Check if rare outcome assumption is violated

Check if rare outcome assumption is violated

Usage

checkRareOutcomeAssumption(
  studyPopulation,
  firstOutcomeOnly = NULL,
  maxPrevalence = 0.1
)

Arguments

studyPopulation

An object created using the createStudyPopulation() function.

firstOutcomeOnly

Was the analysis restricted to the first outcome only? If left at NULL, will be determined by whether firstOutcomeOnly was set to TRUE when calling createStudyPopulation() or whether each person only had one outcome when pulling the data from the server.

maxPrevalence

The maximum allowed prevalence (proportion of people with the outcome) allowed when restricting to first outcome only.

Value

A tibble with one row and three columns: outcomeProportion indicates the proportion of people having the outcome at least once. firstOutcomeOnly indicated whether the analysis was restricted to the first outcome only. rare is TRUE if the rare outcome assumption is met, or the analysis was not restricted to the first outcome.

Details

Most SCCS analyses restrict to the first outcome occurrence per person to avoid violating the assumption that subsequent occurrences are independent. This is fine, as long as the outcome is rare. According to Farrington et al., the magnitude of the bias from violating this assumption is 0.5p, where p is the prevalence. By default we set the threshold for p at 0.1, corresponding to at most 5 percent bias.

The prevalence was computed in the getDbSccsData() function, within the population defined by the observation_period table, and restricted to the study period(s) and nesting cohort if used.

References

Farrington P, Whitaker H, Ghebremichael-Weldeselassie Y, Self-Controlled Case Series Studies: A Modelling Guide with R, CRC Press, 2018