This systematic review aimed to synthesise evidence on diagnostic colonoscopy completion and time to colonoscopy following abnormal stool-based colorectal cancer (CRC) screening tests. The review also examined the implementation strategies and health-system configurations used to support timely follow-up after abnormal faecal immunochemical test (FIT), guaiac faecal occult blood test (gFOBT) or multitarget stool DNA-FIT results.
The review was conducted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and used the Synthesis Without Meta-analysis reporting guideline. Searches were performed in MEDLINE via PubMed, Embase via Ovid and Scopus for articles published between 1 January 2010 and 28 October 2025. Reference lists of included studies were also screened.
Eligible study designs included randomised and non-randomised trials, observational studies, mixed-methods studies and programme evaluations. Included participants were adults with abnormal stool-based CRC screening tests (FIT, gFOBT or multitarget stool DNA-FIT). Studies had to report diagnostic colonoscopy completion, time to colonoscopy or implementation-related outcomes.
Studies were screened against the eligibility criteria noted above. The final synthesis included 25 studies, most originating from high-income settings. Because of heterogeneity in settings, study designs and outcome definitions, the authors did not pool results quantitatively and instead performed a narrative synthesis.
A piloted form was used to extract study characteristics, implementation strategies, colonoscopy completion, time-to-colonoscopy and sociodemographic differences. Risk of bias was assessed using design-appropriate tools: the Revised Cochrane risk-of-bias tool for randomised trials, the Risk of Bias in Non-randomised Studies of Interventions (ROBINS-I) or Joanna Briggs Institute tools, depending on study design. Certainty of evidence was evaluated using GRADE.
Reported follow-up intervals were grouped approximately into three windows for synthesis: about ≤3 months, about ≤6 months and about ≤12 months. Outcomes of interest were the proportion completing diagnostic colonoscopy within these intervals and measures of time elapsed from abnormal stool test to colonoscopy.
Twenty-five studies met inclusion criteria. The body of evidence was predominantly observational and largely derived from high-income health systems. Study settings included federally qualified health centres and safety-net settings, as well as organised and integrated screening programmes. Details on individual study populations, sample sizes and precise intervention components were extracted but are not reproduced here beyond the summary findings reported below.
Across studies, reported completion within 6–12 months varied substantially by setting. In federally qualified health centres and safety-net settings, completion within the 6–12 month window commonly ranged from approximately 30% to 55%. By contrast, organised and integrated programmes more commonly reported completion rates of 70%–80% or higher within similar time frames. The review found lower and more variable completion for earlier intervals (approximately ≤3 months), but certainty was very low for those estimates.
Reported time to diagnostic colonoscopy after an abnormal stool test ranged roughly from 42 to 184 days across included studies. Shorter delays were more frequently reported in higher-performing programmes that incorporated specific implementation elements (see next section). Certainty of evidence for time-to-colonoscopy estimates was graded very low.
Studies that reported higher colonoscopy completion and shorter times to colonoscopy commonly described combinations of the following implementation strategies and system configurations:
Registry-based tracking or real-time tracking of abnormal results, enabling identification of patients needing follow-up.
Clearly assigned responsibility or ownership for abnormal results, so that accountability for arranging follow-up was established.
Proactive outreach or patient navigation to contact patients, address barriers and facilitate scheduling.
Coordinated colonoscopy scheduling, including streamlined processes to secure timely procedure appointments.
Programmes that combined these elements—tracking, ownership, outreach/navigation and integrated scheduling—were more likely to report higher follow-up proportions and shorter delays. The review emphasises that the evidence does not establish causal effects for specific bundles because most studies were observational and heterogeneous in design and reporting.
Of the 25 included studies, one was judged to have low overall risk of bias, 19 were judged moderate risk and five were judged serious risk. The GRADE assessment indicated low certainty of evidence for colonoscopy completion at approximately 6 and 12 months, and very low certainty for approximately 3-month completion and for time-to-colonoscopy outcomes. Heterogeneity in study designs, settings and outcome definitions limited confidence in pooled or comparative conclusions.
Higher-performing post-abnormal-test pathways commonly incorporated registry-based tracking, explicit ownership of abnormal results, proactive outreach or navigation and coordinated access to colonoscopy. However, because the evidence is heterogeneous and largely observational, confidence in the comparative performance of specific implementation bundles is limited.
Health systems that serve under-resourced populations—such as federally qualified health centres and safety-net settings—may require targeted investments in tracking systems, navigation services and integrated scheduling to improve timely and equitable follow-up after abnormal stool-based screening. The review’s authors registered the protocol with PROSPERO (CRD42024579672).