HIV Phenotypic Susceptibility Testing (Serum/Plasma)

What This Test Measures

This test evaluates the virus’s response to various antiretroviral medications by measuring how effectively each drug inhibits viral replication. Results are typically reported as minimum inhibitory concentrations (MICs) for each drug class, indicating whether the virus is likely to be resistant or sensitive.

Why It Matters in Treatment

Understanding drug susceptibility helps prevent resistance—when the virus adapts to a drug and becomes harder to treat. It’s especially important for patients on long-term therapy or those with viral strains that may have developed resistance to previous treatments.

Sample Collection and Preparation

A blood sample (serum or plasma) is collected and sent to a lab where the virus is isolated and exposed to multiple antiretroviral drugs. The test measures how much the virus grows (or doesn’t) in the presence of each drug, helping identify which ones remain effective.

How Results Are Interpreted

Results are presented as a susceptibility profile, listing drugs (e.g., protease inhibitors, nucleoside reverse transcriptase inhibitors) and their effectiveness. A virus labeled ‘sensitive’ to a drug means it’s likely to respond well; ‘resistant’ means the drug may not work as intended.