Human Immunodeficiency Virus - HIV

Key Points

Human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS). While therapy has become available to treat HIV infections, HIV remains a major public health problem, emphasizing the importance of continued diagnostic testing.

  • HIV Clinical Symptoms by Stage
    • Acute retroviral syndrome – fever, fatigue, rash, headache, lymphadenopathy, pharyngitis, myalgias, nausea, vomiting, diarrhea, and night sweats
      • Develops 1-4 weeks after exposure
      • Symptoms are too vague to distinguish acute HIV from other viral illnesses
    • Latency period without symptoms  
      • Lasts 2-8 years
    • Early chronic infection phase
      • Persistent fever
      • Diarrhea
      • Adenopathy
      • Chronic oral and cutaneous conditions
    • End stage disease (AIDS)
      • CD4+ <200 cells/µL
      • Opportunistic infections – viral, bacterial, fungal
      • Malignancies – Kaposi sarcoma, non-Hodgkin lymphoma (NHL), invasive cervical cancer, primary brain lymphoma
      • Chronic metabolic complications – dyslipidemia, impaired glucose tolerance, lipodystrophy, wasting
    Indications for Laboratory Testing

    At-risk patients

    • Symptoms of infection
    • Recent exposure to HIV-infected individual
    • History of high-risk behaviors
    • Pregnancy
    • Infant born to HIV-positive mother

    Guideline recommendations for HIV screening

    • CDC, 2010 (endorsed by ACOG, ACP)
      • All patients ages 13-64 years - in all health care settings
      • Patients at high risk for HIV - annual screening
      • Pregnant women - routine prenatal screening
    • USPSTF, 2013
      • All adolescents and adults ages 15 to 65 years
      • At-risk younger adolescents and older adults 
      • Pregnant women - including those who present in labor who are untested and whose HIV status is unknown
    Recommended Laboratory Testing

    Recommended Laboratory Testing

    Refer to testing algorithms

    • New CDC Proposed HIV Diagnostic Algorithm
    • Human Immunodeficiency Virus in Adults Testing algorithm

    Rapid Screening Test (Point-of-Care)

     

    Test Description

    • Can be performed in point-of-care settings
    • Provides results within minutes

    Limitation

    • Not positive until 3-5 weeks after exposure

    Follow-up

    • Refer to Human Immunodeficiency Virus in Adults Testing algorithm
    • Preliminary positive results must be confirmed with Western blot

    4th Generation HIV-1, HIV-2 Antibody/p24 Antigen  Screen

    ARUP Test

    Human Immunodeficiency Virus (HIV) Combo Antigen/Antibody (HIV-1/O/2) by ELISA, with Reflex to HIV-1/HIV-2 Antibody Differentiation by Multispot  2007980

    Test Description

    • 4th generation qualitative screen simultaneously detects HIV-1 p24 antigen and antibodies to HIV types 1 and 2
    • Discriminates between HIV-1 and HIV-2 antibodies

    Reflex Pattern

    • If HIV-1,2 combo antigen/antibodies screen is repeatedly reactive, confirmation by antibody differentiation test (Multispot) is added
    • This test reflects the multi-test algorithm proposed by the CDC and adopted by the Clinical Laboratory Standards Institute (CLSI) for diagnosis of HIV

    Follow-up

    • Refer to CDC Proposed HIV Diagnostic Algorithm
    • Indeterminate antibody differentiation testing requires HIV-1 NAAT testing using a separate specimen

    ARUP Test

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

    Test Description

    • 4th generation qualitative screen simultaneously detects HIV-1 p24 antigen and antibodies to HIV types 1 and 2
      • Antibody/antigen combination testing reduces diagnostic window by 5 to 7 days when compared to antibody only assay

    Reflex Pattern

    • If HIV-1,2 combo antigen/antibody screen is repeatedly reactive, confirmation by Western blot is added

    Limitation

    • Does not distinguish between the presence of HIV-1 p24 antigen, HIV-1 antibody, and HIV-2 antibody

    Follow-up

    • Refer to the 4th Generation Antigen/Antibody Combo test section of the Human Immunodeficiency Virus in Adults Testing algorithm
    • If Western blot confirmation is indeterminate or negative, proceed to NAAT (viral DNA) testing

