Table 4.

Test characteristics comparing appendix maximal outer diameter in patients with unequivocal ultrasound studies against secondary signs (SS) in patients with equivocal US.

Test Characteristics	Unequivocal patients (N=295)	Equivocal patients with at least 1 SS (N=530)	Equivocal patients with at least 2 SS (N=530)	Equivocal patients with at least 3 SS (N=530)	Hyperemia, fluid collection, or appendicolith present (N=530)
Sensitivity	95.7%	48.7%	25.7%	12.2%	35.1%
Specificity	65.4%	89.5%	98.3%	99.3%	96.3%
PPV	83.0%	42.9%	70.4%	75.0%	60.5%
NPV	90.0%	89.5%	89.1%	87.5%	89.9%
Accuracy	84.7%	83.8%	88.1%	87.2%	87.7%