Table 2.

Sensitivity and specificity per patient for single-mark and double-mark CAD true positive presentation

	Sensitivity (n=21)		Specificity (n=12)
Reader	Single-mark	Double-mark	Single-mark	Double-mark
1	9 43%	13 62%	11 92%	8 67%
2	17 81%	19 90%	9 75%	10 83%
3	17 81%	19 90%	10 83%	12 100%
4	13 62%	10 48%	11 92%	10 83%
Average	56/84 67% [44%, 86%]	61/84 73% [48%, 94%]	41/48 85% [65%, 100%]	40/48 83% [63%, 98%]

Numbers are patients (%). Patients had at most one polyp. Note that per patient and per polyp sensitivities are not necessarily identical because radiologists could miss the true polyp and instead inappropriately mark a false positive as a polyp, leading to a true positive patient and false negative polyp. The differences between single-mark and double-mark reads for individual readers and for the average reader were not statistically significant using bootstrap analysis. 95% confidence intervals for the average reader are from the MRMC analysis. The data for specificity include three normal cases that were identical on two readings; each reading was arbitrarily assigned to either the single-mark or double-mark groups. For the other nine normal cases, a pair of false positives was either matched (double-mark) or unmatched on the supine and prone scans based on location and CAD score to mimic the situation for the abnormal cases.