HIV

CDC Recommended Laboratory HIV Testing Algorithm

Incubation period Acute Phase Asymptomatic Phase Symptomatic Phase
Description 2 – 4 weeks "flu-like" symptoms
  • progressive depletion of CD4+ T-cells
  • can last >10 years
  • AIDS develops
  • Common symptoms: chills, fever, sweats, swollen lymph glands, weakness, and weight loss
CD4+ T-cells normal low declining low to depleted
p24 antigen rising high - high
anti-HIV - rising high high
HIV RNA rising high fluctuating high
Contagious - highly moderately highly

Adapted from:

  1. Fiebig EW, et al. Dynamics of HIV viremia and antibody seroconversion in plasma donors: implications for diagnosis and staging of primary HIV infection. AIDS. 2003;17:1871-9.
  2. Cohen MS, et al. Acute HIV-1 Infection. N Engl J Med. 2011;364:1943-54.
  3. De Jong MD, et al. Clinical, virological and immunological features of primary HIV-1 infection. Genitourin Med. 1991;67:367-73.
Product Description Tests Product page
Elecsys® HIV combi PT a) Electrochemiluminescence immunoassay (ECLIA) for the qualitative detection of HIV-1 p24 antigen and antibodies to HIV-1 and HIV-2 in human serum and plasma 100
200
Elecsys® HIV Duo b) Electrochemiluminescence immunoassay (ECLIA) for the qualitative detection of HIV-1 p24 antigen and antibodies to HIV-1 and HIV-2 in human serum and plasma 300
cobas® HIV-1 c) Nucleic acid amplification test for the quantitation of human immunodeficiency virus type 1 (HIV-1) in EDTA plasma or from a cobas® Plasma Separation Card (PSC) dried plasma spot of HIV-1-infected individuals 96
cobas® HIV-1 d) 192
cobas® HIV-1 e) Nucleic acid amplification test for the quantitation of human immunodeficiency virus type 1 (HIV-1) in EDTA plasma of HIV-1-infected individuals 120
cobas® HIV-1/HIV-2 Qualitative Test d) Nucleic acid amplification test for the qualitative detection and differentiation of HIV-1 and HIV-2 in human serum, plasma, and dried blood spots (DBS). 120

a) for use on the cobas® e 411 analyzer and the cobas® e 601 / 602 modules
b) for use on the cobas® e 402 and cobas® e 801 analytical units
c) for use on the cobas® 6800/8800 Systems
d) for use on the cobas® 5800/6800/8800 Systems
e) for use on the cobas® 4800 System

Adapted from:

  1. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention (CDC). Laboratory Testing for the Diagnosis of HIV Infection: Updated Recommendations. [Internet; updated 2014 Jun 27; cited 2023 Nov]. Available from: http://dx.doi.org/10.15620/cdc.23447.
  2. Alexander TS. Human Immunodeficiency Virus Diagnostic Testing: 30 Years of Evolution. Clin Vaccine Immunol. 2016;23:249-253.
  3. European Centre for Disease Prevention and Control (ECDC). HIV testing in Europe. Evaluation of the impact of the ECDC guidance on HIV testing: increasing uptake and effectiveness in the European Union. [Internet; updated 2016; cited 2023 Nov]. Available from: https://op.europa.eu/en/publication-detail/-/publication/b6a6d67a-d896-11e6-ad7c-01aa75ed71a1/language-en.
  4. Rijksinstituut voor Volksgezondheid and Milieu (National Institute for Health and Environment of the Netherlands). Draaiboek voor Centra Seksuele Gezondheid in de Publieke Gezondheidszorg (Script for Sexual Health Centers in Public Healthcare). [Internet; updated 2024 Feb 26; cited 2024 Mar 4]. Available from: https://lci.rivm.nl/draaiboeken/consult-seksuele-gezondheid.
  5. Haute Autorité de Santé (HAS). Dépistage de l’infection par le VIH en France - Stratégies et dispositif de dépistage (Screening for HIV infection in France - Screening strategies and facilities. [Internet; updated 2009 Oct; cited 2024 Mar 4]. Available from: https://sante.gouv.fr/IMG/pdf/argumentaire_depistage_vih_HAS_2009-2.pdf.
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Step 1

