Are there any limitations to using a formula?

Yes there are. While using a formula to take into account the complexity of each child’s medical problems allows for fairer assessment of a hospital’s survival rate, it still cannot make it completely fair. There will always be information about important factors that affect a child’s chances of survival that are not routinely collected for national bodies and so cannot be captured by a formula that was developed using national data.

Any statistical formula has to be developed on existing data and so the data will be typically at least a year out of date. So risk adjustment cannot adjust or account for future changes to the way data is collected (for instance more complete data) or new methods of surgical or medical management. Often, these statistical formulas are updated every few years with more up to date information (in 2016, we updated the PRAiS statistical model for the third time).