Human Immunodeficiency Virus - HIV

HIV type 1 (HIV-1) and type 2 (HIV-2) are the two etiologic agents of AIDS. HIV-1 is the cause of much of the AIDS pandemic around the world. HIV-2 is endemic in West Africa, but an increasing number of cases have been seen elsewhere, including the United States. Pre- and postexposure treatments have become available to avoid contracting HIV, and therapy exists to treat HIV infection. However, infection rates remain high among at-risk populations, and HIV continues to be a major public health problem. Transmission is primarily via sexual contact (particularly in men who have sex with men) or injection drug use; other modes of transmission include blood transfusion and perinatal exposure. HIV is not transmitted via saliva, insect vectors, or household contacts. Screening in asymptomatic individuals and early identification of active disease are critical. Recommended diagnostic testing includes “fourth generation tests” that detect both HIV antigens and antibodies, HIV-1/HIV-2 antibody differentiation tests, and nucleic acid amplification tests (NAATs).

Tabs Content

Clinical Overview

Quick Answers

What tests are used for HIV screening and diagnosis?

Testing for HIV involves serologic testing to detect HIV antibodies and/or antigens, and molecular testing. The antigen-antibody test (referred to as the fourth generation HIV test) is the recommended screening test for HIV and is widely available. NAAT is generally not recommended for screening, except in patients who present with symptoms of HIV infection and have known recent exposure; however, NAAT is recommended as part of the diagnostic algorithm and for monitoring of disease (see Laboratory Testing below). Point-of-care rapid tests are also available. Positive results of these tests require confirmation using additional tests.

How quickly can HIV be detected after infection?

The length of time after exposure before HIV infection can be detected (window period) depends on the type of test used. NAATs can identify HIV 10-33 days after infection, and fourth generation antigen-antibody tests are able to detect HIV 18-45 days after exposure. Antibody-only tests require additional time to yield reliable results (23-90 days after exposure), as the patient must mount an immune response to the HIV infection before antibodies can be detected.

How often should testing be performed in those at high-risk for HIV?

The CDC recommends that individuals at high risk for HIV be tested at least annually, and sexually active gay and bisexual men should consider being tested every 3-6 months. (See Indications for Testing for groups at high risk and for general testing recommendations.)

Is repeat testing recommended after a negative result?

If a rapid test result is negative in a patient with a possible exposure, testing should be repeated after the window period to confirm the negative result. For patients with a negative laboratory-performed antigen-antibody test, the CDC recommends that the test be repeated 45 days after the most recent exposure. In general, repeat testing should be considered in high-risk patients if clinically indicated.

Can pre- or postexposure prophylaxis affect test results?

There is evidence that taking pre- or postexposure prophylactic medications to mitigate HIV risk can affect the accuracy of the NAAT result.

Human Immunodeficiency Virus in Adults and Adolescents Testing Algorithm

Indications for Testing

Individuals with symptoms of infection, recent exposure to an HIV-infected person, or history of high-risk behavior should be tested, as should pregnant women and infants born to HIV-positive mothers. Groups at greatest risk for HIV include the following:

Men who have sex with men
Individuals who have sex with HIV-positive partners
Those who have had multiple sex partners since last HIV test (or partners with HIV risk factors themselves, or whose sexual history is unknown)
Intravenous drug users
Individuals with other sexually transmitted diseases

Guideline Recommendations for HIV Screening
CDC^a (endorsed by AAFP, ACOG, ACP, IDSA)	All individuals 13-64 years of age (testing recommended at least once) Patients at high risk for HIV (annual screening recommended) Pregnant women (routine prenatal screening recommended)
USPSTF^b	All individuals 15-65 years of age At-risk individuals <15 years or >65 years Pregnant women, including untested women who present in labor with unknown HIV status
^aRecommendations issued initially in 2006 and current in 2018. ^bRecommendations issued in 2013 and current in 2018. AAFP, American Academy of Family Physicians; ACOG, American College of Obstetricians and Gynecologists; ACP, American College of Physicians; IDSA, Infectious Diseases Society of America; USPSTF, U.S. Preventive Services Task Force Sources: CDC, 2018 ; USPSTF, 2013 , ACOG, 2014

