Table 4:

Model performance stratified by adverse event occurrence

Outcome	Selection rule	Population % flagged	Yield	NPV
ED	Any trigger	57%	10.3%	99.4%
	4+ Triggers	11.8%	17.2%	96.9%
	9+ Triggers	1%	34.8%	94.7%
	Lasso-10	10%	23.1%	96.9%
	Lasso-1	1%	51.7%	92.3%
POA	Any trigger	27.3%	17.5%	93.6%
	2+ Triggers	6.7%	31.4%	92.2%
	3+ Triggers	1.3%	47.4%	90.1%
	Lasso-10	10%	27.3%	92.9%
	Lasso-1	1%	54.1%	90.9%

Performance of the ED Trigger Tool to detect adverse events, by AE type: occurring in the ED or present on arrival (POA). Selection rule: Different sets of triggers are used for each outcome (Table 2 and Table S2): ED (up to 30 triggers), POA (up to 9). For ED events, “9+ Triggers” implies that only visits with 9 or more of the 30 triggers are eligible for review. LASSO scores are calculated using outcome-specific models and triggers (weights in Tables 2 and S2). Population: the proportion of all visits that would be marked as eligible for review by each selection rule. A randomly selected subset of these would then be selected for actual reviews. LASSO scores were thresholded to return visits with either the top 10% (Lasso-10) or top 1% (Lasso-1) of risk scores in the population. The cutoffs for the numbers of triggers were selected to yield as close to 10% or 1% as possible. Yield: for each outcome and each selection rule, the % of records expected to have an AE of that type (ED or POA). NPV: (negative predictive value) the % of unselected records that do not have AEs. The drop in NPV with more restrictive selection reflects the known trade-off between sensitivity and specificity.