Why does the number of participants not match between Showcase and the UKB-RAP?

There are two main reasons for a difference in participant counts for a field:

1. Showcase is regularly augmented with new data.

After being uploaded to Showcase, new data is added into the UK Biobank Research Analysis Platform (UKB-RAP) by our partners at DNAnexus as  part of a new UKB-RAP Data Release version. This results in a short lag before the UKB-RAP is updated. 

If the Version Date for the Field page in Showcase is later than the most recent UKB-RAP Version Date, then at least some of the data for that field is not yet available in the Main Copy in the UKB-RAP, and therefore cannot yet be dispensed into a researcher's UKB-RAP project. Researchers are notified once the data included in the most recent Showcase refresh becomes available on the UKB-RAP Main Copy.   

The dates of the UKB-RAP Versions can be found in the DNAnexus documentation Version page.

Data within a research group's UKB-RAP project reflects the data that was available within the UKB-RAP Main Copy at the time the UKB-RAP project was dispensed. The dispense date (YYYYMMDD format) is included in the name of the Dataset Record item in the project.  If the dispense date is earlier than the UKB-RAP Version date, then researchers can refresh the UKB-RAP project or dispense a new UKB-RAP project to receive the new data. If the dispense date for the project is later than the UKB-RAP Version date, the project will already include all data available within the UKB-RAP for the relevant application tier.   If this is the case, it will not be possible to refresh the project, and dispensing a new project will not get any extra data.

To keep up-to-date with upcoming releases please see our future data release timelines page.

     2. Each UK Biobank participant can withdraw consent to the use of their data at any time.

Since 2006 approximately 1,200 participants have withdrawn. When a participant withdraws, their data is removed from the UKB-RAP. However, the numbers listed on Showcase are only updated when there is a Showcase Refresh. The most recent refresh date can be found on the timelines page. This means that the numbers listed in Data Showcase are likely to be slightly different from the numbers available on the UKB-RAP. 

If neither of these reasons explains the difference, it would be necessary to check that the fields being compared are actually equivalent. Most fields on the UKB-RAP have a link to the equivalent Data Showcase page (this link can be found in the Cohort Browser when adding a column to a cohort). Most fields on the UKB-RAP have the same field number in Showcase.

The information in this article about missing data may also be relevant.

If you are still concerned, please contact us with precise details of which field(s) you are looking at.