Managing an extension of screening intervals: Avoiding boom and bust in health care workloads.

Extending screening intervals in ongoing cancer screening programmes can lead to challenging year-on-year variations in the number of screening tests. We explored how such variation could be diminished with a managed transition to the extended interval. We defined three extension scenarios: immediate extension for the entire target population; stepped transition by birth cohort; and gradual transition by reducing the number of available screening appointments. These were compared to a situation in which the interval remains unchanged in a demographic model covering a 15-year period. The model was populated with observed parameters from England, a real-world setting recommending cervical screening with 3-year intervals at age 25-49 and 5-year intervals at age 50-64. Informed by typical changes currently considered by several European programmes including the programme in England, we explored the effect on screening test numbers of an extension of the 3-year interval to 5 years for women younger than 50. All three extension scenarios resulted in similar cumulative numbers of screening tests, which were about 30% lower compared to a situation in which the interval would remain unchanged. However, the year-on-year variation in the number of screening tests varied between the scenarios. This variation was around 4-fold for the immediate scenario. In the stepped scenario, the yearly numbers could differ by around 20%, whereas in the gradual scenario they were virtually constant. A managed interval extension, transitioning different groups of the target population at different times, can substantially reduce the yearly variation in screening workload without increasing the total number of screening tests in the long term.