Longitudinal trends in cervical cytological lesions and the effect of risk factors. A 30-year overview.
BACKGROUND
Cytological preinvasive changes are important precursors in cervical cancer, therefore variations in their trends affect screening guidelines.


METHODS
Trends in cytological preinvasive changes following the 1st to 5th screening visits in the 20-34 and 35-69 year age groups were analyzed for the period 1979-2002: a) the incidence rate (absolute risk) of higher grade cytology and the relative risk of risk factors on this rate; b) the cumulative incidence of low-grade and higher grade smears after normal and abnormal screening results; c) the cumulative incidence of higher grade cytology at a fixed risk level after normal screening results; and d) the prevalence of higher grade smears at first screening visit in the 20-24/25-29 year age groups during 1971-2002.


RESULTS
An increased trend in the prevalence of higher-grade smears was observed at the first screening visit after 1980. The main risk variables for higher-grade smears in both age groups were low-grade changes and inflammation followed in the younger age group by calendar year. However, age correlated with a decreased risk ratio. After normal screening the cumulative incidence rate of low and higher-grade smears increased almost linearly with time. The screening interval before diagnosis of higher-grade smears increased with both age and number of normal visits, but leveled out after the age of 35-40.


CONCLUSIONS
Trends in higher-grade smears indicate that screening should preferably start before age 25 with a maximum interval of 3 years. The interval can be extended after age 35-40. Low-grade smears or inflammation need closer follow-up.
Sigurdsson
Kristjan
K
Cancer Detection Clinic, Icelandic Cancer Society, Reykjavik, Iceland. kristjan@krabb.is
Sigvaldason
Helgi
H
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007249:Inflammation; D008137:Longitudinal Studies; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D011230:Precancerous Conditions / Q000453:epidemiology* / Q000473:pathology*; D015995:Prevalence; D012307:Risk Factors; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D014626:Vaginal Smears