Figure 2. Poor concordance between TaqMan v1 and Amplicor v1.5 at low plasma viral load levels (40.

–250 HIV RNA copies/mL by TaqMan v1). Between October 2009 and April 2010 plasma samples from British Columbia with low-level viremia (40–250 copies/mL) by the Roche TaqMan v1 assay (N = 1198) were systematically re-tested by the Amplicor v1.5 assay. Poor concordance was observed between TaqMan v1 and Amplicor v1.5 results, with 82% of values falling below the line of identity (red solid line). Points above the blue dashed line are samples in which TaqMan v1 underestimated pVL by ≥0.5 log₁₀ copies/mL relative to the Amplicor v1.5 assay.