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Louisiana Department of Health & Hospitals | Kathy Kliebert, Secretary

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Human Immunodeficiency Virus HIV-1 Western Blot

HIV-1 Western Blot

  • Laboratory Location – Central Laboratory
  • CPT Code – 86689
  • Synonyms – HIV, Serum Western Blot
  • Test Description - The HIV-1 Western Blot is used to detect virus specific antibodies to HIV-1 in human serum or plasm. It is intended for use as an additional, more specific test for specimens that are used as an aid in the diagnosis of infection with HIV-1 and/or HIV-2. The HIV-1 Western Blot assay is a reflex test that is performed when the HIV-1/2 Plus O EIA is repeatedly reactive.

Possible Results

  • Negative = no band present
  • Positive = at least 2 of the major bands (gp160 and/or gp120, gp41, or p24) must be present
  • Indeterminate = one or more bands are present but does not meet the criteria for a positive result

Reference Range

  • Negative

Specimen Requirements

  • Specimen Type - Serum
  • Specimen Container(s) - red top tubes, Marble top tubes, polypropylene vials
  • Minumum accepted volume - 1 mL

Specimen Collection Instructions

Blood should be collected in a plastic, sterile STD Program approved collection tube. Please follow the manufacturer's instructions on clot time and centrifuge speed/time requirements.

The HIV Laboratory Test Requisition form must be filled out completely. The following information must be included on the form:

  • Patient's Name
  • Patient's Date of Birth
  • Patient's Gender
  • Patient's race/ethnicity
  • Date and time of specimen collection
  • Test requested
  • Type of specimen collected
  • Submitter's name and address
  • External ID#

Storage and Transport Instructions

Speciments should be shipped refrigerated (2-8ºC) or ambient (8-37°C).. Specimens can be stored for up to 7 days. For longer storage, specimens must be frozen at -20ºC or colder. Frozen specimens must be shipped on dry ice and received at a temperature of -20ºC or colder.

Causes for Rejection

  • Improper labeling
  • expired collection tubes
  • unspun samples
  • tubes that contain less than 90% of the total drawing capacity (QNS)
  • Specimen age greater than 7 days if specimen has not been frozen at -20ºC or colder
  • Improper storage or improper temperature requirements are also reasons for rejection

Limitations for the Procedure

Testing alone cannot be used to diagnose AIDS, which is a clinical syndrome. The diagnosis of AIDS must be establised clinically. Indeterminate immunoblots should not be used as the sole basis of HIV-1 infection. Persons with an indeterminate immunoblot should be retested using a fresh specimen after 6 months. A negative immunoblot does not exclude the possibility of exposure to or infection with HIV-1. A person who has antibodies to HIV-1 is presumed to be infected with the virus, except that a person who has participated in an HIV vaccine study may develop antibodies to the vaccine and may or may not be infected with HIV. Clinical correlation is indicated with appropriate counseling, medical evaluation and possibly additional testing to decide whether a diagnosis of HIV infection is accurate.

Interfering Substances

  • No clinically significant effect has been detected in assay results of serum or plasma samples with increased levels of protein, lipids, bilirubin, or hemolysis, or after heat inactivation of patient samples.

References

  • BioRad Genetic Systems™ HIV-1/HIV-2 Plus O EIA package insert
  • BioRad Genetic Systems™ HIV-1 Western Blot package insert

 

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