A computer simulation model for the practical planning of cervical cancer screening programmes.

There is ample evidence of the efficacy of cytological screening in the prevention of cervical cancer but disagreement on the form which screening programmes should take. Simulation models have been used as a convenient and rapid method of exploring the outcome of different screening policies and of demonstrating the importance and interrelationships of the variables concerned. However, most such models are either too abstract or too simplistic to be of practical value in planning screening programmes. A model is described which reproduces demographic events in a female population (that of England and Wales) over a 30 year period, and onto this superimposes the natural history of cervical carcinoma, using data derived from published studies. A microsimulation approach--each individual in the population being retained as a unit--allows factors such as disease onset and screening uptake to be dependent upon personal characteristics and past events. Screening can be offered as part of a routine programme, or incidentally--for example during pregnancy or hospital attendance. The model allows quantitative evaluation of the complex patterns of screening that are actually observed and the relative importance of the different components of such screening programmes. Assumptions about natural history can thus be studied.