Follow-up colonoscopy after abnormal stool-based colorectal cancer screening: a systematic review of completion, timeliness and implementation strategies

Objectives To synthesise evidence on diagnostic colonoscopy completion and time-to-colonoscopy after abnormal stool-based colorectal cancer screening tests and to examine the implementation strategies and health-system configurations used to support follow-up. Design Systematic review with narrative synthesis, reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement and the Synthesis Without Meta-analysis reporting guideline. Data sources We searched MEDLINE via PubMed, Embase via Ovid and Scopus for articles published from 1 January 2010 to 28 October 2025. Reference lists of included studies were also screened. Eligibility criteria Randomised and non-randomised trials, observational studies, mixed-methods studies and eligible programme evaluations involving adults with an abnormal faecal immunochemical test, guaiac faecal occult blood test or multitarget stool DNA-faecal immunochemical test were included. Eligible studies reported diagnostic colonoscopy completion, time to colonoscopy or implementation-related outcomes. Data extraction and synthesis Study characteristics, implementation strategies, colonoscopy completion, time-to-colonoscopy and sociodemographic differences were extracted using a piloted form. Risk of bias was assessed using the Revised Cochrane risk-of-bias tool for randomised trials, the Risk of Bias in Non-randomised Studies of Interventions or the Joanna Briggs Institute tools, according to study design. Certainty of evidence was assessed using Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Because of differences in settings, study designs and outcome definitions, findings were synthesised narratively. Reported follow-up intervals were grouped into approximately ≤3, ≤6 and ≤12 months. Results Twenty-five studies were included, predominantly from high-income settings. Colonoscopy completion within 6–12 months commonly ranged from approximately 30% to 55% in federally qualified health centres and safety-net settings to 70%–80% or higher in organised and integrated programmes. Time to colonoscopy ranged from approximately 42 to 184 days. Higher completion and shorter delays were more commonly reported in programmes combining real-time tracking, clearly assigned responsibility, proactive outreach or navigation and coordinated colonoscopy scheduling. Of the 25 studies, 1 was judged to have low overall risk of bias, 19 moderate risk and 5 serious risk. Certainty of evidence was low for colonoscopy completion at approximately 6 and 12 months and very low for approximately 3-month completion and time to colonoscopy. Conclusions Higher-performing post-abnormal-test pathways commonly incorporated registry-based tracking, clear ownership of abnormal results, proactive outreach or navigation and coordinated access to colonoscopy. However, confidence in the comparative performance of specific implementation bundles is limited by heterogeneous and predominantly observational evidence. Health systems serving under-resourced populations may require targeted investment in tracking, navigation and integrated scheduling to improve timely and equitable follow-up. PROSPERO registration number PROSPERO CRD42024579672.