HIV-1 Antigen and HIV-1/HIV-2 Antibody (Human Immunodeficiency Virus) with Reflex to HIV-1/HIV-2 Antibody Differentiation

Brief Description

Specimens will be screened using the (CLIA) test for the qualitative detection of HIV-1 p24 antigen and IgM and IgG antibodies to HIV-1 and/or HIV-2.

Any repeatedly reactive CLIA specimen will be tested with the Geenius assay that differentiated antibodies to Human Immunodeficiency Virus Types 1 and 2 (HIV-1/HIV-2).  If the Geenius interpretation is negative, HIV-1 indeterminate, HIV-2 indeterminate, the specimen will be reflexed to Aptima HIV-1 RNA nucleic acid amplification test (NAAT).

This multi-test algorithm is recommended by the Centers for Disease Control and Prevention (CDC Testing Laboratory HIV Testing Algorithm Guidelines) and has been adopted by the Clinical Laboratory Standards Institute (CLSI) for the diagnosis of HIV. This test is not intended for use in screening blood or plasma donors. This test has not been FDA approved for children less than 2 years of age or for cadaveric specimens.

Laboratory Unit



  • Chemiluminescent Immunoassay (CLIA)
  • HIV-1/HIV-2 Antibody differentiation assay - Geenius
  • HIV-1 RNA (Qualitative): Nucleic Acid Amplification Test (NAAT)

Specimen Collection


Collect in gold top SST tube, centrifuge at 1000-3000 (g) for 10 minutes. 

Collect in tiger top SST tube centrifuge at 1000-3000 (g) for 10 minutes. 


Serum separated from the clot or gel separator can be maintained at refrigerated temperature (2-8°C) during transit for no more than five days after collection. 

Serum separated from the clot can be aliquoted, stored frozen (-20°C or colder) and shipped with dry ice for up to 90 days.  Avoid multiple freeze thaw cycles.

Acceptable Specimen Type(s)


Test Request

Possible Results

  • HIV Ag/Ab Chemiluminescent Immunoassay (CLIA)

    • Reactive
    • Non-Reactive
    • Unsatisfactory
  • HIV-1/HIV-2 Antibody differentiation assay

    • HIV-1 Positive

    • HIV Antibody Negative

    • HIV-1 Indeterminate

    • HIV Positive Untypable (undifferentiated)

    • HIV-2 Positive

    • HIV-2 Indeterminate

    • HIV Indeterminate

    • HIV-2 Positive with HIV-1 cross reactivity

    • Unsatisfactory

  • HIV-1 RNA (Qualitative)

    • HIV-1 Detected

    • HIV-1 Not Detected

    • Unsatisfactory

Reference Range


Unacceptable Conditions

  • Received in collection outfit that is not approved for testing by the indicated method
  • Grossly hemolyzed, lipemic, turbid, or contaminated
  • Broken or leaked in transit
  • Insufficient quantity for testing
  • No identification on specimen
  • Identifying information on the tube and form do not match
  • No identification on submission form
  • Specimen received unspun
  • Specimens left at >8°C for more than 24 hours
  • Specimens not frozen within 5 days
  • Specimens not collected in SST tubes for viral load testing

Interfering Substances

Hemolysis and bacterial contamination

Result Reported

7-10 days


Download this pdf file. Fee schedule

LOINC/Order Codes

  • 56888-1 (Order code: 13700)
  • 49660-4 (Order code: 350000)
  • 5018-7 (Order code: 13590)

Additional Information

GPHL has used the American Public Health Association/Centers for Disease Control recommendation of the new 4th Generation Algorithm from the December 2012 HIV Diagnostic Conference as a reference for the new HIV algorithm. Please refer to this quick guide reference for information on testing and reporting.

Suggested Reporting Language for the HIV Laboratory Diagnostic Testing Algorithm