Monitoring Colorectal Cancer Screening at Scale: Conformance Checking and Bottleneck Detection in Northern Portugal

Area of Science:

• Public Health
• Gastroenterology
• Health Services Research

Background:

• Population-based colorectal cancer (CRC) screening programs aim to detect cancer early.
• Positive faecal immunochemical test (FIT) results necessitate timely follow-up for diagnosis.
• Effective primary care coordination is crucial for managing screening pathways.

Purpose of the Study:

• To evaluate follow-up adherence after positive FIT results in a national CRC screening program.
• To identify pathway drift and operational bottlenecks affecting primary care coordination.
• To assess the impact of process variations on diagnostic colonoscopy timeliness.

Main Methods:

• Retrospective service evaluation using administrative event-log data (2018-2025) from Portugal.
• Analysis of 6.96 million events from 1.18 million invited individuals.
• Comparative analysis of screening episodes (2022-2023 vs. 2024-2025) focusing on pathway variants, conformance precision, alignment cost, and dwell times.

Main Results:

• Approximately 60% of FIT-positive episodes proceeded to colonoscopy within 365 days.
• Significant operational drift observed, with increased dwell times for FIT mailing-to-return and laboratory result-to-follow-up transitions.
• Conformance precision decreased from 0.65 to 0.45 when comparing recent to baseline models, indicating behavioral drift.

Conclusions:

• Routine pathway monitoring is essential for detecting incomplete follow-up and operational drift missed by participation metrics.
• Findings support targeted interventions in primary care, including reminder systems and referral tracking.
• Ensuring protected capacity for timely diagnostic colonoscopies is critical for program effectiveness.