The frequency of cervical cancer screening. Comparison of a mathematical model with empirical data.

The results of a mathematical model used to analyze the frequency of the Pap smear are compared with a recently published independent empirical study of data from large screening programs in Europe and North America. The model's predictions of the reduced incidence of invasive cervical cancer achieved with different screening frequencies match the empirical results closely--the predictions were within 1% of the empirical results for screening frequencies ranging from 1 to 10 years. The data indicate that compared with annual screening, screening every 2, 3, 5, and 10 years retains 99%, 97%, 89%, and 69%, respectively, of the effectiveness measured as a reduction in frequency of invasive cancer. The mathematical model underestimated the effectiveness of screening every 3 years, compared with screening every year.