Laboratory Testing

Refer to ARUP's testing algorithm:

Human Immunodeficiency Virus in Adults and Adolescents Testing algorithm

Diagnostic Tests

Screening

Rapid Screening Tests

Rapid screening diagnostic tests can be performed at the point of care and provide results within minutes. However, many such tests are antibody-only tests and are not considered reliable until 23-90 days after exposure. Some rapid antigen-antibody tests are available, but are unable to detect HIV until 18-45 days after exposure. All preliminary positive screening test results should be followed up with additional testing (please refer to the algorithm). The Determine Alere rapid screening test is a fourth generation rapid test and can be followed directly with HIV-1/HIV-2 antibody differentiation testing.

If a rapid test result is negative in a patient with a possible exposure, testing should be repeated after the window period to confirm the negative result. Repeat testing is also recommended in high-risk patients if clinically indicated.

Antigen/Antibody Tests

Combined antigen-antibody testing enables HIV to be detected sooner after exposure, reducing the diagnostic window compared with the antibody-only assay, and is less expensive than NAAT. Fourth generation antibody-antigen tests enable the diagnosis of acute HIV infection when patients are highly infectious. A limitation of these tests is that they do not distinguish between the presence of HIV-1 p24 antigen, HIV-1 antibodies, and HIV-2 antibodies. (See algorithm for best practices in terms of testing; see ARUP Lab Tests below for information about reflex tests offered by ARUP.)

In high-risk patients with negative initial antigen-antibody test results, consider repeat testing if clinically indicated. The CDC recommends that the test be repeated 45 days after the most recent exposure.

Confirmation Tests

Confirmation tests are supplemental tests indicated in patients with repeatedly reactive fourth generation antigen-antibody tests (as recommended by the CDC HIV diagnostic algorithm issued in 2014 and updated slightly in 2018). These tests may include reflex components, such as an HIV-1 quantitative NAAT. (See ARUP Lab Tests below.) Confirmation tests should not be used as rapid screening tests, nor as follow-up tests for positive rapid screening tests.

Antibody Differentiation Tests

Test that distinguish between HIV-1 and HIV-2 antibodies are preferred confirmatory tests. In patients with negative or indeterminate results for HIV-1/HIV-2 antibody differentiation, a quantitative NAAT is recommended. This multitest approach is recommended by the CDC for the diagnosis of HIV (CDC HIV diagnostic algorithm). If the antibody differentiation test yields positive results for both HIV-1 and HIV-2, HIV-1 NAAT testing is recommended to differentiate and rule out dual infection.

Western Blot Tests

Western blot is no longer recommended for confirmation testing; there is evidence that this testing method can yield false-negative or indeterminate results when used for confirmation testing early in the disease course. The CDC recommends NAAT testing be used for confirmation (CDC HIV diagnostic algorithm). Although there are certain clinical scenarios in which western blot is helpful, its use is limited.

Follow-Up Tests

Nucleic Acid Amplification Tests

Follow-up testing may consist of quantitative or qualitative NAAT to detect acute HIV infection or to identify HIV-1 RNA and DNA in infants. (Infants born to HIV-positive mothers should be tested using NAAT.) NAATs can be used to resolve discrepant results between fourth generation antigen-antibody tests and confirmatory tests such as the antibody differentiation immunoassay. NAAT can also be used to resolve indeterminate results of antibody differentiation testing. Different NAAT technologies are available (eg, transcription-mediated amplification [TMA], polymerase chain reaction [PCR]).

In infants with an initially positive test result, repeat testing is recommended as soon as possible by a test on a second specimen. In infants with perinatal exposure to HIV, testing should be performed at 14-21 days of life, 1-2 months, and again at 4-6 months of age.

