' (prone to false positives to ensure no cases are missed), the Western Blot provides the 'specificity' needed to confirm that the infection is actually present.
Associated Conditions
- HIV-1 Infection: Confirming the presence of viral proteins like p24, gp120, and gp41.
- Lyme Disease: Confirming antibodies against Borrelia burgdorferi.
- Bovine Spongiform Encephalopathy: In veterinary or specialized research contexts.
- Autoimmune Disorders: Sometimes used in research for specific protein identification.
Why Context Matters
The Western Blot is subject to human interpretation and 'indeterminate' results. If a person is in the 'window period' (very early infection), the blot may be negative or indeterminate because the body hasn't produced enough specific antibodies yet. Newer '4th Generation' assays are often replacing the Western Blot in standard HIV algorithms because they detect the virus earlier.
Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.
Clinical References
Source-of-truth databases and clinical guidelines for Western Blot:
Official Sources
- Lyme Disease Tests: MedlinePlus Medical TestMedlinePlus
Research & Guidelines
- PubMed: Western Blot Clinical GuidelinesNCBI / PubMed
Related Indicators
Medically Reviewed by Dr. Binoy Babu, MBBS
Board Certified Doctor • 10+ Years Clinical Experience
Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.
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