Infectious DiseasesTier 2Topic

Viral load assessment for - HIV

Role

HIV viral load (quantitative plasma HIV RNA) is the primary marker of antiretroviral treatment efficacy, tested at treatment initiation, after starting/changing therapy, and periodically thereafter to confirm and monitor viral suppression
Performed routinely in all patients on antiretroviral therapy, given its central role in guiding treatment decisions and confirming ongoing suppression

Suppression

Effective antiretroviral therapy suppresses viral replication to below the assay's detection threshold ("undetectable") within weeks to a few months of starting an effective regimen - failure to achieve or maintain suppression reflects either inadequate adherence, drug interactions/absorption issues, or genuine viral resistance

Monitoring schedule

Checked at baseline, then typically at 4-8 weeks after starting/changing therapy to confirm early response, then every 3-6 months once stably suppressed
A detectable result on established therapy should prompt adherence assessment as the first step (the most common cause of viral rebound) before pursuing resistance testing

Acting on the result

Confirmed inadequate adherence -> targeted adherence support rather than regimen change
Confirmed resistance (via genotypic resistance testing) despite good adherence -> regimen change guided by the resistance profile
Sustained undetectable viral load is also the basis for "undetectable = untransmittable" (U=U) counselling regarding sexual transmission risk

Adherence and resistance

Adherence as the dominant cause of viral rebound, antiretroviral resistance testing, U=U transmission risk counselling, pregnancy-specific viral load targets (aiming for undetectable before delivery to minimise vertical transmission)

U=U

U=U (undetectable = untransmittable) is now well-established evidence-based counselling - a patient with a sustained undetectable viral load on effective antiretroviral therapy does not sexually transmit HIV, which is an important, sometimes under-communicated point for patient counselling and reducing HIV-related stigma

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