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Cohort tables

Cohort table

A cohort is a set of people that fulfill a certain set of criteria for a period of time.

In omopgenerics we defined the cohort_table class that allows us to represent individuals in a cohort.

A cohort_table is created using the newCohortTable() function that is defined by:

Let’s start by creating a cdm reference with just two people.

person <- tibble(
  person_id = c(1,2),
  gender_concept_id = 0, year_of_birth = 1990,
  race_concept_id = 0, ethnicity_concept_id = 0
)
observation_period <- dplyr::tibble(
  observation_period_id = c(1,2), person_id = c(1,2),
  observation_period_start_date = as.Date("2000-01-01"),
  observation_period_end_date = as.Date("2021-12-31"),
  period_type_concept_id = 0
)
cdm <- cdmFromTables(
  tables = list(
    "person" = person,
    "observation_period" = observation_period
  ),
  cdmName = "example_cdm"
)
#> Warning: ! 5 column in person do not match expected column type:
#> • `person_id` is numeric but expected integer
#> • `gender_concept_id` is numeric but expected integer
#> • `year_of_birth` is numeric but expected integer
#> • `race_concept_id` is numeric but expected integer
#> • `ethnicity_concept_id` is numeric but expected integer
#> Warning: ! 3 column in observation_period do not match expected column type:
#> • `observation_period_id` is numeric but expected integer
#> • `person_id` is numeric but expected integer
#> • `period_type_concept_id` is numeric but expected integer
cdm
#> 
#> ── # OMOP CDM reference (local) of example_cdm ─────────────────────────────────
#> • omop tables: person, observation_period
#> • cohort tables: -
#> • achilles tables: -
#> • other tables: -

Now let’s say one of these people have a clinical event of interest, we can include them in a cohort table which can then be used as part of an analysis.

cohort <- tibble(
  cohort_definition_id = 1, subject_id = 1,
  cohort_start_date = as.Date("2020-01-01"),
  cohort_end_date = as.Date("2020-01-10")
)
cdm <- insertTable(cdm = cdm, name = "cohort", table = cohort)
cdm$cohort <- newCohortTable(cdm$cohort)
#> Warning: ! 2 column in cohort do not match expected column type:
#> • `cohort_definition_id` is numeric but expected integer
#> • `subject_id` is numeric but expected integer

The cohort table will be associated with settings and attrition. As we didn’t specify these in newCohortTable() above they will have been automatically populated. You can access the cohort set of a cohort table using the function settings()

settings(cdm$cohort)
#> # A tibble: 1 × 2
#>   cohort_definition_id cohort_name
#>                  <int> <chr>      
#> 1                    1 cohort_1

Meanwhile, you can access the cohort attrition of a cohort table using the function attrition()

attrition(cdm$cohort)
#> # A tibble: 1 × 7
#>   cohort_definition_id number_records number_subjects reason_id reason          
#>                  <int>          <int>           <int>     <int> <chr>           
#> 1                    1              1               1         1 Initial qualify…
#> # ℹ 2 more variables: excluded_records <int>, excluded_subjects <int>

Cohort attrition table is also used to compute the number of counts that each cohort (ie from the last row of the attrition). It can be seen with the function cohortCount().

cohortCount(cdm$cohort)
#> # A tibble: 1 × 3
#>   cohort_definition_id number_records number_subjects
#>                  <int>          <int>           <int>
#> 1                    1              1               1

Note that because the cohort count is taken from the last row of attrition, if we make changes to a cohort we should then update attrition as we go. We can do this

cdm$cohort <- cdm$cohort |>
  filter(cohort_start_date == as.Date("2019-01-01")) |>
  compute(name = "cohort", temporary = FALSE) |>
  recordCohortAttrition("Require cohort start January 1st 2019")
#> Warning: ! 1 casted column in cohort (cohort_attrition) as do not match expected column
#>   type:
#> • `cohort_definition_id` from numeric to integer
#> Warning: ! 2 column in cohort do not match expected column type:
#> • `cohort_definition_id` is numeric but expected integer
#> • `subject_id` is numeric but expected integer
attrition(cdm$cohort)
#> # A tibble: 2 × 7
#>   cohort_definition_id number_records number_subjects reason_id reason          
#>                  <int>          <int>           <int>     <int> <chr>           
#> 1                    1              1               1         1 Initial qualify…
#> 2                    1              0               0         2 Require cohort …
#> # ℹ 2 more variables: excluded_records <int>, excluded_subjects <int>
cohortCount(cdm$cohort)
#> # A tibble: 1 × 3
#>   cohort_definition_id number_records number_subjects
#>                  <int>          <int>           <int>
#> 1                    1              0               0

An additional, optional, attribute keeps track of the concepts used to create the cohort. In this example we do not have a codelist associated with our cohort.

cohortCodelist(cdm$cohort, cohortId = 1, type = "index event")
#> Warning: No codelists found for the specified cohorts
#> 
#> ── 0 codelists ─────────────────────────────────────────────────────────────────

We could though associate our cohort with a codelist

cdm$cohort <- newCohortTable(cdm$cohort, 
                             cohortCodelistRef = dplyr::tibble(
                                 cohort_definition_id = c(1,1),
                                 codelist_name =c("disease X", "disease X"),
                                 concept_id = c(101,102),
                                 type = "index event"
                               ))
#> Warning: ! 2 casted column in cohort (cohort_codelist) as do not match expected column
#>   type:
#> • `cohort_definition_id` from numeric to integer
#> • `concept_id` from numeric to integer
#> Warning: ! 2 column in cohort do not match expected column type:
#> • `cohort_definition_id` is numeric but expected integer
#> • `subject_id` is numeric but expected integer
cohortCodelist(cdm$cohort, cohortId = 1, type = "index event")
#> 
#> ── 1 codelist ──────────────────────────────────────────────────────────────────
#> 
#> - disease X (2 codes)

Each one of the elements that define a cohort table have to fulfill certain criteria.