    3rd Generation HIV-1, HIV-2 Antibody Screen

    ARUP Tests

    Human Immunodeficiency Virus Types 1 and 2 (HIV-1, HIV-2) Antibodies by CIA with Reflex to HIV-1 Antibody Confirmation by Western Blot 2005377

    Also available – HIV-1 only antibody screen with Western blot confirmation

    Human Immunodeficiency Virus Type 1 (HIV-1) Antibody by CIA with Reflex to HIV-1 Antibody Confirmation by Western Blot 2005375

    Test Description

    • Qualitative test detects antibodies to HIV types 1 and 2

    Reflex Pattern

    • If HIV-1,2 antibodies screen is repeatedly reactive, confirmation by Western blot is added

    Limitation

    • Not positive until 3-5 weeks after exposure

    Follow-up

    • Refer to the 3rd Generation Antibody Only Immunoassay section of the Human Immunodeficiency Virus in Adults Testing algorithm
    • If Western blot confirmation is
      • Indeterminate - repeat testing in 4 weeks
      • Negative – consider HIV-2 testing, if clinically indicated

    Confirmation test

    Western blot

    ARUP Test

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

    Test Description

    • Confirms HIV after preliminary positive rapid point-of-care test or HIV type 1 antibody screen
    • If Western blot confirmation is
      • Indeterminate - repeat testing in 4 weeks
      • Negative – consider HIV-2 testing, if clinically indicated

    Follow-up testing for confirmed HIV

    HIV Quantitative PCR

    ARUP Test

    Human Immunodeficiency Virus 1 RNA Quantitative Real-Time PCR 0055598

    Test Description

    • Quantitative test
    • Use
      • When 4th generation testing determines HIV is positive but type is unclear
      • To determine and monitor therapy in confirmed HIV cases

    HIV Qualitative

    ARUP Test

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

    Test Description

    • Qualitative test detects HIV-1 proviral DNA in infants
    • For initially positive test, recommend repeat testing at 1-2 months and 3-6 months of age to confirm diagnosis

    CD4 Lymphocyte Counts

    ARUP Test

    Lymphocyte Subset Panel  1 – CD4 Absolute Count Only 0095854

    Test Description

    • Quantitative test
    • Absolute CD4 count is sufficient for routine HIV monitoring
    • Order concurrently with HIV viral load testing for monitoring treatment and disease

Diagnosis

Indications for Testing

  • Symptomatic patients, those with recent exposure to HIV-infected individuals, infants born to HIV-infected mothers, pregnancy, or history of high-risk behaviors (intravenous drug use, multiple sexual partners, men having sex with men)

Laboratory Testing

Differential Diagnosis

Screening

  • Centers for Disease Control recommendations (endorsed by ACOG, ACP)
    • HIV screening in all patients ages 13-64 years who seek health care
    • Annual screening for high-risk patients
    • Routine screening as part of prenatal screen in pregnant females
  •  USPSTF recommended HIV screening for
    • Adolescents and adults ages 15 to 65 years
    • At-risk younger adolescents and older adults
    • Pregnant women - including those who present in labor who are untested and whose HIV status is unknown

Monitoring

  • Quantitative viral load and drug resistance testing allows for monitoring during treatment
  • The Public Health Service has recommended that T-helper cell (CD4) levels be monitored every 3-6 months in all HIV-infected persons

Clinical Background

Human immunodeficiency virus 1 (HIV-1) is thought to have originated as a zoonotic transmission from simian immunodeficiency virus (SIV)-infected primates, while human immunodeficiency virus 2 (HIV-2) is thought to have originated as a zoonotic transmission from SIV-infected Sooty Mangabey monkeys.

