TABLE 4.

Statistical analysis of the different phenotypic tests used to differentiate carbapenemase-producing K. pneumoniae isolates (n = 42) from non-carbapenemase producers (n = 103)^a

Method	Interpretative criteria	Sensitivity (%)b				Specificity (%)b
		IPM	MEM	ERT	DOR	IPM	MEM	ERT	DOR
BMD	Original CLSI/FDA criteriac	100	100	100	100	92.0	89.6	83.1	83.7
	Updated 2010 CLSI criteriad	100	100	100	100	86.6	86.6	76.3	85.1
Etest	Original CLSI/FDA criteriac	100	100	100	97.7	95.4	92.8	84.4	85.1
	Updated 2010 CLSI criteriad	80.8	91.3	97.7	95.5	88.8	85.8	77.4	88.8
DD	Original CLSI/FDA criteriac	NA	100	100	100	NA	87.3	82.4	84.4
	Updated 2010 CLSI criteriad	100	100	100	100	90.4	84.4	77.4	84.4
MHT alonee	NA	100	100	NA	NA	88.0	91.2	NA	NA

^aBMD, broth microdilution; MHT, modified Hodge test; DD, disk diffusion; IPM, imipenem; MEM, meropenem; ERT, ertapenem; DOR, doripenem.

^bSensitivity = TP/(TP + FN); specificity = TN/(TN+FP). TP, number of carbapenemase producers (n = 42); TN, number of non-carbapenemase producers (n = 103); TP, number of true positive results; TN, number of true negative results; FP, number of false-positive results; FN, number of false-negative results.

^cBased on original CLSI criteria for IPM, MEM, and ERT, with MHT performed with meropenem, and on FDA criteria for DOR (see Table 1).

^dBased on updated CLSI criteria (see Table 2).

^eAbility of MHT performed on all strains (n = 145), using IPM and MEM disks, to identify carbapenemase-producing isolates correctly.