TABLE 1.
Accuracy of 11 phenotypic assays for carbapenemase detection using 96 carbapenem-resistant non-glucose-fermenting isolates
| Assay | No. of positive tests/no. of isolates producing the specific carbapenemase (% positive) |
% sensitivity (95% confidence interval) for all CPNF (n = 28) | % specificity (95% confidence interval) for non-CPNF (n = 68) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Class A | Class B |
Class D |
|||||||||||||
| KPC (n = 2) | NDM (n = 4) | VIM (n = 8) | IMP (n = 3) | SPM (n = 1) | All class B (n = 16) | OXA-23 (n = 3) | OXA-58 (n = 1) | OXA-72 (n = 1) | OXA-23 + NDM (n = 1) | OXA-23 + OXA-24 (n = 1) | OXA-24 (n = 3) | All OXA types (n = 10) | |||
| Rapidec Carba NP | 2/2 (100) | 4/4 (100) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 16/16 (100) | 3/3 (100) | 1/1 (100) | 0/1 (0) | 1/1 (100) | 1/1 (100) | 0/3 (0) | 8/10 (80) | 93 (75–99) | 87 (76–93) |
| Neo-Rapid Carb Screen | 2/2 (100) | 4/4 (100) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 16/16 (100) | 3/3 (100) | 1/1 (100) | 1/1 (100) | 1/1 (100) | 0/1 (0) | 3/3 (100) | 8/10 (80) | 93 (75–99) | 99 (91–100) |
| Rapid CARB Blue Screen | 2/2 (100) | 4/4 (100) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 16/16 (100) | 1/3 (33) | 1/1 (100) | 0/1 (0) | 1/1 (100) | 1/1 (100) | 0/3 (0) | 4/10 (40) | 79 (59–91) | 99 (91–100) |
| Manual Carba NP CLSI | 2/2 (100) | 3/4 (75) | 7/8 (88) | 3/3 (100) | 1/1 (100) | 14/16 (88) | 0/3 (0) | 0/1 (0) | 0/1 (0) | 0/1 (0) | 0/1 (0) | 0/3 (0) | 0/10 (0) | 57 (37–75) | 99 (91–100) |
| Manual Blue Carba | 2/2 (100) | 4/4 (100) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 16/16 (100) | 2/3 (67) | 1/1 (100) | 0/1 (0) | 1/1 (100) | 0/1 (0) | 0/3 (0) | 4/10 (40) | 79 (14–73) | 76 (64–86) |
| Modified Carba NP | 2/2 (100) | 4/4 (100) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 16/16 (100) | 2/3 (67) | 1/1 (100) | 1/1 (100) | 1/1 (100) | 1/1 (100) | 0/3 (0) | 7/10 (70) | 89 (71–97) | 62 (49–73) |
| Boronic acid synergy test | 1/2 (50) | 68 (58–77) | |||||||||||||
| Metallo-β-lactamase Etest | 4/4 (100) | 7/8 (88) | 1/3 (33) | 1/1 (100) | 13/16 (81) | 0/1 (0) | 76 (50–92) | 87 (78–93) | |||||||
| Modified Hodge test | 2/2 (100) | 2/4 (50) | 3/8 (38) | 3/3 (100) | 1/1 (100) | 9/16 (56) | 1/3 (33) | 1/1 (100) | 1/1 (100) | 1/1 (100) | 1/1 (100) | 3/3 (100) | 8/10 (80) | 68 (48–83) | 91 (81–96) |
| Carbapenem inactivation method | 2/2 (100) | 0/4 (0) | 5/8 (63) | 3/3 (100) | 1/1 (100) | 9/16 (56) | 1/3 (33) | 0/1 (0) | 1/1 (100) | 0/1 (0) | 1/1 (100) | 0/3 (0) | 4/10 (40) | 54 (34–72) | 96 (87–99) |
| Modified carbapenem inactivation method | 2/2 (100) | 3/4 (75) | 8/8 (100) | 3/3 (100) | 1/1 (100) | 15/16 (94) | 2/3 (67) | 1/1 (100) | 1/1 (100) | 0/1 (0) | 1/1 (100) | 3/3 (100) | 7/10 (70) | 86 (66–95) | 92 (82–97) |