Coronadashboard data explained
- Coronadashboard data explained

Positive tests

Where do the numbers come from?

The figures on the number of positive tests are supplied by the National Institute for Public Health and the Environment (RIVM). RIVM also supplies the figures on the ages of people who have tested positive as open data.

How are the numbers calculated?

Number of positive tests
The figure shows the number of positive tests reported to RIVM in the preceding 24 hours, up to 10.00 on the day of publication of the figures. The date attributed to positive tests is the date on which RIVM was notified by the municipal health authority (GGD). This is not the same as the date on which people are tested. The data is organized based on the date the tests were conducted. On average it takes 1 to 2 days before test results are produced.

Doctors and laboratories are required to report cases of infectious disease to the GGD. However, coronavirus tests are also carried out by commercial organisations and individuals. The results of these tests are not always reported to the GGD, or the notification is not counted as the test used does not meet RIVM standards. Commercial testing organisations are required to report positive test results to the GGD. This means that the daily number of confirmed cases reported on the dashboard may not give the complete picture. This should be kept in mind when interpreting these figures.

The percentage of tests that have a positive result is based on tests conducted by the GGD and for which the results are known. The seven-day rolling average is calculated with a two-day delay. This is because the results of tests conducted in the last 48 hours may not yet be available. This way we can be sure that most of the results are available and that the percentage of positive tests is accurately represented.

Part of the notification process is done manually. Sometimes the GGDs will not have reported all newly confirmed cases at the moment that RIVM compiles the figures for the preceding 24 hours. Missing notifications are passed on at a later time. Missing or delayed notifications can skew the daily figures. The rolling average filters out this type of fluctuation, and therefore often gives a better picture of the number of infections.

Positive tests per age group over time
The figures on ages of positively tested persons come from a different data source than the figures on positive tests, because the dataset on positive tests does not contain ages. Different dates are used in the two datasets.

The dates used in the age file are:

  • the first day of illness
  • if this is not known: the day of the (first) positive laboratory result
  • if that is not known either: the day on which the GGD received the report

The file on positive tests uses the date of notification by RIVM. This date is usually further in the future per positive test result than the dates in the file with the ages. In addition, there are positive test results from people whose age is unknown. There are therefore differences between the graph for the absolute number of positively tested persons and the graph with the ages of positively tested persons.

The graph shows averages over the last 7 days. To be able to compare age groups, we calculate numbers per 100,000 people.

Growth rate
The growth rate (or G rate) is a percentage that expresses the change in the number of positive tests in the last 7 days relative to the number of positive tests in the preceding 7 days. To calculate the growth rate, data must be available for 14 consecutive days (the previous 7 days + the 7 days preceding that).

The growth rate is calculated by the Ministry of Health, Welfare and Sport based on data from RIVM. All historical growth rates are recalculated daily, so that any corrections made by RIVM to the number of positive tests are incorporated into the historical trend of the growth rate. The growth rate is calculated in line with the method used by research institute IPSE Studies. The growth rate was introduced by the Dutch newspaper de Volkskrant.

Adjustments and corrections

Closure of GGD test lanes

The coronavirus has reached an endemic phase and the GGD test streets will be closed as of 17 March 2023. As a result, the data will no longer be updated from 4 April 2023. The page Positive tests is archived.

Adjustments RIVM can also retrospectively correct data that has already been published. These corrections are processed in the open data file and incorporated into the dashboard. The data file registers cases at safety region and municipality level. In order to calculate data at national level we add all notified cases together. Some notified cases cannot be linked to a particular municipality/safety region, as this information is missing from the data file. These cases cannot therefore be shown at those levels, but they are included in the national figures.

11 April 2022
As of 11 April 2022, everyone no longer has to go to the GGD for a confirmation test. Target groups that can be tested include healthcare workers and residents of nursing homes. As a result, after April 11, 2022, the number of testers who go to the GGD after a positive self-test will be lower.

7 September 2021
On 7 September 2021, we added an additional notification in the graph "Percentage of GGD positive test results, over time". The percentage of positive tests is no longer clear and unambiguous to interpret and compare over time. This is partly due to a recent increase in testing at walk-in test sites not requiring an appointment for students during introduction weeks, testing of returning travellers, and testing for confirmation after a positive self-test.

1 July 2021
As of 1 July 2021 people who are planning to travel abroad can also be tested at GGD test centres. Before 10 August these people’s test results were included in the same data set as the results of people being tested by the GGD for other reasons. As of 10 August travellers’ test results are no longer included. Around 200,000 test results have been removed from the data set. The figures on the dashboard for the period between 1 July and 10 August have been adjusted accordingly. As a result, the percentage of positive test results in that period is higher than previously indicated. The increase is 2 to 3 percentage points, depending on the day.