TABLE 1.

Performance of the Shiga Toxin Direct test compared to routine culture and EIA^a

Organism and sample type	No. of TP	No. of FP	No. of TN	No. of FN	Sensitivity,b % (CI)	Specificity,c % (CI)	PPV, % (CI)	NPV, % (CI)
STEC
Fresh, prospective	4	8e	1,070	0	100 (40–100)	99.3 (98–100)	33.3 (11–65)	100 (99–100)
Frozen, retrospective	51	0	33	4f	92.7 (82–98)	100 (87–100)	100 (91–100)	89.2 (74–96)
Total	55	8	1,103	4	93.2 (83–98)	99.3 (99–100)	87.3 (76–94)	99.6 (99–100)
O:157d
Fresh, prospective	0	2g	4	0	ND	66.7 (24–94)	0 (0–80)	100 (99–100)
Frozen, retrospective	22	0	24	1h	95.7 (76–100)	100 (83–100)	100 (82–100)	96.0 (78–100)
Total	22	2	28	1	95.7 (76–100)	93.3 (76–99)	91.7 (72–99)	69.6 (80–100)

^aA total of 1,170 specimens were tested. Abbreviations: TP, true positives; FP, false positives; TN, true negatives; FN, false negatives; PPV, positive predictive value; NPV, negative predictive value; CI, 95% confidence interval.

^bPositive percent agreement for frozen, retrospective specimens.

^cNegative percent agreement for frozen, retrospective specimens.

^dO:157 result is reported only if specimens were positive for STEC.

^ePreserved stool specimens and enrichment broths were subjected to bidirectional sequence analysis (LOD ∼ 10⁴ CFU/ml). Sequence for stx₁, stx₂, or both was confirmed in all 8 samples.

^fAll 4 specimens were positive by alternative molecular IVD test but negative by bidirectional sequence analysis.

^gBoth specimens were reported as positive for E. coli O:157 by an alternative molecular IVD test.

^hSpecimen was reported as positive for serotype E. coli O:157 by an alternative molecular IVD test.