How to determine the end of the follow-up period, I do not understand how the end of the follow-up period similar to September 30, 2021 mentioned in many articles is obtained.

alex

 Many articles mention the end of follow-up time or censor time, such as PMID: 38950855（Reproductive factors, genetic susceptibility and risk of type 2 diabetes: A prospective cohort study）, which is obviously not the time mentioned by the Field ID p53 variable.  I want to know what website or which variable can get the time, this question has puzzled me for a long time. 

The outcome of this study was incident T2DM, which was determined using the International Classification of Diseases (ICD-10) code E11. Prevalent diabetes was determined using the modified UK Biobank algorithms developed previously [33]. The detailed definitions are provided in Table S1 (see supplementary materials associated with this article on line). Participants were followed from recruitment until the occurrence of incident T2DM, death, loss of follow-up, or the end of the follow-up period (September 30, 2021), whichever came first.

 

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    Laura B Data Analyst

    Hi Alex,

    Thanks for your question! As you note, Data-Field 53 doesn’t refer to censoring date; it is simply the date at which a participant last attended an assessment centre. Since outcomes are followed up by linkage to participants’ health records from the NHS, we will often have linkage data for them from after their most recent assessment (particularly since most participants only attended baseline). 

    For censoring dates for linkage data, you can look at the Data providers and dates of data availability page which gives the current suggested censoring dates for each type of linked health data. Censoring dates are estimated as “the last day of the month for which the number of records is greater than 90% of the mean of the number of records for the previous three months, except where the data for that month is known to be incomplete in which case the censoring date is the last day of the previous month.” 

    For the algorithm used for a particular piece of research, you would need to get in touch with the authors, if it’s not clear from the article itself. Regarding the date of September 30, 2021, this may refer to the most recent refresh of the Data Showcase before the authors finalised their dataset for analysis and publication, but I am not sure. Please note that this method may not provide an accurate censoring date for health outcomes follow-up, as linkage datasets are generally received well before the date that the Showcase is refreshed.

    Researchers should make sure to decide how to estimate censoring dates appropriately based on their own protocol, but following feedback from our Epidemiology team, you might want to consider using the earliest of the following to determine clinical outcome and censoring dates in analysis:

    • Date of outcome of interest (outcome-specific, e.g. field 40005 for cancer outcomes)
    • Date of death (field 40000)
    • Date lost to follow-up (field 191) – Please be aware that these are out of date; we’re planning to update them in future but currently aren't able to provide a timeline for this. Once a release date has been determined it will be published on the future timelines page of the website.
    • Censoring date of linked healthcare records (outcome-specific, refer to Data providers and dates of data availability)
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