TABLE 3.
Number of imipenem and meropenem errors among 95 Enterobacteriaceae isolates in the accuracy of test methods study
| Parameter | Imipenema
|
Meropenemb
|
||||||
|---|---|---|---|---|---|---|---|---|
| Category agreement
|
% Overall essential agreement (evaluable)f | Category agreement
|
% Overall essential agreement (evaluable)f | |||||
| No. of very major errorsc | No. of major errors (%)d | No. of minor errors (%)e | No. of very major errorsc | No. of major errors (%)d | No. of minor errors (%)e | |||
| Agar dilution | 91.6 (88.7) | 98.9 (71.4) | ||||||
| Initial test | 0 | 0 | 6 (6.3) | 1g | 0 | 1 (1.1) | ||
| No. unresolvedh | 0 | 0 | 1g | 0 | ||||
| Outside ± 1 dilutioni | 2 (2.1) | 0 | ||||||
| Disk diffusion | N/Aj | N/A | ||||||
| Initial test | 1 | 0 | 5 (5.3) | 1g | 2 (2.3) | 4 (4.2) | ||
| No. unresolved | 1 | 0 | 1g | 2 (2.3) | ||||
| Outside 3 mmk | 1 (1.1) | 0 | ||||||
| Etest | 87.4 (84.0) | 93.7 (56.3) | ||||||
| Initial Test | 0 | 0 | 5 (5.3) | 1g | 0 | 1 (1.1) | ||
| No. unresolved | 0 | 0 | 1g | 0 | ||||
| Outside ± 1 dilution | 3 (3.2) | 0 | ||||||
| MicroScan Combo | NDl | ND | ||||||
| Initial test | 0 | 1 (1.2) | 8 (8.4) | 2g | 0 | 2 (2.1) | ||
| No. unresolved | 0 | 0 | 1 | 0 | ||||
| MicroScan MIC | 93.7 (91.4) | ND | ||||||
| Initial test | 0 | 1 (1.2) | 8 (8.4) | 1g | 0 | 3 (3.2) | ||
| No. unresolved | 0 | 0 | 0 | 0 | ||||
| Vitek | ND | ND | ||||||
| Initial test | 1 | 1 (1.2) | 5 (5.3) | 2g | 0 | 4 (4.2) | ||
| No. unresolved | 1 | 1 (1.2) | 2g | 0 | ||||
Test results were compared to BMD results. By BMD testing, seven isolates were imipenem resistant and 84 were imipenem susceptible.
Test results were compared to BMD results. By BMD testing, five isolates were meropenem resistant and 88 were meropenem susceptible.
The very major error rate could not be established due to low numbers of carbapenem-resistant isolates.
Major error rate = (number of major errors/total number of carbapenem-susceptible isolates) × 100.
Minor error rate = (number of minor errors/total number of isolates tested) × 100.
Essential agreement = number of test method MICs within one dilution of the reference/total number of results. Only on-scale results are included in the evaluable-result calculation.
One error resulted from testing of the same S. marcescens isolate.
Number of very major or major errors persisting upon repeat testing.
Number of minor errors >1 dilution from the BMD MIC.
N/A, not applicable. Essential agreement calculations apply only to testing methods that generate MIC results.
Number of minor errors >3 mm from the categorical disk diffusion breakpoint corresponding to the BMD MIC breakpoint.
ND, not done. Valid essential agreement calculations require that the test panels and cards contain at least five twofold dilutions of the evaluated antimicrobial agent.