Testing behaviour and positivity for SARS-CoV-2 infection: Insights from web-based participatory surveillance

Background: Voluntary testing for SARS-CoV-2 infection is an integral component of an effective response to the COVID-19 pandemic. It is essential to identify populations at a high risk for infection but who are less likely to present for testing. Here, we use internet-based participatory surveillance data from the Netherlands to identify sociodemographic and household factors that are associated with a lower propensity to be tested and, if tested, with a higher risk of a positive test result. Methods: Multivariable analyses using generalised estimating equations for binomial outcomes were conducted to estimate the adjusted odds ratios of testing and of positivity associated with participant and household characteristics. Results: Based on five months (17 November 2020 to 18 April 2021) of weekly surveys obtained from 12,026 participants, males (adjusted odds ratio for testing (OR t ): 0.92; adjusted odds ratio for positivity (OR p ): 1.30, age-groups <20 (OR t 0.89; OR p 1.27) 50-64 years (OR t 0.94; OR p 1.06) and 65+ years (OR t 0.78; OR p 1.24), diabetics (OR t 0.97; OR p 1.06), and sales/administrative employees (OR t 0.93; OR p 1.90) were distinguished as lower propensity/higher positivity factors. Conclusions: The factors identified using this approach can help identify potential target groups for improving communication and encouraging testing among those with symptoms and thus increase the effectiveness of testing, which is essential for the response to the COVID-19 pandemic and for public health strategies in the longer term .