Cohort Set

A cohort set must be a table with:

Cohort Attrition

A cohort attrition must be a table with:

Cohort Codelist

A cohort codelist must be a table with:

Cohort Table

A cohort table must be a table with:

Combining generated cohort sets

You can bind two cohort tables using the method bind(). You can combine several cohort tables using this method. The only constrain is that cohort names must be unique across the different cohort tables. You have to provide a name for the new cohort table.

asthma <- tibble(
  cohort_definition_id = 1, subject_id = 1,
  cohort_start_date = as.Date("2020-01-01"),
  cohort_end_date = as.Date("2020-01-10")
)
cdm <- insertTable(cdm, name = "asthma", table = asthma)
cdm$asthma <- newCohortTable(cdm$asthma, 
                             cohortSetRef = tibble(cohort_definition_id = 1,
                                                   cohort_name = "asthma"))
#> Warning: ! 1 casted column in asthma (cohort_set) as do not match expected column type:
#> • `cohort_definition_id` from numeric to integer
#> Warning: ! 2 column in asthma do not match expected column type:
#> • `cohort_definition_id` is numeric but expected integer
#> • `subject_id` is numeric but expected integer

copd <- tibble(
  cohort_definition_id = 1, subject_id = 2,
  cohort_start_date = as.Date("2020-01-01"),
  cohort_end_date = as.Date("2020-01-10")
)
cdm <-  insertTable(cdm, name = "copd", table = copd)
cdm$copd <- newCohortTable(cdm$copd, 
                           cohortSetRef = tibble(cohort_definition_id = 1,
                                                   cohort_name = "copd"))
#> Warning: ! 1 casted column in copd (cohort_set) as do not match expected column type:
#> • `cohort_definition_id` from numeric to integer
#> Warning: ! 2 column in copd do not match expected column type:
#> • `cohort_definition_id` is numeric but expected integer
#> • `subject_id` is numeric but expected integer

cdm <- bind(cdm$asthma, 
            cdm$copd,
            name = "exposures")
#> Warning: ! 1 column in exposures do not match expected column type:
#> • `subject_id` is numeric but expected integer
cdm$exposures
#> # A tibble: 2 × 4
#>   cohort_definition_id subject_id cohort_start_date cohort_end_date
#> *                <int>      <dbl> <date>            <date>         
#> 1                    1          1 2020-01-01        2020-01-10     
#> 2                    2          2 2020-01-01        2020-01-10

settings(cdm$exposures)
#> # A tibble: 2 × 2
#>   cohort_definition_id cohort_name
#>                  <int> <chr>      
#> 1                    1 asthma     
#> 2                    2 copd
attrition(cdm$exposures)
#> # A tibble: 2 × 7
#>   cohort_definition_id number_records number_subjects reason_id reason          
#>                  <int>          <int>           <int>     <int> <chr>           
#> 1                    1              1               1         1 Initial qualify…
#> 2                    2              1               1         1 Initial qualify…
#> # ℹ 2 more variables: excluded_records <int>, excluded_subjects <int>
cohortCount(cdm$exposures)
#> # A tibble: 2 × 3
#>   cohort_definition_id number_records number_subjects
#>                  <int>          <int>           <int>
#> 1                    1              1               1
#> 2                    2              1               1

Export metadata about a cohort table

You can export the metadata of a cohort_table using the function: summary():

summary(cdm$exposures) |>
  glimpse()
#> Rows: 12
#> Columns: 13
#> $ result_id        <int> 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4
#> $ cdm_name         <chr> "example_cdm", "example_cdm", "example_cdm", "example…
#> $ group_name       <chr> "cohort_name", "cohort_name", "cohort_name", "cohort_…
#> $ group_level      <chr> "asthma", "asthma", "copd", "copd", "asthma", "asthma…
#> $ strata_name      <chr> "overall", "overall", "overall", "overall", "reason",…
#> $ strata_level     <chr> "overall", "overall", "overall", "overall", "Initial …
#> $ variable_name    <chr> "number_records", "number_subjects", "number_records"…
#> $ variable_level   <chr> NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA
#> $ estimate_name    <chr> "count", "count", "count", "count", "count", "count",…
#> $ estimate_type    <chr> "integer", "integer", "integer", "integer", "integer"…
#> $ estimate_value   <chr> "1", "1", "1", "1", "1", "1", "0", "0", "1", "1", "0"…
#> $ additional_name  <chr> "overall", "overall", "overall", "overall", "reason_i…
#> $ additional_level <chr> "overall", "overall", "overall", "overall", "1", "1",…

This will provide a summarised_result object with the metadata of the cohort (cohort set, cohort counts and cohort attrition).

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They may not be fully stable and should be used with caution. We make no claims about them.