Hiv Laboratory Testing

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Contents 1 More Specific Terms 2 Introduction 3 Laboratory 4 Notes 5 More General Terms 6 Additional Terms 7 References

More Specific Terms

• HIV 1+2 Ab in serum
• HIV p24 antigen
• HIV resistance testing
• HIV-1 coreceptor tropism (Trofile)
• HIV1 RNA viral load
• HIV1 serology; HIV1 antibody (HIV1 EIA/ELISA, immunoblot)
• human immunodeficiency virus-1 (HIV1) western blot
• rapid HIV test (point of care HIV test)

Introduction

• HIV screening is done with HIV ELISA or other rapid HIV test
• confirmatory testing is done with HIV1 western blot
• early detection using nucleic acid amplification may become standard of care [2]

Laboratory

• specific HIV-1 antibodies* are not detectable until 4-12 weeks after initial infection

• screening with ELISA* for antibody to HIV-1 (99% sensitivity & specificity)
• Oraquick Rapid HIV-1 Antibody Test available 2003
• HIV Ag/Ab Combo assay to detect both HIV p24 antigen & antibodies FDA-approved 6/21/10
• p24 antigen testing is generally positive just after onset of symptoms of seroconversion, before development of antibodies
• confirmatory Western blot* for antibodies to virus- specific proteins: a positive western blot consists of the presence of bands for:
• p24; b) gp41 & c) gp120 or gp160
• seronegative HIV1 infections are rare, but potentially lethal [6]

• quantitative HIV-1 RNA levels

• reverse-trancriptase polymerase chain reaction ( RT-PCR)
• branched chain DNA ( bDNA) assay
• nucleic acid sequence-based assay (NASBA)
• high levels of HIV-1 RNA (500,000- 21 million copies/ mL) are detected in plasma before the detection of specific anti-HIV-1 antibodies
• the high level of viremia decreases 100-10,000 fold coincident with the development of the specific anti-HIV-1 humoral immune response - it is thought that cytotoxic T-cells are responsible for this decline in HIV1 viral load
• post- seroconversion viral load ( HIV RNA determined by PCR) is the best predicator of long-term prognosis
• post- seroconversion HIV RNA > 30,000 copies/ mL are associated with a high risk of disease progression
• identification of acute HIV infection with quantitative HIV-1 RNA levels combined with aggressive early treatment may

• reduce severity of chronic infection
• prevent transmission to sexual contacts [8]

• HIV1 viral load
• independent predictor of disease progression [3]
• poorly predicts decline in CD4 count [7]
• responds to initiating or changing therapy within 4-8 weeks (>= 1 log decrease in HIV RNA)
• a decrease in HIV RNA of more than 1 log is associated with treatment benefit
• frequent monitoring of HIV-1 RNA levels for the 1st year to detect treatment failure [11]
• routine every 3-4 months & monthly after change in therapy

• complete blood count ( CBC) with differential

• lymphopenia may develop during acute seroconversion
• atypical lymphocytosis may follow resolution of symptoms associated with seroconversion

• serum chemistries (every 6-12 months)

• renal function tests
• serum transaminases
• serum glucose
• lipid panel

• serology

• serologic testing for syphilis
• Toxoplasma gondii IgG
• Cytomegalovirus ( CMV) IgG
• hepatitis B serology & hepatitis C serology

• CD4 count

• best predictor of risk of disease progression
• average rate of decline is 80-90/ uL/year
• viral load does NOT predict decline [7]
• routine every 3-4 months [6]

• tuberculin skin testing annually [6] unless PPD+ or with active tuberculosis
• Papanicolaou (Pap) smear for women
• glucose-6-phosphate dehydrogenase ( G6PD) in erythrocytes (baseline)
• HIV1 resistance testing, all HIV1 patients [6,11]
• CCR5 gene mutation analysis (4 Loincs)

• variations in CCR5 are associated with susceptibility or resistance to HIV1

• HIV-1 coreceptor tropism testing

• determines eligibility for maraviroc ( Selzentry) therapy by determinng variations in the HIV-1 envelope V3 loop by PCR [10]
• HIV1 tropism testing determines ability of HIV-1 isolate to infect & replicate in monocytes [9]

Notes

• The requirement for informed consent for HIV testing has been repealed, effective Aug 17 2009.
• Confidentiality for HIV testing to be consistent with HIPPA guidelines for other laboratory tests. [5]
  
• Previously:

• testing could be done only after informed consent
• legal guardians could sign consent
• sexually active children over 12 could give their own consent
• only the person who gave consent could be given the results of the test
• others could be notified only is written permission is obtained from the person tested

More General Terms

• laboratory medicine (clinical pathology)

Additional Terms

• human immunodeficiency virus-1

References

1. Veterans Administration, Mather CA
2. Truong HH et al, Routine surveillance for the detection of acute and recent HIV infections and transmission of antiretroviral resistance. AIDS 2006, 20:2193 PMID: [1]
   - Priddy FH et al, Detection of acute HIV infections in an urban HIV counseling and testing population in the United States. J Acquir Immun Defic Syndr 2006 (ePub)
3. Centers for Disease Control and Prevention, Missed Opportunities for earlier diagnosis of HIV infection - South Carolona, 1997-2005 MMWR Morb Mortal Wkly Rep 2006, 55:1269 PMID: [2]
4. Voetsch A et al HIV Testing Among High School Students - United States, 2007 MMWR June 26, 2009 / 58(24);665-668 [3]
5. Federal Register: July 16, 2009 (Volume 74, Number 135) Rules and Regulations: Page 34500-34503] From the Federal Register Online via GPO Access [4] DOCID:fr16jy09-3 DEPARTMENT OF VETERANS AFFAIRS Elimination of Requirement for Prior Signature Consent and Pre- and Post-Test Counseling for HIV Testing ACTION: Final rule. [5]
6. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, American College of Physicians, Philadelphia 1998, 2006, 2009
7. Rodriguez B et al, Predictive value of plasma HIV RNA level on rate of CD4 T-cell decline in untreated HIV infection. JAMA 2006, 296:1498 PMID: [6]
8. Journal Watch 25(11):88, 2005 Pilcher CD, Fiscus SA, Nguyen TQ, Foust E, Wolf L, Williams D, Ashby R, O'Dowd JO, McPherson JT, Stalzer B, Hightow L, Miller WC, Eron JJ Jr, Cohen MS, Leone PA. Detection of acute infections during HIV testing in North Carolina. N Engl J Med. 2005 May 5;352(18):1873-83. PMID: [7]
9. O'Brien WA et al HIV-1 tropism for mononuclear phagocytes can be determined by regions of gp120 outside the CD4-binding domain Nature 1990, 348:69-73 PMID: [8]
10. HIV-1 Coreceptor tropism Quest Diagnostics [9]
11. Thompson MA et al Antiretroviral Treatment of Adult HIV Infection 2010 Recommendations of the International AIDS Society- USA Panel JAMA. 2010;304(3):321-333 <PubMed> PMID: [10] <Internet> [11]

HIV laboratory testing