Table 3.
Diagnostic performance of the Carba-R assay stratified by carbapenemase gene
| Carbapenemase gene (No. of carbapenemase genes detected by the Carba-R assay) | CPO carriage by culture (%) | No. of specimens with the following results | % (95% confidence interval) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Total | TP | FP | TN* | FN | Sensitivity | Specificity | PPV | NPV | ||
| KPC (n = 11)**† | 3.0 | 406 | 10 | 1 | 393 | 2 | 83.3 (51.6–97.9) | 99.8 (98.6–100.0) | 90.9 (58.2–98.6) | 99.5 (98.2–99.9) |
| NDM (n = 4) | 0.2 | 406 | 1 | 3 | 402 | 0 | 100.0 (2.5–100.0) | 99.3 (97.9–99.8) | 21.3 (8.1–45.5) | 100.0 (99.1–100.0) |
| VIM (n = 1) | NA | 406 | 0 | 1 | 405 | 0 | NA | 99.8 (98.6–100.0) | NA | 100.0 (99.1–100.0) |
| IMP-1 (n = 13)**† | 0.5 | 406 | 2 | 11 | 393 | 0 | 100.0 (15.8–100.0) | 97.3 (95.2–98.6) | 15.6 (9.3–24.8) | 100.0 (99.1–100.0) |
| OXA-48 (n = 1)** | NA | 406 | 0 | 1 | 405 | 0 | NA | 99.8 (98.6–100.0) | NA | 100.0 (99.1–100.0) |
| Total (n = 28) | 3.7 | 406 | 15 | 13 | 378 | 0 | 100.0 (78.2–100.0) | 96.7 (94.4–98.2) | 53.6 (40.4–66.4) | 100.0 (99.0–100.0) |
*Specimens not detected by the Carba-R assay were considered as true negative results
**Two specimens were detected as KPC + IMP-1 and KPC + OXA-48
†The other two specimens were excluded because the results of PCR or CRE culture were not available.
Abbreviations: CPO carbapenemase-producing organism, TP true positive, FP false positive, TN true negative, FN false negative, PPV positive predictive value, NPV negative predictive value