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 ART initiation and modification. Fasting blood sugar (FBS) is also performed upon entry into care and during ART initiation or modification. Lipid levels are determined upon entry into care.  

Coreceptor Tropism Testing  

Coreceptor tropism testing is used during ART 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 ART and the need to initiate prophylaxis for opportunistic infections before ART initiation. It is also the strongest predictor of subsequent disease progression and survival. CD4 T-cell count is used to assess immunologic response after ART initiation and the need for discontinuing prophylaxis for opportunistic infections. An adequate CD4 response for most patients on ART is defined as an increase in CD4 count in the range of 50-150 cells/mm³ in the first year of ART 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 ART initiation and periodically after initiation if indicated because treatment of these coinfections may affect the choice of ART 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 ART will be started immediately or deferred, and during ART initiation and modification. Genotypic testing is the preferred resistance testing to guide the selection of initial regimen in ART-naïve patients. It is recommended that prior to starting ART, 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 are 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 ART. 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 ART initiation or modification due to virologic failure, provided that the patient is adherent to their ART 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 ART.  

Urinalysis  

Urinalysis is performed upon entry into care.  

Other Tests  

Other tests include tests for cancer, sexually transmitted infections (STIs), and tests for determining the risk of opportunistic infections. A pregnancy test is recommended in women who will be started on Efavirenz (EFV).