Because cervical cancer is slow growing, considerable uncertainty surrounds the issue of the optimal screening interval. The most direct evidence about this issue comes from a prospective cohort analysis of a randomized controlled trial.[1] Among 2,561 women (mean age 66.7 years) with normal Papanicolaou (Pap) tests at baseline, 110 had an abnormal Pap test within the next 2 years. No woman was found to have cervical intraepithelial neoplasia (CIN) 2–3 or invasive cancer, and only one had CIN 1–2. Thus the positive-predictive value (PPV) of screening 1 year after a negative Pap test was 0%; after 2 years the PPV was 0.9%. The authors concluded that Pap tests should not be repeated within 2 years of a prior negative test.

A large study that included data from the National Breast and Cervical Cancer Early Detection Program together with modeling found little further mortality reduction from cervical cancer for screening every year as compared with screening every 3 years.[2]

References

1. Sawaya GF, Grady D, Kerlikowske K, et al.: The positive predictive value of cervical smears in previously screened postmenopausal women: the Heart and Estrogen/progestin Replacement Study (HERS). Ann Intern Med 133 (12): 942-50, 2000.  [PUBMED Abstract]
   
   
2. Sawaya GF, McConnell KJ, Kulasingam SL, et al.: Risk of cervical cancer associated with extending the interval between cervical-cancer screenings. N Engl J Med 349 (16): 1501-9, 2003.  [PUBMED Abstract]
   
   

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