Outcome | Area | IRR Int versus Cont | 95% CI for IRR | p Value | |||

Control (n=9 practices) | Intervention (n=11 practices) | ||||||

Time | |||||||

Before | Number of lung cancer diagnoses | 47 | 59 | ||||

Population at risk | 43 444 | 67 119 | |||||

Rate/100 000 population/year | 108 | 88 | 0.81 | 0.55 | 1.19 | 0.288 | |

After | Number of lung cancer diagnoses | 42 | 75 | ||||

Population at risk | 43 444 | 67 119 | |||||

Rate/100 000 population/year | 97 | 112 | 1.16 | 0.79 | 1.69 | 0.452 | |

Interaction^{*} | 1.42 | 0.83 | 2.44 | 0.199 | |||

Time | |||||||

Before | Number of x-rays | 1605 | 2875 | ||||

Population at risk | 43 444 | 67 119 | |||||

Rate/100 000 population/year | 3690 | 4280 | 1.16 | 1.09 | 1.23 | 0.001 | |

After | Number of x-rays | 1573 | 3442 | ||||

Population at risk | 43 444 | 67 119 | |||||

Rate/100 000 population/year | 3620 | 5130 | 1.42 | 1.33 | 1.50 | 0.001 | |

Interaction^{*} | 1.22 | 1.12 | 1.33 | 0.001 |

↵* The interaction term represents the change over time in the outcome (ie, after minus before) for the intervention area minus the same effect for the control area.

Cont, control; Int, intervention; IRR, incidence rate ratio.