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Table 3 Diagnostic performance of the Carba-R assay stratified by carbapenemase gene

From: Diagnostic performance of the Xpert Carba-R assay for active surveillance of rectal carbapenemase-producing organisms in intensive care unit patients

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)

  1. *Specimens not detected by the Carba-R assay were considered as true negative results
  2. **Two specimens were detected as KPC + IMP-1 and KPC + OXA-48
  3. †The other two specimens were excluded because the results of PCR or CRE culture were not available.
  4. 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