Table 2.
Performance of the illumigene group A Streptococcus assay compared to that of the extracted culture
| Clinical test site no. | No. | Result (no.)a |
Performance (% [95% CI])b |
||||||
|---|---|---|---|---|---|---|---|---|---|
| TP | FP | TN | FN | Sensitivity | Specificity | PPV | NPV | ||
| 1 | 338 | 47 | 4 | 287 | 0 | 100 (92–100) | 98.6 (96–99) | 92.2 (81–97) | 100 (98–100) |
| 2 | 241 | 28 | 8 | 203 | 2 | 93.3 (77–99) | 96.2 (92–98) | 77.8 (60–89) | 99 (96–99) |
| 3 | 217 | 25 | 4 | 188 | 0 | 100 (86–100) | 97.9 (94–99) | 86.2 (68–96) | 100 (98–100) |
| Total | 796 | 100 | 16c | 678 | 2d | 98.0 (93–99) | 97.7 (96–98) | 86.2 (78–91) | 99.7 (98–99) |
a
TP, true positive; FP, false positive; TN, true negative; FN, false negative.
b
CI, confidence interval; PPV, positive predictive value; NPV, negative predictive value.
c
Thirteen of 16 specimens were positive for GAS using an alternative molecular assay.
d
One of 2 specimens was negative for GAS using an alternative molecular assay.