TABLE 2.

Performance characteristics determined using a colonization index value of >0.5 and a corrected colonization index value of ≥0.3 (derived from culture results only; entire patient cohort included)

Variablea	n	RRb	P value	95% confidence interval (low)	95% confidence interval (high)	Sensitivity (%)	Specificity (%)	PPVc (%)	NPVd (%)
Time point 1 (n studied = 6,015)
At least 2 sites colonized (CIe ≥ 0.5)	1,671	2.25	0.0005	1.4	3.5	48	71	2	99
All 3 sites colonized	342	2.25	0.016	1.16	4.34	14	94	3	99
At least one site heavy density (CCIf ≥ 0.3)	1,549	3.7	<0.0001	2.36	5.93	58	74	3	99
At least 2 sites heavy density	448	3.1	0.001	1.77	5.4	21	92	3	99
At least throat heavy density	1,025	3.77	<0.0001	2.39	5.94	45	82	3	99
At least perineum heavy density	703	2	0.01	1.15	3.46	22	88	2	99
At least urine heavy density	327		NSg
Time point 2 (n studied = 3,244)
At least 2 sites colonized (CI ≥ 0.5)	1,056	2.4	0.002	1.38	4.16	54	67	3	99
All 3 sites colonized	238		NS
At least one site heavy density (CCI ≥ 0.3)	915	3.24	<0.0001	1.86	5.63	56	72	3	99
At least 2 sites heavy density	287	2.9	0.001	1.5	5.6	22	91	4	99
At least throat heavy density	530	3.93	<0.0001	2.26	6.81	44	84	4	99
At least perineum heavy density	481		NS
At least urine heavy density	233		NS
Time point 3 (n studied = 1,820)
At least 2 sites colonized (CI ≥ 0.5)	596	3.12	0.003	1.47	6.62	61	67	3	99
All 3 sites colonized	122		NS
At least one site heavy density (CCI ≥ 0.3)	480	2.1	0.05	0.99	4.39	43	74	3	99
At least 2 sites heavy density	143		NS
At least throat heavy density	253	2.83	0.009	1.3	6.2	32	86	4	99
At least perineum heavy density	263		NS
At least urine heavy density	126		NS

^aTime point 1, days 3 to 4 post-ICU admission; time point 2, days 6 to 8 post-ICU admission; time point 3, days 9 to 11 post-ICU admission.

^bRR, relative risk.

^cPPV, positive predictive value.

^dNPV, negative predictive value.

^eCI, uncorrected colonization index.

^fCCI, corrected colonization index.

^gNS, not significant.