Implementation and Early Outcomes of Laboratory Proficiency Testing Program for the National Wastewater Surveillance System, United States, 2024.

Underlying the core goals of the Centers for Disease Control and Prevention National Wastewater Surveillance System (NWSS) in the United States is the need for robust and reliable pathogen data. The rapid build-out of the NWSS network and participation of many laboratories with varying expertise in environmental molecular methods has resulted in a lack of method standardization and poor data comparability. Proficiency testing is a powerful strategy to address this challenge. We describe preliminary outcomes from 2 proficiency testing rounds with 38 total participating laboratories, where reported respiratory virus concentrations from replicate samples spanned roughly 2 orders of magnitude; the program identified key opportunities for improvement. Although still in its infancy, this program proved an effective tool for quantifying variability across the network, offering preliminary insights on method performance, and improving data quality through laboratory support. Our results suggest that wastewater proficiency testing for disease surveillance will improve data quality and strengthen the NWSS.