Journal: medRxiv

Article Title: Bio-Rad and QIAGEN digital PCR platforms provide equivalent quantification for wastewater-based SARS-CoV-2 surveillance

doi: 10.64898/2026.01.20.26344437

Figure Lengend Snippet: Quantitative comparison of SARS-CoV-2 targets between Bio-Rad QX200 ddPCR and QIAGEN QIAcuity dPCR platforms across all concentration ranges. Scatter plots showing hyperwelled (merged triplicate) concentrations for (A) N1 gene target and (B) N2 gene target. Each point represents a single wastewater sample (n = 95) plotted as log 10 copies L -1 on both axes. Samples are color-coded by concentration bin: high (red, 5×10 4 to 5×10 5 copies L -1 , n=31), medium (orange, 5×10 3 to 5×10 4 copies L -1 , n=32), and low (blue, 1×10 3 to 5×10 3 copies L -1 , n=31). Solid black line represents perfect 1:1 agreement; dashed line showed linear regression fit. Linear regression equations, R 2 values, and 95% confidence intervals (gray shading) are displayed for each target. Mean absolute differences between platforms: N1 = 0.10 log copies L -1 , N2 = 0.06 log copies L -1 . All correlations significant at p < 0.001.

Article Snippet: For positive controls, we used genomic SARS-CoV-2 RNA positive control from strain 2019nCoV/USA-WA1/2020 (VR-1986D, ATCC Bethesda, MD), and the positive controls were included with each plate in duplicate for the N1 and N2 assays.

Techniques: Comparison, Concentration Assay

Journal: medRxiv

Article Title: Bio-Rad and QIAGEN digital PCR platforms provide equivalent quantification for wastewater-based SARS-CoV-2 surveillance

doi: 10.64898/2026.01.20.26344437

Figure Lengend Snippet: Platform comparison of SARS-CoV-2 quantification stratified by concentration bin. Box plots showing distribution of log 10 -transformed concentrations (copies L -1 ) for (A) N1 gene target and (B) N2 gene target across low, medium, and high concentration bins. Bio-Rad QX200 data shown in blue; QIAGEN QIAcuity data shown in green. Each box represents the interquartile range (IQR, 25 th -75 th percentile), with the horizontal line indicating the medium. Whiskers extend to 1.5x IQR or the most extreme data point within this range. Individual data points are overlaid as semi-transparent dots to show data distribution (n=31 for high and low bins, n=32 for medium bin). Asterisks indicate statistically significant differences between platforms within each bin as determined by linear mixed effects modeling (*p < 0.05, **p < 0.01, ***p < 0.001). Note that all statistically significant differences are ≤ 0.13 log copies L -1 . Sample numbers are indicated for each concentration bin. Both platforms successfully quantified 100% of samples across all bins.

Article Snippet: For positive controls, we used genomic SARS-CoV-2 RNA positive control from strain 2019nCoV/USA-WA1/2020 (VR-1986D, ATCC Bethesda, MD), and the positive controls were included with each plate in duplicate for the N1 and N2 assays.

Techniques: Comparison, Concentration Assay, Transformation Assay

Journal: medRxiv

Article Title: Bio-Rad and QIAGEN digital PCR platforms provide equivalent quantification for wastewater-based SARS-CoV-2 surveillance

doi: 10.64898/2026.01.20.26344437

Figure Lengend Snippet:

Article Snippet: For positive controls, we used genomic SARS-CoV-2 RNA positive control from strain 2019nCoV/USA-WA1/2020 (VR-1986D, ATCC Bethesda, MD), and the positive controls were included with each plate in duplicate for the N1 and N2 assays.

Techniques: