Figure 5. Systematic underestimation of plasma viral load by TaqMan v1 in a minority of patients.

A minority (2.4%) of samples had viral loads underestimated by >0.5 log₁₀ copies/mL by TaqMan v1 after re-testing with Amplicor v1.5. Depicted here is the viral load history of one representative patient showing systematic underestimation of viral load by TaqMan v1 when compared to results obtained by re-testing samples with the Amplicor v1.5, TaqMan v2 and/or Abbott assays. TaqMan v1 viral load results are shown as solid triangles (▴) joined by a solid line. Overlaid are the corresponding results from the Amplicor v1.5 (solid squares ▪), TaqMan version 2 (unshaded triangles Δ) and Abbott (unshaded squares γ) assays where available. For this patient TaqMan v1 systematically under-reported pVL by an average of 1.3 log₁₀ copies/mL over a period of 18 months.