With the Covid-19 pandemic, testing became a priority in the thoughts and actions of people. Mass testing was recommended by the World Health Organization and is now a reality in many countries: thousands of people are tested every day, and their behaviour and decisions are based on the results they receive. At the moment, however, little is known about how well the public understands test results: to what extent are they considered accurate and do they influence people's thinking and behaviour?
For the first time, a study addressed these and other questions by analyzing the participants' estimates of the positive predictive value (i.e. the probability that individuals with a positive test result truly have the disease) and of the negative predictive value (i.e. the probability of being infection-free having tested negative) of the tests, the estimates of the diagnostic accuracy of tests (i.e. the rate of false positives and false negatives) as well as the participants' grasp of test results, their behavioural consequences, and the perceived usefulness of a short-term repetition of the test.
For their study, Katya Tentori and Stefania Pighin, respectively professor and researcher of the Center for Mind/Brain Sciences (CIMeC) of the University of Trento, recruited 566 participants from all over Italy, from South Tyrol to Sicily, balanced by gender and education level.
The researchers discovered, for example, that while the participants acknowledged the importance of information such as geographical location and presence or absence of Covid-19 symptoms, they failed to take this information into account when interpreting test results. This means that, when faced with a positive or negative result, the participants do not update the likelihood of being infected based on their geographical location (high or low risk area) or on the presence or absence of Covid-19 symptoms. The researchers also found that people tend to overestimate the probability that individuals with a positive test result truly have the disease, but underestimate it if the result is negative. They also discovered that the participants found more useful to repeat the test in the short term after a positive rather than a negative result, when scientific data would suggest otherwise.
In light of all this, the scholars of the University of Trento hope for the implementation of general education measures to help people better understand test results and adapt their behaviour accordingly. They observed, in fact, that the widespread use of swab tests has not yet been accompanied by adequate information on how to interpret test results.
"We believe it is essential to help the population fully understand the meaning and behavioural implications of their test results in order to make the most effective and correct use of these fundamental diagnostic tools. This would allow to avoid unpleasant consequences on a personal level and in the relationship with health authorities", Stefania Pighin and Katya Tentori added.
They concluded: "Mass testing is undoubtedly important to collect epidemiological information and manage the pandemic, but we must remember that it has an impact on a personal level, as it influences the behaviours and decisions of people. It is not difficult to imagine that a misunderstanding of test results can have significant consequences in terms of public health and citizens' well-being. For example, the systematic underestimation of false negatives could lead people to ignore safety measures and, if symptoms appear at a later time, could undermine the trust that citizens place in health care institutions.
Similarly, the confusion about the usefulness of a short-term repetition of the test after a positive result could give rise to an excessive use of tests even when not necessary, with all the serious consequences that this would entail on an organizational level".
About the article
The article "Public's understanding of swab test results for SARS-CoV-2: An online behavioural experiment during the April 2020 lockdown" was written by Stefania Pighin and Katya Tentori of the Center for Mind/Brain Sciences of the University of Trento (CIMeC).
The article was published in the "British Medical Journal (BMJ) Open" and is available in Open access from 17 January 2021.
The article is available at: http://dx.doi.org/10.1136/bmjopen-2020-043925