Table 1

Flowchart of procedures included in the original PRAIS-2 validation and the current study

	PRAIS-2 national sample	Bristol cohort
April 2004–March 2009	None	n=1352 Fully independent validation Cohort 1 and exploration of temporal calibration drift
April 2009–March 2014	n=21 838 Original training	n=1515 Geographical and temporal calibration drift, Overlapping Cohort
April 2014–March 2015	n=4207 Original external validation	n=309 Combined with 1515 above for geographical and temporal calibration drift, Overlapping Cohort
April 2015–July 2019	None	n=1197 Fully independent validation Cohort 2 and exploration of temporal calibration drift (with priority data)
April 2015–July 2019	None	Elective n=714	Non-elective=483 First exploration of whether PRAIS-2 accurately stratifies non-elective procedures