Table 3.

Association between age and peritonitis rate for each organism category by era

	1996 to 2000 (695 incident patients with 1517 peritonitis episodes)			2001 to 2005 (910 incident patients with 1541 peritonitis episodes)
Category	Rate ratio (per decade increase in age)	95% CI	P	Rate ratio (per decade increase in age)	95% CI	P
Gram positive	1.06	0.99 to 1.13	0.098	1.04	0.98 to 1.11	0.22
Gram negative	1.11	0.96 to 1.29	0.17	0.97	0.87 to 1.07	0.54
Culture negative	0.96	0.85 to 1.09	0.55	1.00	0.89 to 1.12	0.98
CNS	1.09	0.99 to 1.19	0.084	1.06	0.97 to 1.16	0.20
S. aureus	1.05	0.86 to 1.29	0.62	0.84	0.68 to 1.03	0.096
Streptococcus	0.90	0.78 to 1.04	0.14	1.08	0.94 to 1.24	0.26
Pseudomonas	1.05	0.97 to 1.14	0.21	1.00	0.92 to 1.10	0.93
E. coli	1.37	1.07 to 1.74	0.011	0.94	0.74 to 1.18	0.58
Yeast	1.09	0.93 to 1.28	0.30	1.05	0.93 to 1.18	0.46

CNS, coagulase negative staphylococcus; CI, confidence interval.