Purpose of review: HIV drug resistance testing using blood plasma or dried blood spots forms part of international guidelines. However, as the clinical utility of assessing drug resistance in other body compartments is less well established, we review this for blood cells and samples from other body compartments.
Recent evidence: Although clinical benefit is not clear, drug resistance testing in blood cells is often performed when patients with suppressed plasma viral loads require a treatment substitution. In patients with HIV neurocognitive disease, cerebral spinal fluid (CSF) drug resistance is rarely discordant with plasma but has nevertheless been used to guide antiretroviral drug substitutions. Cases with HIV drug resistance in genital fluids have been documented but this does not appear to indicate transmission risk when blood plasma viral loads are suppressed.
Summary: Drug-resistant variants, which may be selected in tissues under conditions of variable adherence and drug penetration, appear to disseminate quickly, and become detectable in blood. This may explain why drug resistance discordance between plasma and these compartments is rarely found. Partial compartmentalization of HIV populations is well established for the CSF and the genital tract but other than blood plasma, evidence is lacking to support drug resistance testing in body compartments.
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