The key question that needs to be answered is whether the figures published at some date (attempt to) include all tests conducted up to that date.īecause the reporting of tests can take several days, for some countries figures for the last few days may not yet be complete. In order to assess the reliability of aggregate testing data, it needs to be clear if heterogeneous data is being summed together.ħ) What period do the published figures refer to?Ĭumulative counts of the total number of tests should make clear the date from which the count begins. The scope of testing data should be made explicit by the source.Ħ) Are all regions and laboratories within a country submitting data on the same basis?Īnswers to the questions above may vary from region to region. To be reliably included in test counts, it needs to be explicit whether such categories reflect the number of people who are awaiting test results or have tested negatively.ĥ) Do the figures include all tests conducted in the country or only some?įigures reported by countries may only be partial if not all laboratories are reporting to the central authority. Many sources report the number of individuals who are ‘suspected’ or have been ‘ruled out’. It needs to be clear whether or not figures for the total number of tests performed, or the number of people tested, include negative test results, as well as the number of tests that are pending results. The data description should state clearly what is counted.Ĥ) Are negative results included? Are pending results included? In the latter case, it needs to be clear if people who undergo multiple rounds of testing (for instance because they suspected they were infected in March, and then again in September) are counted per round of testing, or only once.
Some countries report tests performed, while others report the number of individuals tested. The reason for this is that it is common for COVID-19 testing that the same person is tested more than once. The number of tests performed is different from the number of individuals tested. For citizens to trust and understand the published data, and for epidemiologists to incorporate the data into the models that inform public policy, it is crucial that every country provides the data on testing in a clearly documented way.ģ) Do numbers refer to ‘performed tests’ or ‘individuals tested’? It’s critical that governments provide a detailed and explicit account of the technologies that are being implemented as they get rolled out, disaggregating the test results accordingly. There are many different technologies for COVID-19 testing, some of which are already implemented, some currently available but not yet rolled out, and some still in development. As we discuss here, these different tests are used with different objectives in mind, and there are technical differences in how results from these different testing technologies should be interpreted. The available data is often not easy to find, because some countries are releasing figures at unpredictable intervals in ad-hoc locations (including social media or press conferences).Ģ) What testing technologies are being used? The first question to ask, then, is if there is any testing data for a given country.Įqually important is to make the available data findable. Many countries do not provide official figures.
Testing figures typically only include laboratory tests, and positive laboratory tests are usually still required to confirm cases of COVID-19 the interpretation of the positive rate could therefore be affected.ġ) Is there no data – or it is just hard to find? Case confirmation is generally based on a positive result from a PCR test and/or an antigen test, so including antibody tests in our figures would mean they were less useful for this purpose.Īt-home self-tests are widely available in many countries. Those that test for the presence of antibodies, aiming to establish whether an individual has been infected at some point in the past.Ĭurrently, we aim to include only PCR and antigen tests in our testing dataset, as our focus is on using testing data to help properly interpret the data we have on confirmed cases and deaths.3 Rapid antigen tests have also become commonly used in many countries, especially for the purpose of mass testing. The most common way of performing a test of the first type is with a PCR (polymerase chain reaction) test. Those that test for the presence of the virus, aiming to establish whether an individual is currently infected.There are many technologies for COVID-19 testing, some currently available and some still in development.īroadly, we can divide these different tests into two kinds:
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