Table 2.

Performance Characteristics of Twinkling Artifact and B-Mode Ultrasonography Overall and Stratified by Stone Size

	Sensitivity	Specificity	PPV	NPV	Correctly classified	Area under the curve
B-mode ultrasonography
<5 mm stones	52%	48%	25%	75%	49%	0.500
5–10 mm stones	73%	48%	15%	93%	51%	0.605
>10 mm stones	89%	48%	36%	93%	58%	0.688
Overall	71%	48%	52%	68%	58%	0.594
Twinkling artifact
<5 mm stones	36%	74%	30%	78%	64%	0.546
5–10 mm stones	36%	74%	15%	90%	69%	0.550
>10 mm stones	83%	74%	51%	93%	76%	0.782
Overall	56%	74%	62%	68%	66%	0.647

PPV=positive predictive value; NPV=negative predictive value.