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HIV Basics: Clinical Tests and Guidelines
ACTHIV 2010
Zelalem Temesgen MD
Mayo Clinic
Topics
• Baseline laboratory evaluation
• Laboratory monitoring through the continuum of care
• Patients not on antiretroviral therapy
• Patients on antiretroviral therapy
• This presentation will not discuss any non-FDA-approved or investigational uses of any products/devices.
Sources
• Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents December 1, 2009
• http://aidsinfo.nih.gov/contentfiles/AdultandAdolescentGL.pdf
• Primary Care Guidelines for the Management of Persons Infected with Human Immunodeficiency Virus: 2009 Update by the HIV Medicine Association of the Infectious Diseases Society of America
• Clinical Infectious Diseases 2009; 49:651–81
Learning Objectives
• At the conclusion of this presentation, participants should be able to:
• Apply recommended best practices for baseline laboratory evaluation of the HIV-infected patient in your practice
• Apply recommended best practices for routine laboratory monitoring of the HIV-infected patient in your practice
Baseline Evaluation
• Classifying disease status
• Baseline safety laboratory tests
• Screening for comorbidities
• Screening for drug-resistance mutations
Classifying Disease Status
• Level of HIV viremia
• HIV-1 RNA (viral load)
• Immune function
• CD4 cell count and percentage
HIV-1 RNA
• Several FDA-approved assays
• Varying lower (48 – 400) and upper (100,000 – 10 million) limits of quantification
• Variable accuracy in the detection of non B HIV-1 subtypes
• Use the same assay in an individual patient over time
HIV-1 RNA (Viral Load)
• Measure HIV-1 RNA in plasma
• copies/mL
• Log10 changes (power of 10)• 0.5 log = 3-fold
• 1 log = 10-fold
• 3 log = 1000-fold
• Biologic variability about 0.3 log10
• Meaningful changes need to be at least
0.5 log in magnitude
What affects Viral Load?
• Intercurrent illness
• Vaccination
• Increases could be significant
• Return to baseline in 4 weeks
• Do not check viral load within 4 weeks of above events
CD4 Count
• T lymphocytes
• CD4 – provide help to other immune cells
• CD8 – mediate cytotoxicity
• CD4 measurement
• Total WBC
• Percent lymphocytes
• Percent CD4
What Affects CD4 Cell Counts?
• Intra subject variability approx. 25%
• Diurnal – 12:30 low; 20:30 peak
• Intercurrent illnesses
• Surgery
• Corticosteroids
• Interferon
• HTLV-I, splenectomy - increase
CD4 Percentage
• Less variable
• Meaningful changes > 3%
• 500/mm3 — 29%
• 200/mm3 — 14%
Baseline Safety Laboratory Tests
• CBC with differential
• Chemistry panel
• Liver function
• Creatinine
• Fasting glucose
• Fasting lipid profile
• Urinalysis
• Calculated creatinine clearance
Screening for Comorbidity and Coinfection
• Tuberculosis
• Viral hepatitis
• Sexually transmitted infections
• Toxoplasmosis
• If negative • Avoid primary exposure
• Recheck when CD4 < 100 for prophylaxis
Screening for Tuberculosis
• Tuberculin skin test
• Induration >5mm is positive
• Interferon γ release assay
• More consistent,
• less subjective
• Higher specificity (92-97%)
• Less cross reactivity with BCG and other mycobacteria
Screening for Hepatitis B
• Hepatitis B screen• HBsAg
• HBsAb
• HBcAb
• If negative HBsAg and HBsAb but positive HBcAb, check HBV DNA
• If negative screen – 3-dose HBV vaccine series
• 1-2 months post vaccine, HBsAb titer should be > 10 IU/mL
• Revaccinate with a 3-dose series
• Higher dose?, wait for higher CD4 count? CDC IDSA NIH HIVMA Guidelines 2009
Screening For Hepatitic C
• Anti-HCV antibody
• HCV RNA
•Confirmation of + anti-HCV
•If CD4 < 200
•Recent exposure to HCV
•Abnormal LFT
•Active IVDU
Screening for Hepatitis A
• Total anti-HAV
• If negative -vaccinate
Screening for Hepatitis A: Rationale
• Immunization recommended
• Those with increased risk of acquiring hepatitis A
• IVDU
• MSM
• Hemophiliacs
• Those with increased risk of decompensation if HAV acquired
• Chronic hepatitis B and hepatitis C
Sexually Transmitted Infections
• Syphilis
• VDRL
• RPR
• Antibody test
• Chlamydia
• Urine nucleic acid amplification test
• Gonorrhea
• Urine NAAT
• Trichomonas
Cervical Cancer Screening
• Cervical Pap smear at baseline and at 6 months
• Annually thereafter if negative
• If abnormal
• Colposcopy and biopsy
Baseline Drug-Resistance Testing
• Why?
• 6-16% risk that transmitted virus will be resistant to at least one antiretroviral drug
• 3-5% risk of resistance to more than one class
• Transmission of drug-resistant HIV strains leads to suboptimal virologic response
Baseline Drug-Resistance Testing
• Genotypic HIV drug resistance testing is recommended for persons with HIV infection when they enter into care regardless of whether therapy will be initiated immediately or deferred
• If therapy is deferred, consider repeat testing at the time of antiretroviral therapy initiation
Laboratory Monitoring of Established Patients
• Patients not on antiretroviral therapy
• Viral load q 3-4 months
• CD4 cell count q 3-4 months
• Fasting glucose q 6-12 months
• Fasting lipid profile q 6-12 months
• TB screening periodically, based on risk and symptoms
• STI screening periodically, based on risk and symptoms
Laboratory Monitoring of Established Patients on Antiretroviral Therapy
Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and
Adolescents December 1, 2009
Test Entry into care
Prior to Starting
ARTor
Switch
2-8 Weeks Post New
ART or Switch
Every 3-6
Months
Every 6 Months
Every 12 Months
HIV 1 RNA X X X X
CD4 cell count X X X
Resistance testing X X X
CBC X X X (ZDV)
X
Chemistry panel (ALT, AST, electrolytes, total and direct bilirubin, Cr)
X X X
Fasting glucose X X X (if abnormal)
X (if normal)
Fasting lipid profile X X X X
Urinalysis X X X (HIVAN)
X(TDF)
Thank You