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Kaplan-Meier Survival Curve

Learn to build and use Kaplan-Meier Survival Curve charts in the Cohort Browser.
The Cohort Browser is accessible to all users of the UK Biobank Research Analysis Platform and the Our Future Health Trusted Research Environment.
For DNAnexus Platform users, an Apollo license is required to access the Cohort Browser. Contact DNAnexus Sales for more information.

Building a Kaplan-Meier Survival Curve Chart

To generate a survival chart, select one numerical field representing time, and one categorical field, which will be transformed into the individual’s status.
1x numerical
1x categorical
The categorical field should use one of the following 4 terms (case-insensitive) to indicate a status of "Living": “living”, “alive”, “diseasefree”, “disease-free”
For multi-entity datasets, survival curve charts only support data fields from the main entity, or entities with 1:1 relation to the main entity.

Calculating Survival Percentage

To calculate survival percent at the current event the system evaluates the following formula:
ST: Survival at the current event
LT0: Number of subjects living at the start of the period or event
D: Number of subjects that died
For each time period the following values are generated:
Status
  • Each individual is considered Dead unless they qualify as Living
Number of Subjects Living at the Start (LT0)
  • For the initial value this is the total number of records returned by the backend from survival data with Living or Dead Status.
  • For followup events this is the number of subjects at the start of the previous event minus the number of subjects that died in the previous event and the subjects that dropped out or were censored in the previous event
Number of Subjects Who Died (D)
  • 1 for each individual who at the event does not have a status of Living
Number of Subjects Dropped or Censored
  • 1 for each individual who at the event has a status of Living
Survival Percent at the Current Event (ST)
Cumulative Survival (S)
  • ST-1: Survival percent at the previous event
Note that this is the actual point drawn on the survival plot.

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