Table 2.

Subset of Thresholds in the Age‐Stratified Algorithm and Resulting Test Characteristics in Comparison With the Original Algorithm

	BA Z Score	PCA Z Score	Sensitivity	Specificity	PPV	NPV	χ2 P Value
	−0.5	−2	0.5	0.82	0.31	0.91	0.04
	−1	−0.5	0.6	0.63	0.21	0.91	0.19
	−1	−1	0.5	0.74	0.24	0.90	0.14
	−1	−1.5	0.5	0.79	0.28	0.91	0.11
Optimized algorithm	−1	−2	0.5	0.84	0.33	0.91	0.03
	−1	−2.5	0.4	0.85	0.31	0.90	0.07
	−1	−3	0.3	0.90	0.33	0.89	0.10
	−1.5	−2	0.4	0.84	0.29	0.90	0.10
	−2	−2	0.3	0.87	0.27	0.89	0.17
Old algorithm	NA	NA	0.5	0.79	0.28	0.91	0.05

The shaded row highlights the optimum threshold. BA indicates basilar artery; NPV, negative predictive value; PCA, posterior cerebral artery; and PPV, positive predictive value.