Genotyping Tests

Genotyping tests are recommended for treatment-naïve patients before the initiation of antiretroviral therapy and in all patients who experience treatment failure. Refer to the Human Immunodeficiency Virus 1, Antiretroviral Drug Resistance Testing topic for information about genotyping analysis before the administration of antiretroviral drugs. For more information concerning mutations associated with viral resistance to therapy, refer to ARUP's ViroSeq HIV-1 Antiretroviral Drug Resistance Report.

Monitoring Tests

Quantitative viral load testing can be used to determine a therapeutic plan and allows for monitoring during treatment. Appropriate monitoring tests include quantitative NAAT and quantitative CD4 lymphocyte tests. Although the absolute CD4 lymphocyte count can aid in the monitoring of HIV, CD4 testing is not required for patients once viral suppression has been established (ie, is stable). The HIV Medicine Association recommends the CD4 count be monitored every 3-6 months for the first 2 years after treatment begins; after 2 years, in patients with an undetectable viral load and CD4 counts of 300-500 cells/mm³, the CD4 count should be measured annually. CD4 monitoring can be considered optional once the CD4 count is consistently >500 cells/mm³.

Drug resistance testing allows for guided therapy decisions, particularly if the patient’s response to therapy diminishes. For more information about mutations associated with viral resistance to therapy, refer to ARUP's ViroSeq HIV-1 Antiretroviral Drug Resistance Report.

ARUP Lab Tests

Fourth Generation Antigen/Antibody Tests

Human Immunodeficiency Virus (HIV) Combo Antigen/Antibody (HIV-1/O/2) by CIA, Reflexive Panel 2012674

Method: Qualitative Chemiluminescent Immunoassay/Qualitative Immunoassay/Quantitative Transcription-Mediated Amplification

Components: HIV-1 p24 antigen, antibodies to HIV-1 (groups M and O) and HIV-2

Human Immunodeficiency Virus (HIV) Combo Antigen/Antibody (HIV-1/O/2) by CIA, with Reflex to HIV-1 Antibody Confirmation by Western Blot 2006526

Method: Qualitative Chemiluminescent Immunoassay /Qualitative Western Blot

Components: HIV-1 p24 antigen, antibodies to HIV-1 (groups M and O) and HIV-2

Human Immunodeficiency Virus (HIV) Combo Antigen/Antibody (HIV-1/O/2) by CIA with Reflex to HIV-1/HIV-2 Antibody Differentiation, Supplemental 2013333

Method: Qualitative Chemiluminescent Immunoassay/Qualitative Immunoassay

Components: HIV-1 p24 antigen, antibodies to HIV-1 (groups M and O) and HIV-2

Confirmation Tests

Human Immunodeficiency Virus Types 1 and 2 (HIV-1/2) Antibody Differentiation, Supplemental, with Reflex to HIV-1 Quantitative NAAT, Plasma 2012669

Method: Qualitative Immunoassay/Quantitative Transcription-Mediated Amplification

Human Immunodeficiency Virus Types 1 and 2 (HIV-1/2) Antibody Differentiation, Supplemental 2013107

Method: Qualitative Immunoassay

Human Immunodeficiency Virus Type 1 (HIV-1) Antibody Confirmation by Western Blot 0020284

Method: Qualitative Western Blot

NAAT and PCR

Preferred test for diagnosis in infants

Human Immunodeficiency Virus 1 (HIV-1) by Qualitative PCR 0093061

Method: Qualitative Polymerase Chain Reaction

Diagnosis, monitoring

Human Immunodeficiency Virus 1 (HIV-1) by Quantitative NAAT, Plasma 3000867

Method: Quantitative Transcription-Mediated Amplification

Human Immunodeficiency Virus 1 (HIV-1) by Quantitative NAAT, CSF 3000872

Method: Quantitative Transcription-Mediated Amplification

Human Immunodeficiency Virus 1 (HIV-1) by Quantitative NAAT with Reflex to HIV-1 Genotype by Sequencing 3000870

Method: Quantitative Transcription-Mediated Amplification/Sequencing

Human Immunodeficiency Virus 1 (HIV-1) by Quantitative NAAT with Reflex to HIV PhenoSense GT 3000871

