Table 2 Results of the Negative Binomial Regression models testing the relationship between the explanatory variables and TB in the total population (full model) and NZ-born population <40 (sub-model), 2000–4
 Model Dependent variable Explanatory variable (units) IRR (95%CI) Significance (p value) Full model TBTOT PCROWD (%) 1.05 (1.02 to 1.08) 0.001 PMIG (%) 1.03 (1.02 to 1.05) 0.000 INCOME ($1,000) 0.96 (0.95 to 0.98) 0.000 P<40 (%) 0.90 (0.89 to 0.91) 0.000 TB5YR (number) 1.01 (0.98 to 1.05) 0.496* Sub model TBNZ<40 PCROWDNZ<40 (%) 1.08 (1.04 to 1.12) 0.000 PMIG (%) 1.02 (0.99 to 1.04) 0.102* INCOMENZ<40 ($1000) 0.95 (0.93 to 0.98) 0.000 P<40 (%) 0.89 (0.87 to 0.91) 0.000 TBMIG5YR (number) 0.99 (0.91 to 1.07) 0.853* TBNZ5YR (number) 1.10 (0.93 to 1.31) 0.268*
• See table 1 for description of the variables; IRR, Incidence rate ratio.

• Note that an IRR of 1.08 for PCROWDNZ<40 in the sub-model, for example, means that a 1% increase in crowding in a CAU would be associated with an 8% increase in expected TB count in that CAU, assuming other variables were held constant.

• *Not significant.