Comparison of RT-qPCR and Digital PCR Methods for Wastewater-Based Testing of SARS-CoV-2 (preprint)

Wastewater-based epidemiology is an important tool for monitoring SARS-CoV-2 and other molecular targets in populations, using wastewater as a pooled sample. We compared the sensitivity, susceptibility to inhibition, and quantification of reverse transcription quantitative PCR (RT-qPCR), microfluidic well digital RT-PCR (RT-dPCR), and droplet digital RT-PCR (RT-ddPCR) measurements of SARS-CoV-2 (N1 gene target) and Pepper Mild Mottle Virus (PMMoV) RNA in 40 wastewater RNA extracts. All three methods were highly sensitive, but appeared less accurate at very low concentrations. Lower inhibition was observed for RT-ddPCR than RT-qPCR with both SARS-CoV-2 and PMMoV targets, but inhibition appeared to be mitigated by dilution of template RNA. The concentrations of N1 and PMMoV from all three methods were significantly correlated (Pearson's r=0.97-0.98 for N1 and r=0.89-0.93 for PMMoV), although RT-qPCR reported higher concentrations than digital methods. Taken together, this study provides support for the application of all three methods in wastewater-based epidemiology, with additional guidelines for the use of RT-qPCR.

Operationalizing a routine wastewater monitoring laboratory for SARS-CoV-2 (preprint)

Wastewater-based testing for SARS-CoV-2 is a novel tool for public health monitoring, but additional laboratory capacity is needed to provide routine monitoring at all locations where it has the potential to be useful. Few standardization practices for SARS-CoV-2 wastewater analysis currently exist, and quality assurance/quality control procedures may vary across laboratories. Alongside counterparts at many academic institutions, we built out a laboratory for routine monitoring of wastewater at the University of California, Berkeley. Here, we detail our group's establishment of a wastewater testing laboratory including standard operating procedures, laboratory buildout and workflow, and a quality assurance plan. We present a complete data analysis pipeline and quality scoring framework and discuss the data reporting process. We hope that this information will aid others at research institutions, public health departments, and wastewater agencies in developing programs to support wastewater monitoring for public health decision-making.