Epidemiology

  • Incidence – ~47,500 new HIV infections in 2010 (CDC)
  • Age – 18-30 years (peak)
  • Sex – M>F
  • Ethnicity – higher in African Americans
  • Transmission
    • Primarily via sexual contact (especially in men having sex with men)
    • Perinatally
    • Tissue transplantation
    • Blood-borne – not transmitted via saliva, insect vectors, or household contacts
    • Intravenous drug use

Organism

  • RNA single-stranded virus
  • Retroviridae family – includes HIV-1 and -2, and HTLV-1 and -2
  • HIV-1 and HIV-2 are etiologic agents of acquired immunodeficiency syndrome (AIDS)
    • HIV-1 accounts for the vast majority of HIV infections in the U.S. 
      • Includes group M and at least 10 subtypes (A through J)
        • Group O (for outlier)
        • Group N (for non-M, non-O)
    • HIV-2 is endemic in West Africa and rarely seen in U.S. 
      • Includes groups A through E

Pathophysiology

  • HIV localizes to the lymphoid organs
    • Infects the CD4+ helper cells and  T-cell lymphocytes
  • Viremia ensues post infection
  • Viral spread from local inoculation occurs quickly
    • ~30 billion virus particles produced in first weeks of infection

Clinical Presentation

  • Refer to Key Points section

Prevention

  • Can be prevented in 98% of infants of infected mothers by drug therapy during pregnancy, elective caesarian section, and refraining from breastfeeding
  • Use of condoms and needle exchange programs also reduce risk

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Human Immunodeficiency Virus Types 1 and 2 (HIV-1, HIV-2) Antibodies by CIA with Reflex to HIV-1 Antibody Confirmation by Western Blot 2005377
Method: Qualitative Chemiluminescent Immunoassay/Qualitative Western Blot

Screen for antibodies against HIV-1 and HIV-2

If test is repeatedly reactive, confirmation will be made by Western Blot

   
Human Immunodeficiency Virus (HIV) Combo Antigen/Antibody (HIV-1/O/2) by ELISA, with Reflex to HIV-1/HIV-2 Antibody Differentiation by Multispot 2007980
Method: Qualitative Enzyme-Linked Immunosorbent Assay/Qualitative Immunoassay

Appropriate test if acute HIV infection suspected

4th generation test screens for HIV-1 p24 antigen and antibodies to HIV-1 (groups M and O) and HIV-2

If screen is repeatedly reactive, antibody differentiation confirms and discriminates between HIV-1 and HIV-2 antibodies

Tests reflects the multi-test algorithm proposed by CDC and adopted by CLSI for diagnosis of HIV

   
Human Immunodeficiency Virus Types 1 and 2 (HIV-1/HIV-2) Antibody Differentiation by Multispot (Supplemental Use Only) 2009464
Method: Qualitative Immunoassay

Useful  as a supplemental assay for repeatedly reactive 3rd- or 4th-generation HIV screen tests, when following the CDC Proposed HIV Diagnostic Algorithm

This test cannot be used as a rapid screen nor as a follow-up for a positive rapid screen

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

Confirm HIV after positive rapid point-of-care test

   
Lymphocyte Subset Panel 1 - CD4 Absolute Count Only 0095854
Method: Quantitative Flow Cytometry

Determine T-cell (CD4) baseline levels to establish decision points for initiating P. jirovecii prophylaxis, antiviral therapy, and for monitoring treatment efficacy

Order concurrently with HIV viral load monitoring

 

Other lymphocyte panels are available; see list of additional tests available below

Human Immunodeficiency Virus 1 RNA Quantitative Real-Time PCR 0055598
Method: Quantitative Real-Time Polymerase Chain Reaction

Use in conjunction with clinical presentation as indicator of disease prognosis

Aids in assessing viral response to antiretroviral treatment

"Not Detected" does not rule out the presence of inhibitors or HIV-1 virus RNA concentrations below the assay detection level

 
Human Immunodeficiency Virus 1 RNA Quantitative bDNA 0020466
Method: Quantitative Branched Chain DNA

Use with clinical presentation as indicator of disease prognosis

Aids in assessing viral response to antiretroviral treatment

"Not Detected" does not rule out the presence of inhibitors or HIV-1 virus RNA concentrations below the assay detection level

Low positive values may occasionally be seen in specimens from uninfected patients

 
Human Immunodeficiency Virus 1 (HIV-1) by Qualitative PCR 0093061
Method: Qualitative Polymerase Chain Reaction

Detect HIV-1 proviral DNA in infants

Repeat testing at 1-2 months and 3-6 months of age

Do not use umbilical cord blood due to contamination with maternal blood

 
Human Immunodeficiency Virus Type 2 (HIV-2) Antibody by ELISA with Reflex to HIV-2 Supplemental 0051250
Method: Qualitative Enzyme Immunoassay/Qualitative Immunoassay

Screen for HIV-2 infection in patient with epidemiologic link to Africa

   
Human Immunodeficiency Virus 1, Genotype by Sequencing 0055670
Method: Reverse Transcription Polymerase Chain Reaction/Sequencing

Detect changes in the viral genome associated with drug resistance

Use in conjunction with CD4 measurement to monitor treatment efficacy

Because treatment failure can be caused by factors other than drug resistance, interpretation of resistance genotyping results must be made in conjunction with other clinical and laboratory information

Some insertions or deletions may be difficult to detect 

Absence of resistant mutations does not rule out possible reservoirs of resistant viruses undetectable by this assay

Specimens with HIV-1 RNA plasma levels <1,000 copies/mL may not provide adequate data due to polymorphisms in the priming areas of genome

Test does not detect HIV-1 populations <20% of the total population

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Human Immunodeficiency Virus Type 1 (HIV-1) Antibody by CIA with Reflex to HIV-1 Antibody Confirmation by Western Blot 2005375
Method: Qualitative Chemiluminescent Immunoassay/Qualitative Western Blot

Screen for presence of HIV-1 infection if HIV-1/HIV-2 combined antibody testing not available

Human Immunodeficiency Virus 1 RNA Quantitative Real-Time PCR with Reflex to Genotype 2002689
Method: Quantitative Real-Time Polymerase Chain Reaction/Sequencing

Panel includes Human Immunodeficiency Virus 1 RNA Quantitative Real-Time PCR and Human Immunodeficiency Virus 1, Genotyping

Use with clinical presentation as an indicator of disease prognosis and assess viral response to antiretroviral treatment

Human Immunodeficiency Virus 1 RNA Quantitative bDNA with Reflex to Genotype 2002688
Method: Quantitative Branched Chain DNA/Sequencing

Panel includes Human Immunodeficiency Virus 1 RNA Quantitative bDNA and Human Immunodeficiency Virus 1, Genotyping

Use with clinical presentation as an indicator of disease prognosis and assess viral response to antiretroviral treatment

Lymphocyte Subset Panel 2 - CD4  Percent and Absolute 0095885
Method: Quantitative Flow Cytometry

Absolute CD4 count is sufficient for routine HIV monitoring

Lymphocyte Subset Panel 3 - T-Cell Subsets (CD4 and CD8), Absolute Counts Only 0095853
Method: Quantitative Flow Cytometry
Absolute CD4 count is sufficient for routine HIV monitoring
Lymphocyte Subset Panel 4 - T-Cell Subsets Percent and Absolute, Whole Blood 0095950
Method: Quantitative Flow Cytometry

Absolute CD4 count is sufficient for routine HIV monitoring

Erythropoietin 0050227
Method: Quantitative Chemiluminescent Immunoassay

Absolute CD4 count is sufficient for routine HIV monitoring

HLA-B*5701 Associated Variant Genotyping for Abacavir Sensitivity 2002429
Method: Polymerase Chain Reaction/High Resolution Melt Analysis

Identify individuals at risk for abacavir sulfate hypersensitivity reaction (ABC HSR) prior to therapeutic treatment

Screening prior to reinitiation of treatment in individuals who have previously tolerated abacavir but whose HLA-B*5701 status is unknown

Clinical sensitivity/specificity – for immunologically confirmed ABC HSR, 98% and 99%, respectively

Analytical sensitivity/specificity – 99% for prediction of HLA-B*5701 carrier status by SNP rs2395029 genotyping

CD4+ T-Cell Recent Thymic Emigrants (RTEs) 2010179
Method: Quantitative Flow Cytometry

Assess thymic function in suspected severe combined immunodeficiency (SCID), DiGeorge syndrome and other T-cell immune deficiency disorders

Evaluate immune reconstitution during highly active antiviral therapy (HAART) in HIV patients and post chemotherapy and hematopoietic cell transplant