TABLE 1.

Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of Case Definition of Noninvasive Infection due to Staphylococcus aureus from a Random Sample of Patients with S. aureus–Positive Culture Results from a Sample Obtained from a Nonsterile Body Site

Variable	Noninvasive infection due to S. aureus present according to reference standard		Predictive value (% [95% CI])
	Yes	No
Positive culture result and matching ICD-9-CM code	76	20	PPV, 76/96 (79.2 [70.0–86.1])
Positive culture result alone	18	80	NPV, 80/98 (81.6 [72.8–88.0])

NOTE. Reference standard as determined by means of medical chart review and application of the CDC/NHSN surveillance definitions for specific type of infection. Cases of noninvasive infection due to S. aureus that meet the criteria are those with a positive clinical culture result and a matching International Classification of Diseases, Ninth Revision (ICD-9-CM), code for infection (refer to Appendix 1 for list of codes) from a same-day outpatient encounter or associated hospitalization. Cases that do not meet the criteria are those with positive clinical culture result without ICD-9-CM code for infection. CI, confidence interval.