National and regional modeling of distinct RSV seasonality thresholds for antigen and PCR testing in the United States.

Background: PCR tests now outnumber antigen tests for the diagnosis of respiratory syncytial virus (RSV) infection in the US. Recent analyses have shown that the traditional 10% positivity threshold to define an RSV season by rapid antigen testing was inappropriate for real-time PCR testing, for which 3% positivity appeared more appropriate.

Objective: To respectively model antigen (10%) and PCR (3%) positivity thresholds at national and regional levels using a large dataset of RSV testing results from US hospital-affiliated laboratories.