maxRatio improves the detection of samples with abnormal amplification profiles on QIAgen's artus HIV-1 qPCR assay

Background: Accurate viral load (VL) determination is paramount to determine the efficacy of anti-HIV-1 therapy. The conventional method used, fit-point (FP), assumes an equal efficiency in the polymerase chain reaction (PCR) among samples that might not hold for low-input templates. An alternative approach, maxRatio, was introduced to compensate for inhibition in PCR. Methods: Herein, we assessed whether maxRatio could improve VL quantification using 2,544 QIAgen artus HI virus-1 RT-PCR reactions. The assay's standard dilutions were used to build external standard curves with either FP or maxRatio that re-calculated the VLs. Results: FP and maxRatio were highly comparable (Pearson's ρ=0.994, Cohen's  κ=0.885), and the combination of the two methods identified samples (n=41) with aberrant amplification profiles. Conclusions: The combination of maxRatio and FP could improve the predictive value of the assay.