Method: Quantitative Transcription-Mediated Amplification/Sequencing/Culture

CD4 Lymphocyte Tests

Monitoring

Lymphocyte Subset Panel 1 - CD4 Absolute Count Only 0095854

Method: Quantitative Flow Cytometry

Lymphocyte Subset Panel 2 - CD4 Percent and Absolute 0095885

Method: Quantitative Flow Cytometry

Medical Experts

Hillyard, David R., MD, Medical Director, Molecular Infectious Diseases at ARUP Laboratories; Professor of Clinical Pathology, Adjunct Professor of Biology, University of Utah

Slev, Patricia R., PhD, Laboratory Section Chief, Immunology, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

References

Guidelines

Campbell-Yesufu OT, Gandhi RT. Update on human immunodeficiency virus (HIV)-2 infection. Clin Infect Dis. 2011; 52(6): 780-7. PubMed
Centers for Disease Control and Prevention. About HIV/AIDS. CDC. Atlanta, GA [Last Updated: Oct 2018; Accessed: Nov 2018]
Centers for Disease Control and Prevention. HIV/AIDS Statistics Overview. CDC. Atlanta, GA [Last Updated: Jul 2018; Accessed: Nov 2018]
Centers for Disease Control and Prevention. HIV Transmission. CDC. Atlanta, GA [Last Updated: Oct 2018; Accessed: Nov 2018]
Centers for Disease Control and Prevention. HIV/AIDS Testing. CDC. Atlanta, GA [Last updated: Oct 2018; Accessed: Nov 2018]
U.S. Preventive Services Task Force. Human Immunodeficiency Virus (HIV) Infection: Screening. USPSTF. Rockville, MD [Published: Apr 2013; Accessed: Feb 2018]
ACOG Committee Opinion no 596: Committee on Gynecologic Practice: Routine human immunodeficiency virus screening. Obstet Gynecol. 2014; 123(5): 1137-9. PubMed
Centers for Disease Control and Prevention. Technical update : Use of the Determine HIV 1/2 Ag/Ab combo test with serum or plasma in the laboratory algorithm for HIV diagnosis.. CDC. Atlanta, GA [Accessed: Nov 2018]
Cohen MS, Shaw GM, McMichael AJ, Haynes BF. Acute HIV-1 Infection. N Engl J Med. 2011; 364(20): 1943-54. PubMed
Centers for Disease Control and Prevention. 2018 Quick reference guide: Recommended laboratory HIV testing algorithm for serum or plasma specimens. CDC. Atlanta, GA [Updated: Jan 2018; Accessed: Nov 2018]
Branson B, Owen S, Wesolowski L, et al. Laboratory Testing for the Diagnosis of HIV Infection: Updated Recommendations. Centers for Disease Control and Prevention. Atlanta, GA [Published: Jun 2014; Accessed: Feb 2018]
Antiretroviral Therapy and Medical Management of Children Living with HIV Panel. Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection. Diagnosis of HIV Infection in Infants and Children. AIDSinfo, U.S. Department of Health and Human Services. Rockville, MD [Last Updated: Nov 2017; Accessed: Nov 2018]
Antiretroviral Guidelines for Adults and Adolescents Panel Members and Consultants. Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV. Laboratory Testing: Drug Resistance Testing. AIDSinfo, U.S. Department of Health and Human Services. Rockville, MD [Last Updated: Oct 2018; Accessed: Nov 2018]
HIV Medicine Association of the Infectious Diseases Society of America. HIV Medicine Association: Five Things Physicians and Patients Should Question. An initiative of the ABIM Foundation. Choosing Wisely. Philadelphia, PA [Accessed: Nov 2018]

General References

Branson B, Handsfield H, Lampe M, Janssen R, Taylor A, Lyss S, Clark J. Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings. 55(RR14);1-17. Centers for Disease Control and Prevention. Atlanta, GA [Last Reviewed: Sep 2006; Accessed: Feb 2018]

