Header: Chat GPT rapidly answers general medical questions, here, slippage in colon cancer screening.
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We had a screening colonoscopy in the family recently and I wondered:
1) Of stool tests ordered, what percent get completed (e.g. mailed back)?
2) Of positive stool tests, what percent get the indicated colonoscopy?
Below is the direct output from Chat GPT. I'm not taking it as gospel truth, nor have I fact-checked it. However, it's probably directonally correct (or better) and there aren't perfect or absolute answers, anyway.
It's pretty good for, "almost free" and "takes a few seconds."
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Completion of Stool-Based Colorectal Cancer Screening
How often is an ordered stool test completed?
FIT, United States. FIT completion varies substantially because an “order” may involve anything from handing a kit to the patient to mailing it with reminders and navigation. A reasonable practical estimate is that approximately 35%–50% of ordered or mailed FIT kits are returned in ordinary US outreach programs. In a pragmatic federally qualified health-center program, approximately 46% of ordered FITs were completed in the first year and 41% in the second. Prior behavior strongly predicted adherence: previous completers were much more likely to complete subsequent testing than previous noncompleters (Nielson et al., 2019). Programs with minimal follow-up may achieve only about 20%–35%, whereas organized mailing, reminders, and navigation can raise completion above 50%.
Cologuard/mt-sDNA, United States. Completion of an ordered Cologuard test is generally reported at about 70% within one year. Among 368,494 Medicare beneficiaries with a valid order, 44% completed the test within 30 days, 65% within 60 days, and 71% within one year (Weiser et al., 2021). A later national analysis of approximately 1.56 million first-time users similarly reported 71.3% overall completion, although completion among Medicaid beneficiaries was only 52.0% (Le et al., 2025). These findings are consistent with the likelihood that Exact Sciences’ centralized fulfillment, patient reminders, customer assistance, and tracking infrastructure improve completion relative to low-cost FIT programs. However, these are observational studies, often using Exact Sciences laboratory data, and they do not isolate the independent effect of the company’s outreach system.
Outside the United States. Organized national and regional FIT programs usually measure participation among everyone invited rather than among patients receiving a physician order. Across European programs, average FIT participation was approximately 49.5%, with a wide range of roughly 23%–71% (Senore et al., 2019). Thus, even an organized population program typically reaches only about half of eligible invitees, although the strongest programs approach 70%.
| Test and setting | Approximate completion |
|---|---|
| US FIT, ordinary ordered or mailed programs | 35%–50% |
| US FIT, low-touch or disadvantaged settings | 20%–35% |
| US FIT, intensive organized outreach | 50%–60% or higher |
| US Cologuard, insured populations | About 70% |
| US Cologuard, Medicaid | About 50% |
| European organized FIT invitation | About 50% average; approximately 23%–71% range |
Colonoscopy After a Positive Stool Test
United States, stool tests combined. In a large study involving nearly 33,000 patients with a positive FIT, guaiac FOBT, or mt-sDNA result across 39 US healthcare organizations, 51.4% underwent colonoscopy within six months and 56.1% within one year (Mohl et al., 2023). The relatively small increase between six and twelve months suggests that the problem is not merely delayed scheduling; many patients with positive stool tests never complete the recommended diagnostic colonoscopy.
Positive Cologuard versus positive FIT. Some US studies have reported substantially higher colonoscopy follow-up after positive mt-sDNA than after positive FIT or FOBT. In one integrated-system analysis, six-month colonoscopy completion was 84.9% after positive mt-sDNA versus 42.6% after positive FIT/FOBT (Finney Rutten et al., 2020). This comparison should be interpreted cautiously because the positive mt-sDNA and FIT groups were small and unequal, and selection, insurance, clinician behavior, and manufacturer-supported communication may have contributed to the difference. Nonetheless, the findings are consistent with the hypothesis that a centralized, trackable Cologuard system produces more persistent follow-up than decentralized FIT testing.
Outside the United States. Organized FIT programs generally achieve better follow-up. An international survey of 35 screening programs found a mean 79% colonoscopy completion rate within six months, although performance varied considerably among programs (Selby et al., 2021). European screening programs have reported average compliance with colonoscopy referral of approximately 81%, with program-level rates ranging from about 64% to 92% (Senore et al., 2019).
A large Italian organized-program study included 111,423 people with positive FIT results; approximately 79% completed colonoscopy. Patients who did not undergo colonoscopy subsequently had about twice the risk of colorectal-cancer death as those who completed the diagnostic examination, although the comparison was observational and residual differences between compliers and noncompliers may remain (Zorzi et al., 2022).
| Setting after positive stool test | Colonoscopy completion |
|---|---|
| United States, stool tests combined | 51% by 6 months; 56% by 12 months |
| United States, positive FIT in routine settings | Approximately 40%–55% |
| United States, positive Cologuard in selected studies | Approximately 70%–85% |
| Organized international FIT programs | Approximately 79%–81% |
| Highest-performing European programs | Approximately 90% or higher |
Overall Interpretation
The literature identifies two major points of attrition. First, only about four in ten to one-half of US patients complete an ordinary FIT order, whereas approximately seven in ten complete an ordered Cologuard test. The difference likely reflects not only the test itself but also Exact Sciences’ centralized logistics, reminders, patient support, and ability to track an unreturned kit.
Second, after a positive stool test, only about half of US patients receive colonoscopy within six to twelve months, compared with roughly four-fifths in organized non-US programs. Positive Cologuard results appear to receive better follow-up than positive FIT results in some studies, but the magnitude of that advantage remains uncertain because the available comparisons are observational and frequently involve manufacturer-generated data.
References
Nielson CM, Vollmer WM, Petrik AF, et al. Factors affecting adherence in a pragmatic trial of annual fecal immunochemical testing for colorectal cancer. Journal of General Internal Medicine. 2019;34:978–985. doi:10.1007/s11606-018-4820-0.
Weiser E, Parks PD, Swartz RK, et al. Cross-sectional adherence with the multi-target stool DNA test for colorectal cancer screening: real-world data from a large cohort of older adults. Journal of Medical Screening. 2021;28:18–24. doi:10.1177/0969141320903756.
Le QA, Greene M, Gohil S, et al. Adherence to multi-target stool DNA testing for colorectal cancer screening in the United States. International Journal of Colorectal Disease. 2025;40:16. doi:10.1007/s00384-025-04805-0.
Mohl JT, Ciemins EL, Miller-Wilson LA, et al. Rates of follow-up colonoscopy after a positive stool-based screening test result for colorectal cancer among health care organizations in the US, 2017–2020. JAMA Network Open. 2023;6:e2251384. doi:10.1001/jamanetworkopen.2022.51384.
Finney Rutten LJ, Jacobson DJ, Jenkins GD, et al. Colorectal cancer screening completion: an examination of differences by screening modality. Preventive Medicine Reports. 2020;20:101202. doi:10.1016/j.pmedr.2020.101202.
Selby K, Senore C, Wong MCS, et al. Interventions to ensure follow-up of positive fecal immunochemical tests: an international survey of screening programs. Journal of Medical Screening. 2021;28:51–53. doi:10.1177/0969141320904977.
Senore C, Basu P, Anttila A, et al. Performance of colorectal cancer screening in the European Union member states: data from the second European screening report. Gut. 2019;68:1232–1244. doi:10.1136/gutjnl-2018-317293.
Zorzi M, Battagello J, Selby K, et al. Non-compliance with colonoscopy after a positive faecal immunochemical test doubles the risk of dying from colorectal cancer. Gut. 2022;71:561–567. doi:10.1136/gutjnl-2020-322192.
