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

BACKGROUNDThe 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. AIMTo predict the severity of colorectal lesions based on Fhb measured during previous colorectal cancer screening campaign. METHODSThis 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. RESULTSThe 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)]. CONCLUSIONThe 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.