Large performance variation does not affect outcome in the Finnish cervical cancer screening programme

Area of Science:

• Gynecologic Oncology
• Public Health
• Laboratory Medicine

Background:

• Cytology screening is crucial for cervical cancer prevention, reducing incidence and mortality.
• High-quality screening programs require rigorous organization and quality control.
• Audit studies are essential for maintaining and improving screening quality.

Purpose of the Study:

• To evaluate interlaboratory variations in performance indicators for cervical cytology screening.
• To assess the impact of these variations on screening effectiveness, specifically CIN3+ rates after a negative screen.

Main Methods:

• Analysis of 953,610 screening tests from seven laboratories (1990-1999).
• Linking screening data with cancer registers to identify CIN3+ cases.
• Re-evaluation of smears from CIN3+ cases with prior negative screens and controls to determine false negative rates.

Main Results:

• Significant interlaboratory variation observed in follow-up recommendations (up to 3.6-fold) and referrals (up to 4.0-fold).
• Detection rates for CIN1, CIN2, and CIN3+ varied up to 8.5-fold, 5.4-fold, and 3.3-fold, respectively.
• False negative rates showed up to 2.1-fold differences (29-62%), but CIN3+ rates after negative screens remained low and consistent across laboratories.

Conclusions:

• Substantial variations exist in laboratory performance indicators and test validity for cervical cytology.
• Despite performance heterogeneity, overall screening effectiveness for CIN3+ was not significantly impacted.
• Addressing performance variations is important due to potential impacts on cost, treatment, and patient psychological burden.