Measurement of HIV RNA in patients infected by subtype C by assays optimized for subtype B results in an underestimation of the viral load.

Quantitation assays of HIV-1 RNA used currently were designed and optimized for subtype B viruses. However, infection with non-B HIV viruses has become more common worldwide. Unfortunately, little information is available regarding the suitability of these assays for measurement of viral load in specific non-B subtypes.