Table 3. Results of multivariate Poisson regression analysis for variation in the rate of breast-conserving surgery (BCS) and estimated rate ratios (RR) of BCS by hospital for each period of diagnosis (with 1989–1991 as reference).

			Time trend for BCS
			1989–1991	1992–1994	1995–1997	1998–2000	2001–2002
	RRa	95% CI	RR	RR	RR	RR	RR
Hospital
Hospital A	1.89	1.14–3.12	1.00	0.72	0.83	0.99	1.14
Hospital B	1.87	1.18–2.95	1.00	0.85	0.84	0.97	0.98
Hospital C	1.93	1.06–3.50	1.00	0.40	0.88	0.92	1.01
Hospital D	1.38	0.80–2.37	1.00	1.09	0.98	1.11	1.51
Hospital E	1.68	1.02–2.76	1.00	0.83	0.81	0.78	0.95
Hospital F	1.30	0.79–2.12	1.00	0.97	1.03	1.22	1.43
Hospital G	1.66	0.95–2.89	1.00	0.78	1.02	0.62	0.74
Hospital H	0.96	0.63–1.46	1.00	1.15	0.95	1.64	1.58
Hospital I	0.91	0.51–1.61	1.00	0.92	0.95	1.69	1.88
Hospital J	1.04	0.61–1.75	1.00	0.81	0.73	1.39	1.66
Hospital K	1.26	0.68–2.31	1.00	0.77	0.77	0.85	0.87
Hospital L	0.61	0.34–1.10	1.00	1.63	1.55	1.86	2.30
Hospital M	0.71	0.37–1.36	1.00	1.05	0.81	1.45	2.54
Hospital N	0.98	0.61–1.56	1.00	0.79	0.67	1.36	1.38
Hospital O	0.53	0.25–1.14	1.00	1.10	1.81	2.33	2.94
Hospital P	1.03	0.57–1.86	1.00	1.00	0.94	1.31	0.58
Hospital Q	1.63	0.80–3.32	1.00	0.52	0.52	0.56	0.71
Hospital R	0.61	0.31–1.17	1.00	1.23	0.88	2.19	1.46
Hospital S	0.58	0.26–1.27	1.00	1.00	1.02	1.38	1.06

^aRelative risk of BCS for the period 1989–1991 vs the regional average BCS rate, adjusted for age, tumour size, period of diagnosis, histology, location and mode of detection.

95% CI: 95% confidence interval for RR.