What are the steps to diagnose HIV, including recommended labs, monitoring, and medications?

HIV Diagnosis, Monitoring, and Medication Management

HIV diagnosis should begin with a rapid HIV test or conventional enzyme-linked immunosorbent assay (ELISA) and be confirmed by Western blot or indirect immunofluorescence assay, followed by baseline laboratory testing and prompt initiation of antiretroviral therapy. 1

Step-by-Step Approach to HIV Diagnosis

Initial Screening

1. Screening Test Options:

   • Rapid HIV antibody test (results in minutes)
   • Combined HIV antibody/p24 antigen test (4th or 5th generation, preferred)
   • Conventional ELISA 1

2. Confirmatory Testing:

   • All reactive screening tests must be confirmed with Western blot or indirect immunofluorescence assay
   • If confirmatory testing is negative or indeterminate, repeat testing should be performed on a specimen collected 4 weeks after the initial reactive result 1

3. Special Testing Considerations:

   • For high-risk exposure within 72 hours: Rapid HIV test followed by PEP if negative
   • For suspected acute infection: HIV RNA testing may detect infection before antibody tests become positive 1
   • For infants <18 months: HIV DNA PCR testing (due to presence of maternal antibodies) 2

Post-Diagnosis Laboratory Evaluation

Baseline Testing (should be completed before starting ART but should not delay treatment initiation) 1:

1. HIV Disease Parameters:

   • CD4 cell count and percentage
   • HIV RNA viral load
   • HIV genotype resistance testing (for NRTI, NNRTI, and PI resistance)

2. General Health Assessment:

   • Complete blood count with differential
   • Comprehensive metabolic panel (kidney and liver function)
   • Lipid profile and fasting glucose
   • Urinalysis
   • Pregnancy test (if applicable)

3. Co-infection Screening:

   • Hepatitis A, B, and C serologies
   • Tuberculosis testing
   • Sexually transmitted infection screening
   • Toxoplasma gondii serology
   • Cryptococcal antigen (if CD4 <100/μL)

Monitoring During HIV Treatment

1. Initial Follow-up:

   • Assess adherence, tolerability, and HIV RNA level within 6 weeks of starting ART 1
   • If HIV RNA has not declined significantly and adherence is sufficient, perform genotypic resistance testing

2. Ongoing Monitoring:

   • HIV RNA levels: Every 3 months until suppressed for at least 1 year, then every 6 months
   • CD4 count: Every 3-6 months initially, can be reduced to annually once HIV is suppressed and CD4 >300 cells/μL
   • Complete blood count, metabolic panel, urinalysis: Every 3-6 months
   • Lipid profile: Annually or more frequently if abnormal or on lipid-altering medications

Antiretroviral Medications

First-Line Regimens (Preferred)

Integrase Strand Transfer Inhibitor (INSTI)-Based Regimens:

• Bictegravir/tenofovir alafenamide/emtricitabine (Biktarvy)
• Dolutegravir (Tivicay) + tenofovir/emtricitabine (Truvada or Descovy)
• Raltegravir (Isentress) + tenofovir/emtricitabine

Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI)-Based Regimens:

• Doravirine (Pifeltro) + tenofovir/emtricitabine
• Rilpivirine (Edurant) + tenofovir/emtricitabine (also available as Complera or Odefsey)

Protease Inhibitor (PI)-Based Regimens:

• Darunavir (Prezista) + ritonavir (Norvir) or cobicistat (Tybost) + tenofovir/emtricitabine

Common Medication Classes and Examples

1. Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs):

   • Tenofovir disoproxil fumarate (Viread)
   • Tenofovir alafenamide (component of Descovy)
   • Emtricitabine (Emtriva)
   • Lamivudine (Epivir)
   • Abacavir (Ziagen)

2. Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs):

   • Efavirenz (Sustiva)
   • Rilpivirine (Edurant)
   • Doravirine (Pifeltro)
   • Nevirapine (Viramune)

3. Protease Inhibitors (PIs):

   • Darunavir (Prezista)
   • Atazanavir (Reyataz)
   • Lopinavir/ritonavir (Kaletra)

4. Integrase Strand Transfer Inhibitors (INSTIs):

   • Bictegravir (component of Biktarvy)
   • Dolutegravir (Tivicay)
   • Raltegravir (Isentress)
   • Elvitegravir (component of Stribild, Genvoya)

5. Entry Inhibitors:

   • Maraviroc (Selzentry) - CCR5 antagonist
   • Enfuvirtide (Fuzeon) - Fusion inhibitor

Common Pitfalls and Caveats

1. Diagnostic Window Period:

   • Standard antibody tests may not detect HIV infection acquired within the previous 6 months
   • Combined antibody/antigen tests reduce this window but still may miss very recent infections 1

2. False Positives/Negatives:

   • False-positive ELISA results can occur in pregnancy or autoimmune disorders
   • False-negative results can occur during the window period or in advanced disease 3

3. Drug Resistance Testing:

   • Should be performed before starting ART but should not delay treatment initiation
   • InSTI resistance testing is not routinely recommended at baseline due to low prevalence of transmitted resistance 1

4. Medication Interactions:

   • Many antiretrovirals have significant drug-drug interactions
   • Always check for interactions when starting new medications

5. Immune Reconstitution Inflammatory Syndrome (IRIS):

   • Can occur after ART initiation, especially in patients with low CD4 counts
   • Presents as paradoxical worsening of pre-existing infections or unmasking of subclinical infections

By following this systematic approach to HIV diagnosis, monitoring, and treatment, providers can ensure optimal care for patients living with HIV, reducing morbidity and mortality while improving quality of life.