Cervical-cancer screening: attendance and cost-effectiveness.

The influence of attendance on the health effects and cost-effectiveness of cervical-cancer screening was studied, both for organized screening programmes and for spontaneous screening. The asymmetric distribution of smears among the female population and the higher risk incurred by women who never or only occasionally attend screening appear crucial in determining the health effects of screening. An increase in attendance rate induces a substantial rise in health effects and a less than proportionate rise in costs, thus improving cost-effectiveness. Wider screening coverage, in order to increase the number of life-years saved, is achieved more efficiently by encouraging a greater number of women to attend than by inviting the same number of women to attend more often, i.e., with a shorter interval between successive screens. Spontaneous screening is characterized by high coverage for younger women and low coverage for middle-aged and older women. This leads to a small amount of health effects and poor cost-effectiveness as compared with organized screening.