Chu C, Selwyn PA. Diagnosis and initial management of acute HIV infection. Am Fam Physician. 2010; 81(10): 1239-44. PubMed

Cornett JK, Kirn TJ. Laboratory diagnosis of HIV in adults: a review of current methods. Clin Infect Dis. 2013; 57(5): 712-8. PubMed

d'Ettorre G, Zaffiri L, Ceccarelli G, Mastroianni CM, Vullo V. The role of HIV-DNA testing in clinical practice. New Microbiol. 2010; 33(1): 1-11. PubMed

Workowski KA, Bolan GA, Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep. 2015; 64(RR-03): 1-137. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology^®

Ebbert MT, Mallory MA, Wilson AR, Dooley SK, Hillyard DR. Application of a new informatics tool for contamination screening in the HIV sequencing laboratory. J Clin Virol. 2013; 57(3): 249-53. PubMed

Lloyd IE, Clement PW, Salzman KL, Jensen RL, Salama ME, Palmer CA. An unusual and challenging case of HIV-associated primary CNS Lymphoma with Hodgkin-like morphology and HIV encephalitis. Diagn Pathol. 2015; 10: 152. PubMed

McCarthy MW, Genzen JR, Wilkin TJ, Singh HK. Use of a commercial HIV co-receptor tropism assay in clinical practice. AIDS Patient Care STDS. 2015; 29(2): 53-4. PubMed

Melis R, Lewis T, Millson A, Lyon E, McMillin GA, Slev PR, Swensen J. Copy number variation and incomplete linkage disequilibrium interfere with the HCP5 genotyping assay for abacavir hypersensitivity. Genet Test Mol Biomarkers. 2012; 16(9): 1111-4. PubMed

Pyne MT, Hackett J, Holzmayer V, Hillyard DR. Large-scale analysis of the prevalence and geographic distribution of HIV-1 non-B variants in the United States. J Clin Microbiol. 2013; 51(8): 2662-9. PubMed

Pyne MT, Wilson A, Hillyard DR. Large-scale comparison of Roche Cobas AmpliPrep/Cobas TaqMan and Abbott RealTime HIV assays. J Virol Methods. 2012; 184(1-2): 106-8. PubMed

Rossi A, Couturier MR. The Brief Case: Cryptosporidiosis in a Severely Immunocompromised HIV Patient. J Clin Microbiol. 2016; 54(9): 2219-21. PubMed

Taborda NA, Cataño JC, Delgado JC, Rugeles MT, Montoya CJ. Higher SLPI expression, lower immune activation, and increased frequency of immune cells in a cohort of Colombian HIV-1 controllers. J Acquir Immune Defic Syndr. 2012; 60(1): 12-9. PubMed

Wyness SP, Yee MA, La'ulu SL, Tosiello L, Straseski JA. Multiple macroenzymes in a patient with AIDS: diagnosis using ultrafiltration. Am J Clin Pathol. 2014; 142(2): 266-8. PubMed

Content Review:

November 2018

Last Update: November 2018


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	Human Immunodeficiency Virus - HIV. ARUP Consult^©. Retrieved November 12, 2018, from: https://arupconsult.com/content/human-immunodeficiency-virus

Human Immunodeficiency Virus - HIV

Quick Answers

What tests are used for HIV screening and diagnosis?

How quickly can HIV be detected after infection?

How often should testing be performed in those at high-risk for HIV?

Is repeat testing recommended after a negative result?

Can pre- or postexposure prophylaxis affect test results?

Human Immunodeficiency Virus in Adults and Adolescents Testing Algorithm

Indications for Testing

Laboratory Testing

Diagnostic Tests

Screening

Rapid Screening Tests

Antigen/Antibody Tests

Confirmation Tests

Antibody Differentiation Tests

Western Blot Tests

Follow-Up Tests

Nucleic Acid Amplification Tests

Genotyping Tests

Monitoring Tests

ARUP Lab Tests

Medical Experts

References

Guidelines

General References

References from the ARUP Institute for Clinical and Experimental Pathology®

References from the ARUP Institute for Clinical and Experimental Pathology^®