TABLE 3.
Sensitivities, specificities, positive predictive values, and negative predictive values of the various combination tests and DDSTs evaluated for the phenotypic detection of ESBLs in 155 KPC-producing isolatesa
| ESBL screening method | No. (%) of isolates confirmed by PCR to be: |
Test performance (%) |
||||
|---|---|---|---|---|---|---|
| ESBL-producing isolates (n = 118) | Non-ESBL-producing isolates (n = 37) | Sensitivity | Specificity | PPV | NPV | |
| CTX-CA vs CTX and/or CAZ-CA vs CAZ | 79 (66.9) | 0 (0) | 66.9 | 100 | 100 | 48.7 |
| CTX-CA-ΒΑ vs CTX-ΒΑ and/or CAZ-CA-ΒΑ vs CAZ-ΒΑ | 118 (100) | 0 (0) | 100 | 100 | 100 | 100 |
| DDST,b ATM, CAZ, CTX, or FEP 20 mm from AMC | 8 (6.8) | 0 (0) | 6.8 | 100 | 100 | 25.2 |
| DDST,b ATM-BA, CAZ-BA, CTX-BA, or FEP-BA 30 mm from AMC-BA | 28 (23.7) | 0 (0) | 23.7 | 100 | 100 | 29.1 |
| DDST,b ATM-BA, CAZ-BA, CTX-BA, or FEP-BA 25 mm from AMC-BA | 101 (85.6) | 0 (0) | 85.6 | 100 | 100 | 68.5 |
| DDST,b ATM-BA, CAZ-BA, CTX-BA, or FEP-BA 20 mm from AMC-BA | 116 (98.3) | 0 (0) | 98.3 | 100 | 100 | 94.9 |
a
Abbreviations: ATM, aztreonam; FEP, cefepime; PPV, positive predictive value, NPV, negative predictive value. All other abbreviations are defined in the text.
b
At least one combination.