What happens when organization of cervical cancer screening is delayed or stopped?

OBJECTIVES: Many countries rely on opportunistic screening, and data on its effectiveness are asked for. We assessed the impact on cervical cancer incidence and mortality of opportunistic screening compared with organized screening.
SETTING: Women aged 30-64 in Denmark, 1973-2002; 16 counties with different screening strategies.
METHODS: Cumulative incidence and mortality rates for women aged 30-64 by county. Poisson regression of incidence and mortality rates by age, calendar period and county. Interaction between type of county and calendar period measured the difference between counties with screening organized early versus late in time.
RESULTS: A statistically significant interaction was found between type of county and calendar period (P=0.0151) for cervical cancer incidence, but not for cervical cancer mortality (P=0.9593). The interaction terms were not statistically significant when a comparison was made between a single county in which an organized programme was interrupted for an 11-year period and other counties. There was, however, a statistically significant increased incidence and mortality rates at the restart of the organized programme.
CONCLUSION: Organization of cervical cancer screening accelerated the decline in cervical cancer incidence, compared with the trend in areas relying on opportunistic screening. No impact could be measured of the screening organization on cervical cancer mortality. A decade long stop of an organized screening programme was associated with a temporary increase in cervical cancer incidence and mortality. Coverage remains a key quality indicator in the ongoing modernization of screening technology.