Detection rates for abnormal cervical smears: what are we screening for?

Area of Science:

• Gynecologic Oncology
• Preventive Medicine
• Public Health

Background:

• Cervical cancer screening programs aim to reduce mortality.
• The Bristol screening program began in 1966.
• High population uptake and good organization have characterized the program.

Purpose of the Study:

• To analyze the rates of detection for smear abnormalities in the Bristol screening program.
• To evaluate the effectiveness of cervical cancer screening in reducing death rates.
• To assess the overall impact and potential harms of the screening program.

Main Methods:

• Analysis of detection rates for smear abnormalities.
• Review of screening data from 1988 to 1993, covering 225,974 women.
• Comparison of detected abnormalities with the incidence of cervical cancer.

Main Results:

• High rates of smear abnormalities detected (15,551 women).
• A significant number of women (nearly 6000) were referred for colposcopy.
• The impact of screening on cervical cancer death rates in Bristol was statistically insignificant.
• The number of detected abnormalities was disproportionately high compared to the actual incidence of cervical cancer.

Conclusions:

• The Bristol cervical screening program, despite good organization and high uptake, resulted in excessive detection of abnormalities and referrals.
• The study suggests that much effort was spent managing harms to healthy women and avoiding litigation, rather than solely preventing cancer.
• The findings underscore the critical need for thorough prior evaluation of both benefits and harms in controlled trials before implementing any new screening test.