Table 2.

Models of standardized incidence ratios for bladder cancer by Poisson regression using cumulative o-toluidine exposure rank prediction with reference population rates^a (10year lag) in workers from a chemical manufacturing plant (n=1,875)

Parameter		SIR Estimateb	Std Error	Approx. 95% CI (Wald)c	Model deviance or chi square to remove variable
1	CaOut = exp(a0) × expt				-2ln(L) = 1106.686
	a0	0.9468	0.1474	0.65,1.24
2	CaOut = exp(a0+b1×rac0) × expt				-2ln(L) = 1106.346
	a0	0.9309	0.1508	0.64,1.23
	b1	0.451	0.723	−0.97,1.87
3	CaOut = exp(a0+b1×rac0+c1×dur) × expt				-2ln(L) = 1096.590
	a0	0.3499	0.2672	−0.17,0.87
	b1	0.595	0.7248	−0.83,2.02
	c1	0.0319	0.0102	0.012,0.052	9.8
4	CaOut = exp(a0+b1×rac0) × (1+c2×cumOTr) × expt				-2ln(L) = 1079.482
	a0	−0.323	0.4207	−1.15,0.50
	b1	0.5849	0.7233	−0.83,2.00
	c2	0.0573	0.0315	−0.004,0.12	26.8
5	CaOut = exp(a0+b1×rac0+c1×dur) × (1+c2×cumOTr) × expt				-2ln(L) = 1073.709
	a0	−0.7895	0.6894	−2.14,0.56
	b1	0.4967	0.7242	−0.92,1.92
	c1	−0.0402	0.0152	−0.070,-0.011	5.8
	c2	0.3184	0.2942	−0.26,0.90	22.6
6	CaOut = exp(2a0+b1×rac0) × (exp(c1×dur)+c2×cumOTr) × expt				-2ln(L) = 1079.407
	a0	−0.2868	0.4536	−1.18,0.60
	b1	0.5794	0.7238	−0.84,2.00
	c1	−0.0101	0.0545	−0.12,0.097	0.07
	c2	0.0575	0.0306	−0.003,0.12	17.2

Note: CaOut – predicted incident cases of bladder cancer, expt – expected cases from reference population,

rac0 – indicator of non-white race (0,1), dur – employment duration, cumOTr – cumulative exposure rank, in unit-years.

^aReference rates for six states (Pennsylvania, California, Ohio, Texas, Florida, and New York excluding New York City).

^bc2 is the estimate for the exposure response, or, excess relative rate per rank-year of exposure.

^cWald CI not appropriate for linear relative rate term: c2.

Abbreviations: CI, confidence interval; SIR, standardized incidence ratio.