Maraviroc is considered for salvage antiretroviral therapy in a treatment-experienced patient. Which laboratory test is mandatory before prescribing it?

• A Viral tropism assay to confirm CCR5-tropic virus ✓
• B Genotypic resistance testing of reverse transcriptase
• C HLA-B*57:01 typing
• D Quantitative HIV DNA PCR for proviral load

Explanation

Maraviroc blocks the CCR5 coreceptor on host cells and has no activity against CXCR4-tropic or dual-tropic virus. B tropism assay must document exclusive CCR5 use before starting the drug, otherwise therapy fails despite full susceptibility of other steps. Genotypic RT testing guides NRTI and NNRTI choice but says nothing about coreceptor usage, and proviral DNA load has no role in selecting entry inhibitors.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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