Observations on FIT-Fecal DNA Testing in Clinical Practice

Observations on FIT-Fecal DNA Testing in Clinical Practice

Douglas K. Rex, MD, FASGE reviewing Vakil N, et al. Gastrointest Endosc 2020 Jan 2.

The commercially available FIT (fecal immunochemical test)-fecal DNA test is expensive, has a significant false-positive rate, particularly in the elderly, and is dominated by both FIT and colonoscopy from a cost-effectiveness perspective. 

In the Aurora Health Care system in Wisconsin, providers can order the FIT-fecal DNA test through Epic. In a one-year period ending June 1, 2018, 6835 tests were completed, of which 18% were positive. Of 1242 positive patients, 73% underwent colonoscopy, and the prevalence of cancer was 0.89%. An additional 17% had advanced conventional adenomas, and 9% had sessile serrated lesions. Colonoscopy performance appeared excellent, and of the 6835 patients who underwent fecal testing, ultimately 8% were proven to have cancer or an adenoma (thus an “adenoma detection rate” of 8%). If any cancer or adenoma was considered a successful outcome, then 39% of tests were false positive, and if only a significant adenoma or cancer was detected, then 78% were false positive.

Considering only the direct costs of the test at $649 per test, the cost to detect at least one adenoma (excluding the cost of follow-up colonoscopies) was $8,124, the cost to detect one advanced adenoma was $20,632, and the cost to detect cancer was $403,265.

COMMENT
These results suggest lower positive predictive values for cancer and advanced adenomas than published in some recent small studies. Significant problems include the 27% of patients with a positive test who did not undergo colonoscopy, and the relatively high cost. The results suggest that, in clinical practice, the test is being carried by its aggressive marketing, ease of ordering, and the longer adherence rates to screening (relative to FIT) provided by the 3-year screening interval.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Douglas K. Rex, MD, FASGE

CITATION(S)

Vakil N, Ciezki K, Huq N, Singh M. Multitarget stool DNA testing for the prevention of colon cancer: outcomes in a large integrated healthcare system. Gastrointest Endosc 2020 Jan 2. (Epub ahead of print) (https://doi.org/10.1016/j.gie.2019.12.027)

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