What laboratory tests are required prior to initiating Human Immunodeficiency Virus (HIV) treatment?

Laboratory Tests Required Prior to Initiating HIV Treatment

Before initiating antiretroviral therapy (ART) for HIV infection, a comprehensive panel of laboratory tests should be performed to assess HIV disease status, baseline organ function, and screen for coinfections and comorbidities. 1

Essential HIV-Specific Tests

• CD4 cell count and percentage (strong recommendation, high quality evidence) 1

  • Establishes baseline immune status
  • Some experts recommend obtaining 2 baseline measurements before making treatment decisions 1
  • CD8 cell count measurement is unnecessary as it doesn't influence clinical decision-making 1

• Plasma HIV RNA level (viral load) (strong recommendation, high quality evidence) 1

  • Establishes baseline viral activity
  • Helps assess prognosis and monitor response to therapy

• HIV genotype resistance testing (strong recommendation, high quality evidence) 1

  • Essential to detect transmitted drug resistance
  • Reverse transcriptase and protease genotype preferred in antiretroviral-naive patients
  • Integrase genotype testing is not routinely recommended for treatment-naive patients unless there's suspicion of transmitted integrase inhibitor resistance 1

• HLA-B*5701 testing (strong recommendation, high quality evidence) 1

  • Required before prescribing abacavir to identify patients at high risk for hypersensitivity reactions

Safety Laboratory Tests

• Complete blood count with differential 1

  • Assesses baseline hematologic parameters

• Serum chemistry panel 1

  • Electrolytes, blood urea nitrogen, creatinine
  • Liver function tests (ALT, AST, bilirubin, alkaline phosphatase)
  • Albumin
  • Fasting glucose
  • Lipid profile (fasting)

• Urinalysis 1

  • Assesses for proteinuria, hematuria, and glucosuria
  • Particularly important when considering tenofovir-containing regimens

• Pregnancy test (for people of childbearing potential) 1

Coinfection and Comorbidity Screening

• Hepatitis virus screening (strong recommendation, high quality evidence) 1

  • Hepatitis B surface antigen (HBsAg)
  • Hepatitis B surface antibody (HBsAb)
  • Hepatitis B core antibody (anti-HBc)
  • Hepatitis C antibody
  • Hepatitis A antibody (total)

• Tuberculosis screening (strong recommendation, high quality evidence) 1

  • Tuberculin skin test (TST) or interferon-gamma release assay (IGRA)

• Toxoplasma gondii IgG antibody (strong recommendation, moderate quality evidence) 1

  • Identifies patients at risk for toxoplasmosis reactivation

• Sexually transmitted infection (STI) screening 1

  • Syphilis serology
  • Gonorrhea and chlamydia testing at exposed sites

• Cryptococcal antigen

  • Recommended if CD4 count is <100 cells/μL 1

Special Considerations

• Coreceptor tropism assay

  • Only required if considering a CCR5 entry inhibitor like maraviroc 1

• Glucose-6-phosphate dehydrogenase

  • Screen for deficiency in appropriate racial or ethnic groups 1

Clinical Pitfalls to Avoid

1. Do not delay ART initiation while waiting for all laboratory results if rapid start is clinically appropriate 1, 2

   • Immediate initiation of ART has been associated with higher rates of retention in care and viral suppression

2. Verify HIV diagnosis if no prior documentation exists 1

   • Patients without documentation should have HIV serologic testing performed

3. Consider baseline variability in CD4 counts

   • Substantial variation can occur, especially during acute illness 1

4. Recognize that transmitted drug resistance is common

   • Genotype testing is essential even if treatment is deferred 1

5. Be aware of potential false-positive HIV test results

   • May occur in patients with autoimmune disorders or during pregnancy 1
   • Confirmatory testing is essential before initiating treatment 3

The laboratory assessment provides critical information for selecting appropriate initial ART regimens, identifying potential complications, and establishing baseline parameters for monitoring treatment response and toxicity. While comprehensive testing is ideal, the need for rapid ART initiation should be balanced against waiting for all test results, particularly in patients with advanced disease.