How to get the specific dates corresponding to different instances of the same field for each participant?
Let's take BMI as an example, each participant's BMI has four instances from 0 to 3. I want to know the exact date when each instance was recorded. does the UK biobank database provide the corresponding dates? If so, how do I get the corresponding date for each instance?
Another question, is the same instance for different fields (BMI | Instance 0 and Platelet count | Instance 0) recorded on the same day or on different dates?
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Hi Alex,
the BMI in field 21001 is derived from height and weight measurements taken at UKB assessment centre visits. The dates of these visits are in field 53.
For most of the UKB fields, “instance” means “assessment centre visit”. There are a few fields, such as the online questionnaire results and the accelerometry data, where “instance” has a different meaning. To find the correct meaning of “instance” for each field, please see the Showcase field page where it says “instancing N”
and the linked instance description, for example https://biobank.ndph.ox.ac.uk/showcase/instance.cgi?id=2 . For a comprehensive list, see Schema 9 .
For more on Instances and Arrays, see this Article .
Platelet count in field 30080 is also instancing 2, meaning assessment centre visit.
To find each field in Showcase, there is a link within the cohort browser column selection, or you can use Showcase search.
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