TABLE 3.

Sensitivity, specificity, and positive and negative predictive values of the Xpert MRSA kit compared with those from direct and enrichment cultures from nose, throat, and groin/perineum specimens

Reference method and analysis group	Sited	Value (%) of Xpert MRSA kit
		Sensitivity	Specificity	PPVe	NPVf
Direct culture	All	88	92	53	99
Enrichment culture	All	79	94	71	96
	Nose	84	92	67	97
	Throat	63	98	83	93
	Groin/perineum	92	94	69	99
Amended resultsa
All patients	All	90	97	86	98
	Nose	95	98	90	99
	Throat	75	98	88	96
	Groin/perineum	97	96	80	99
Previously positive patientsb	All	87	100	100	87
	Nose	93	100	100	88
	Throat	73	100	100	77
	Groin/perineum	95	100	100	96
Patients who were not previously positivec	All	96	97	62	100
	Nose	100	97	67	100
	Throat	83	98	63	99
	Groin/perineum	100	95	59	100

^aFor further explanation of amended results, see Table 2, footnote c.

^bAnalysis restricted to specimens from patients who were previously MRSA positive. With these specimens, kit-positive culture-negative specimens were also included as true positives because the patients were known to have been previously positive for MRSA.

^cAnalysis restricted to specimens from patients with no record of being previously MRSA positive. With these specimens, kit-positive culture-negative specimens were also included as true positives if the patient was positive for MRSA at another site.

^dAll, nose, throat, and groin/perineum.

^ePPV, positive predictive value.

^fNPV, negative predictive value.