Compute readmission and episodes of care.

readmission.R computes whether or not a patient associated with an episode of care was readmitted to a GEMINI hospital within a time window of interest. The default readmission time window is 7 or 30 days.

In line with CIHI guidelines, readmission calculations are based on episodes of care instead of individual encounters in order to avoid that linked transfers are counted as readmissions (also see documentation for episodes_of_care()). Specifically, an episode of care refers to all contiguous inpatient hospitalizations to any medical or intensive care service within the GEMINI network. Episodes involving inter-facility transfers are linked regardless of diagnosis. An acute care transfer is assumed to have occurred if either of the following criteria are met:

An admission to a medical or intensive care service at a GEMINI hospital within 7 hours after discharge from another GEMINI hospital, regardless of whether the transfer is coded
An admission to a medical or intensive care service at a GEMINI hospital within 7-12 hours after discharge from another GEMINI hospital, and at least 1 hospital has coded the transfer: Coded transfers are based on the DAD Institution From and Institution To fields

For episodes of care involving acute care transfers, readmissions are attributed to the last hospital from which the patient was discharged before readmission.

Usage

readmission(
  dbcon,
  elective_admit = TRUE,
  death = TRUE,
  MAID = FALSE,
  palliative = FALSE,
  chemo = FALSE,
  mental = FALSE,
  obstetric = FALSE,
  signout = FALSE,
  restricted_cohort = NULL,
  readm_win = c(7, 30)
)

Arguments

dbcon: (DBIConnection)
A database connection to any GEMINI database.
elective_admit: (logical)
If TRUE (default), elective episodes of care are not considered to be true readmissions, and are therefore removed from the numerator. Specifically, if the first encounter of the (n)th episode of care is elective (admit_category = 'L'), the (n-1)th episode of care is not considered to be followed by a readmission (readmit(n-1) = FALSE).
death: (logical)
If TRUE (default), episodes of care ending in in-hospital death are removed from the denominator. Specifically, if the (n)th episode of care ended in death, it is impossible for a patient to be readmitted, and therefore the episode of care is not considered in the readmission calculation (readmit(n) = NA).
MAID: (logical)
If TRUE (default): Episodes of care that involve MAID are not considered to be true readmissions, and are therefore removed from the numerator. Specifically, if any encounter of the (n)th episode of care involves MAID, the (n-1)th episode of care is not considered to be followed by a readmission (readmit(n-1) = FALSE). Note that episodes of care involving MAID end in death, however, they are NOT removed from the denominator unless the death flag is set to TRUE as well (recommended approach).
palliative: (logical)
If TRUE (default): Episodes of care involving palliative care are excluded from both the numerator and denominator. Specifically, episode of care with palliative care as a type-M diagnosis are not considered to be true readmissions (readmit(n-1) = FALSE). Additionally, similarly to death, palliative episodes of care cannot be followed by future readmission and are therefore excluded from the denominator (readmit(n) = NA)
chemo: (logical)
If TRUE (default): Episodes of care that involve chemotherapy are not considered to be true readmissions, and are therefore removed from the numerator. Specifically, if any encounter of the (n)th episode of care involves chemotherapy, the (n-1)th episode of care is not considered to be followed by a readmission (readmit(n-1) = FALSE).
mental: (logical)
If TRUE (default): Episodes of care for mental health are excluded from both the numerator and denominator. Specifically, episodes of care that fall under CIHI's Major Clinical Category (MCC) 17 are not considered to be true readmissions and are therefore removed from the numerator (readmit(n-1) = FALSE). Additionally, they are not considered to be acute care and are therefore not included in the readmission denominator (readmit(n) = NA)
obstetric: (logical)
If TRUE (default): Episodes of care that involve obstetric delivery are not considered to be true readmissions, and are therefore removed from the numerator. Specifically, if any encounter of the (n)th episode of care involves obstetric delivery, the (n-1)th episode of care is not considered to be followed by a readmission (readmit(n-1) = FALSE).
signout: (logical)
If TRUE (default), episodes of care where the last encounter was self sign-out/left against medical advice (LAMA) are removed from the denominator. Specifically, if the (n)th episode of care ended in self-signout/LAMA, it is not considered in the readmission calculation (readmit(n) = NA).
restricted_cohort: (data.frame or data.table)
User specified cohort that is a restricted subset of all encounters in DRM table "ipadmdad" (see GEMINI Data Repository Dictionary). Must contain genc_id as the identifier. Default is Null, which loads the entire "ipadmdad" table in the user-provided database (recommended approach).
readm_win: (integer | vector)
readmission window(s) of interest, in days (by default: readm_win = c(7,30) to calculate 7- & 30-day readmission)

Value

This function returns a data.table containing genc_id, AT_in_occurred, AT_out_occurred, epicare (see episodes_of_care()), readmit7 (default), and readmit30 (default). readmit7 and readmit30 are logical variables indicating whether or not an episode of care was followed by a readmission. Note that readmissions are attributed to the last encounter of each episode of care. Episodes of care where the last encounter has readmitX = NA have been removed from the denominator.

Note: If the very last encounter of an episode of care has a transfer-out coding (but the encounter associated with that transfer does not exist in the GEMINI database), the episode of care is excluded from the readmission denominator (readmit(n) = NA). This is to avoid inaccurate attribution of a potential readmission to the hospital associated with the intermediate (i.e., not the last) encounter of that episode of care.

Details

This function calls the episodes_of_care() function to link encounters with acute care transfers into episodes of care. When conducting readmission calculations using the function output, the number of encounters where readmission == TRUE is the numerator, and the number of eligible episodes of care (where readmission != NA) is the denominator. For example, 7-day readmission rate can be calculated by mean(readmit7, na.rm=TRUE), where readmit7 is the variable returned by the readmission() function. This function is designed to be consistent with CIHI guidelines for readmission calculations. Please carefully review this reference before applying the function for research purposes. Users may choose to deviate from the CIHI definition of readmission by setting any of the CIHI flags (see above) to FALSE.

Warning

Warnings are produced if

either the death or elective_admit flags are set to FALSE,
the input contains a user-specified restricted cohort, or
more than 25% of episodes of care are removed from the denominator due to the CIHI flags or buffer period.

References

CIHI readmission guidelines

Examples

if (FALSE) { # \dontrun{
drv <- dbDriver("PostgreSQL")
dbcon <- DBI::dbConnect(drv,
                        dbname = "db",
                        host = "domain_name.ca",
                        port = 1234,
                        user = getPass("Enter user:"),
                        password = getPass("password"))

## default readmission calculation (with elective = TRUE & death = TRUE by default)
readmission(dbcon)

## Readmission calculation following CIHI definition
readmission(dbcon, elective_admit = TRUE, death = TRUE, MAID = TRUE, palliative = TRUE,
                   chemo = TRUE, mental = TRUE, obstetric = TRUE, signout = TRUE)

} # }