Prediction of the severity of colorectal lesion by fecal hemoglobin concentration observed during previous test in the French screening program.

BACKGROUND: The rate of positive tests using fecal immunochemical test (FIT) does not decrease with subsequent campaigns, but the positive predictive value of advanced neoplasia significantly decreases in subsequent campaign after a first negative test. A relationship between the fecal hemoglobin concentration (Fhb) and the opportunity to detect a colorectal cancer in subsequent campaign has been shown. AIM: To predict the severity of colorectal lesions based on Fhb measured during previous colorectal cancer screening campaign. METHODS: This etiological study included 293750 patients aged 50-74, living in Auvergne-Rhône-Alpes (France). These patients completed at least two FIT [test(-1) and test(0)] between June 2015 and December 2019. Delay between test(-1) and test(0) was > 1 year and test(-1) result was negative (< 150 ngHb/mL). The severity of colorectal lesions diagnosed at test(0) was described according to Fhb measured at test(-1) [Fhb(-1)]. The relationship between the severity classified in seven ordinal categories and the predictive factors was analyzed in an ordered multivariate polytomous regression model. RESULTS: The test(0) positive rate was 4.0%, and the colonoscopy completion rate was 97.1% in 11594 patients who showed a positive test(0). The colonoscopy detection rate was 77.7% in those 11254 patients who underwent a colonoscopy. A total of 8748 colorectal lesions were detected (including 2182 low-risk-polyps, 2400 high-risk-polyp, and 502 colorectal cancer). The colonoscopy detection rate varied significantly with Fhb(-1) [0 ngHb/mL: 75.6%, (0-50 ngHb/mL): 77.3%, (50-100 ngHb/mL): 88.7%, (100-150 ngHb/mL): 90.3%; P = 0.001]. People with a Fhb(-1) within (100-150 ngHb/mL) (P = 0.001) were 2.6 (2.2; 3.0) times more likely to have a high severity level compared to those having a Fhb(-1) value of zero. This risk was reduced by 20% in patients aged 55-59 compared to those aged < 55 [adjusted odds ratio: 0.8 (0.6; 1.0)]. CONCLUSION: The study showed that higher Fhb(-1) is correlated to an increased risk of severity of colorectal lesions. This risk of severity increased among first-time participants (age < 55) and the elderly (≥ 70). To avoid the loss of chance in these age groups, the FIT positivity threshold should be reduced to 100 ngHb/mL. The other alternative would be to reduce the time between the two tests in these age groups from the current 2 years to 1 year.