Risk factors associated with false-positive fecal immunochemical test results in colorectal cancer screening

Fecal immunochemical test (FIT)-based screening has been recommended as an option for population colorectal cancer (CRC) screening. However, the studies on factors associated with false-positive FIT results are still limited. To identify the clinical and endoscopic factors associated with false-positive results of FIT for advanced neoplasia (AN) and to evaluate whether false-positive FIT results would be indicative of other digestive tract diseases. We prospectively enrolled 929 participants aged 50 years or older at Qilu Hospital of Shandong University between April 2020 and April 2021. The two-sample FIT was used in this study and ≥ 10 μg/g in either of two stool samples was regarded as the positive FIT result. All these participants underwent subsequent gastroscopy and colonoscopy. False positive FIT results were defined as positive FITs without AN detected in colonoscopies. With a cut-off value of 10 µg/g, the positive rate of FIT was 16.0%. For detecting AN, the sensitivity and specificity were 64.6% and 87.6%, respectively. After adjusting confounding factors, male (OR = 1.61; 95% CI, 1.05–2.48; P = 0.030), colorectal inflammation (OR = 2.99; 95% CI, 1.38–6.04; P = 0.003), presence of three or more non-advanced adenomas (OR = 1.78; 95% CI, 1.11–2.82; P = 0.015) and gastric cancer (OR = 11.33; 95% CI, 2.40–59.52; P = 0.002) were associated with higher risk of false-positive FIT results. Although the FIT results may be false-positive for detecting AN, they may still suggest medical issues that warrant closer medical follow-up and intervention. Meanwhile, routine upper endoscopy investigation for false positive patients was not recommended. Upper endoscopy may be considered conditionally in FIT-positive/AN-negative patients with additional risk factors. Large-scale research is required to clarify this issue. (ClinicalTrials.gov ID: NCT04454099) Trial identification number: ClinicalTrials.gov ID: NCT04454099 (URL: https://clinicaltrials.gov/ct2/show/NCT04454099) registered on July 1, 2020.