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
ModelDependent variableExplanatory variable (units)IRR (95%CI)Significance (p value)
Full modelTBTOTPCROWD (%)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 modelTBNZ<40PCROWDNZ<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.