Table 3. Optimal thresholds derived from Youden’s J Statistic.

Danger Level Combination	Optimal threshold (%)	Youden’s J	Sensitivity (%)	Specificity (%)
D4	1	0.257	36.5	89.9
D3+D4	2	0.464	83.2	63.2
D2+D3+D4	48	0.433	78.4	64.9