Antiretroviral Therapy for HIV-Infected Adults Diagnostics

Laboratory Tests and Ancillaries

Blood Tests  

Complete blood count (CBC), transaminase levels, blood urea nitrogen (BUN), creatinine, serum electrolytes (eg Na, K, Cl, HCO₃) should be performed upon entry into care and during antiretroviral therapy initiation and modification. Fasting blood sugar (FBS) is also performed upon entry into care and during antiretroviral therapy initiation or modification. Lipid levels are determined upon entry into care.  

Coreceptor Tropism Testing  

Coreceptor tropism testing is used during antiretroviral therapy initiation and modification whenever C-C chemokine receptor type 5 (CCR5) inhibitor (eg Maraviroc) is being considered. It is also considered if patients exhibit virologic failure on Maraviroc or any CC5 inhibitor. Phenotypic tropism assay is preferred to determine HIV-1 coreceptor usage. European guidelines recommend performing genotypic tropism assay in the determination of coreceptor usage in patients with HIV RNA levels of >1,000 copies/mL and preferably in patients with HIV RNA levels ≤1,000 copies/mL.  

CD4 T-cell Count  

CD4 T-cell count serves as a major indicator of immune function. It is one of the key factors in deciding the urgency to start antiretroviral therapy and the need to initiate prophylaxis for opportunistic infections before antiretroviral therapy initiation. It is also the strongest predictor of subsequent disease progression and survival. CD4 T-cell count is used to assess immunologic response after antiretroviral therapy initiation and the need for discontinuing prophylaxis for opportunistic infections. An adequate CD4 response for most patients on antiretroviral therapy is defined as an increase in CD4 count in the range of 50-150 cells/mm³ in the first year of antiretroviral therapy with an accelerated response in the first 3 months of therapy expect in patients with a low starting CD4 count and in those with an advanced age who may show a blunted increase despite virologic suppression.

Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) Infection Screening  

HBV and HCV screening is recommended before antiretroviral therapy initiation and periodically after initiation if indicated because treatment of these co-infections may affect the choice of antiretroviral therapy and the likelihood of drug-induced hepatotoxicity.  

HIV Antibody Testing  

HIV antibody testing is done if there is no prior documentation available or if HIV RNA is below the assay’s limit for detection.  

HIV Drug Resistance Testing  

HIV drug resistance testing should be done upon entry into care, regardless of whether antiretroviral therapy will be started immediately or deferred, and during antiretroviral therapy initiation and modification. Genotypic testing is the preferred resistance testing to guide the selection of initial regimen in antiretroviral therapy-naïve patients. It is recommended that prior to starting antiretroviral therapy, a repeat HIV-viral load (VL) level and CD4 count must be obtained to have a baseline in assessing the patient’s subsequent response. The standard genotypic drug resistance testing for reverse transcriptase and protease gene mutations is recommended, and testing for integrase gene mutations is performed if resistance to transmitted integrase strand transfer inhibitor (INSTI) is suspected in newly diagnosed HIV or in patients who acquired HIV after receiving long-acting Cabotegravir (CAB-LA) as a pre-exposure prophylaxis. Lastly, viral amplification for drug resistance testing is recommended in patients with HIV RNA levels of <1,000 copies/mL.
 
HLA-B*5701 Screening  

HLAB-5*5701 screening is recommended prior to initiating Abacavir (ABC)-containing regimen to reduce the risk of hypersensitivity reaction.  

Plasma HIV RNA (Viral Load)  

The plasma HIV RNA assesses the level of HIV viremia. It is the most important indicator of initial or sustained response to antiretroviral therapy. HIV RNA levels should be measured in all HIV-infected patients upon start of care and therapy then on a regular basis thereafter. The pretreatment viral load level is taken into consideration in selecting the initial antiretroviral (ARV) regimen due to poorer responses in patients with high baseline viral load.  

Optimal viral suppression is generally defined as a viral load persistently below the level of detection (<20 copies/mL), depending on the assay used. Viral suppression is generally achieved in 8-12 weeks after antiretroviral therapy initiation or modification due to virologic failure, provided that the patient is adherent to their antiretroviral therapy regimen and does not develop resistance to the prescribed drugs. The early detection of virologic failure allows better preservation of efficacy of second-line regimens. In settings where resources are limited, the measurement of plasma viral load is not required prior to the initiation of antiretroviral therapy. 

Urinalysis  

Urinalysis is performed upon entry into care to assess for evidence of proteinuria or hematuria. 

Other Tests  

Other tests include tests for cancer, STIs (eg gonorrhea, chlamydia, trichomoniasis, syphilis), and tests to screen for possible co-infections (eg viral hepatitis A, B, and C, latent TB, varicella, measles, cryptococcus, toxoplasmosis). A pregnancy test is recommended in women who will be started on Efavirenz (EFV). A chest X-ray, cytology, cervical and/or anal Pap test, serum testosterone, glucose-6-phosphate dehydrogenase test may be performed if needed under certain circumstances.