Perform HIV-1/2 antigen/antibody
combination immunoassay

HIV-1/2 antigen/antibodies
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Step 2

Perform HIV-1/2 antibody differentiation test

HIV-1 antibodies
HIV-2 antibodies
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Step 3

Perform HIV-1 RNA test

HIV-1 RNA
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Summary

No laboratory evidence of HIV infection

​​​​​​​In case the clinical background indicates an acute HIV infection, repeat the HIV-1/2 Ag/Ab combination test after 1-2 weeks. If this result is again negative there is no laboratory evidence of HIV infection.
​​​​​
In case the clinical background does not indicate an acute HIV infection, but there might be a risk of infection, repeat the HIV-1/2 Ag/Ab combination test after 3-4 weeks and 3 months (because of the window phase).

If acute HIV infection is suspected, consider testing for HIV-1 RNA.

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Summary

HIV-1 antibodies detected

​​​​​​​Laboratory evidence consistent with the presence of an established HIV-1 infection.

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Summary

HIV-2 antibodies detected

Laboratory evidence consistent with the presence of HIV-2 infection.

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Summary

HIV antibodies detected

​​​​​​​Laboratory evidence consistent with the presence of HIV infection.

HIV antibodies could not be differentiated as HIV-1 or HIV-2. Additional testing for HIV-1 RNA of HIV-2 RNA should be performed if clinically indicated.

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Summary

Acute phase HIV-1 infection
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Laboratory evidence consistent with the presence of an acute HIV-1 infection.

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Summary

Initial reactive screening result not confirmed​​​​​​​

A negative HIV-1 RNA result and non-reactive or indeterminate HIV-1/HIV-2 antibody differentiation immunoassay result indicate a false-positive result on the initial immunoassay.

Follow-up testing for HIV-2 should be performed if clinically indicated. Alternatively, repeat the complete testing algorithm 2 to 4 weeks later, starting with an antigen/antibody immunoassay.

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Next Restart simulation
Step
Result
Interpretation
1
HIV-1/2 Ag/Ab test = ...
waiting for input
1
HIV-1/2 Ag/Ab test = negative

No laboratory evidence of HIV infection.

1
HIV-1/2 Ag/Ab test = positive

Possible HIV infection

Perform HIV-1/2 antibody differentiation test.

Specimens with a reactive antigen/antibody combination assay result (or repeatedly reactive, if repeat testing is recommended by the manufacturer or required by regulatory authorities) should be tested with an FDA-approved antibody assay that differentiates HIV-1 antibodies from HIV-2 antibodies. Reactive results on the initial antigen/antibody combination assay and the HIV-1/HIV-2 antibody differentiation assay should be interpreted as positive for HIV-1 antibodies, HIV-2 antibodies, or HIV antibodies, undifferentiated.

2
HIV-1 antibodies = ...
HIV-2 antibodies = ...
waiting for input
2
HIV-1 antibodies = negative
HIV-2 antibodies = negative

Inconclusive

Specimens that are reactive on the initial antigen/antibody immunoassay and non-reactive or indeterminate on the HIV-1/ HIV-2 antibody differentiation immunoassay should be tested for HIV-1 RNA.

2
HIV-1 antibodies = negative
HIV-2 antibodies = positive

Positive for HIV-2 antibodies

2
HIV-1 antibodies = positive
HIV-2 antibodies = negative

Positive for HIV-1 antibodies: Laboratory evidence consistent with presence of an established HIV-1 infection.

2
HIV-1 antibodies = positive
HIV-2 antibodies = positive

Positive for HIV antibodies: Laboratory evidence consistent with presence of HIV infection.

HIV antibodies could not be differentiated as HIV-1 or HIV-2. Additional testing for HIV-1 RNA of HIV-2 RNA should be performed if clinically indicated.

3
HIV-1 RNA test = ...
waiting for input
3
HIV-1 RNA test = negative

Initial reactive screening result not confirmed​​​​​​​

3
HIV-1 RNA test = positive

Positive for HIV-1 RNA​​​​​​​​​​​​​​

End of test sequence