Since the start of the COVID-19 pandemic, countries have been advised by WHO to expand testing in order to detect COVID-19 cases early, ensure their isolation, trace and isolate their contacts, and determine the epidemiological situation as accurately as possible.
However, for a number of reasons, including the stage of the epidemic, the national response strategy, and differences in the capacity for testing, countries have used different criteria to decide who to test.
Details on current testing criteria as of 16th April for a selection of countries in the WHO European region are available from the COVID-19 Health Systems Response Monitor (HSRM) and summarized in the figure below, with data for 41 countries available. These countries are at various stages of the pandemic, and this might explain some of their differences in testing strategies. Initially, as a few imported cases were detected, the testing was primarily focussed on symptomatic travellers arriving from high-risk areas (with the geography of what were considered high-risk areas progressively expanding) and their symptomatic contacts. This focus on imported cases has shifted in most countries, as they started registering community spread.
As of 16th April, among symptomatic population groups, most countries test people with severe symptoms (mainly those needing hospitalisation). The testing of symptomatic cases in groups at high risk and among health- and social care staff is also done quite broadly, although not in all countries, and testing in social care seems to lag behind. For example, in the Netherlands, symptomatic health care staff are required to self-isolate if they display symptoms of COVID-19, but they are not tested routinely. Strategies also vary widely in terms of testing residents of long-term care institutions, with some countries testing all residents with symptoms, while others (e.g. France, the Netherlands and the United Kingdom) only test few or selected cases in order to determine if there is an outbreak in an institution. When interpreting the figure, it is important to bear in mind that countries differ in details of strategies (e.g. there may be regional differences as well as set priorities depending on laboratory capacity) as well as in the scale of implementation.
As testing capacity in countries expands, more countries start to pilot areas with community-wide testing (e.g. Cyprus and the Veneto region in Italy), however none of the 41 countries reviewed have implemented this at the national level.
Figure 1. Selected categories of the symptomatic population groups tested nationally in 41 countries
In countries with community spread that have restricted testing capacity, WHO recommends to prioritise testing of at-risk and vulnerable groups, all symptomatic health care workers, and at first symptomatic cases in closed settings, such as long-term care institutions.
Marina Karanikolos, Selina Rajan, Bernd Rechel