Patients with cumulative fecal hemoglobin concentration ≥20 µg/g feces over 2 negative tests should be referred for total colonoscopy due to elevated risk for advanced neoplasia (AN), according to a study published in Gut. Patients with undetectable concentrations can safely extend the interval between screenings.

This prospective cohort study enrolled participants from 4 population-based programs in Italy to estimate the potential predictive value of fecal hemoglobin concentration among participants with fecal immunochemical test (FIT) results below the positivity threshold for subsequent risk for AN, including colorectal cancer (CRC) and advanced adenoma. All programs utilized the same analytical procedure (OC Sensor® every 2 years on a single sample), as well as the same positivity cutoff (20 µg Hb/g feces). Participants were aged 50 to 74 and had an initial FIT between January 1, 2004, and December 31, 2010, and 2 or 3 subsequent FIT assessments (follow-up interval between 18 and 60 months). Eligible participants who had 2 consecutive negative FITs were followed over the next 2 rounds of testing to estimate the likelihood of a positive result at the third or fourth round of FIT assessment. Data were analyzed using multivariable logistic regression models and the Kaplan-Meier method.

The cumulative probability of having a positive FIT over the subsequent 2 rounds ranged from 48.4% (95% CI, 44.0-53.0) among participants with a cumulative fecal hemoglobin concentration ≥20  µg/g feces (0.7% of participants screened) in the initial 2 tests, and 7.8% (95% CI, 7.5-8.2) for patients with undetectable fecal hemoglobin (50% of participants screened) in the initial 2 tests. The corresponding figures for cumulative detection rate were 25.5% (95% CI, 21.4-30.2) and 1.41% (95% CI, 1.3-1.6) for AN and 4.5% (95% CI, 2.8-7.1) and 0.17% (95% CI, 0.12-0.23) for CRC.

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Assuming AN screen-detected at the third or fourth round of testing could already be detected at the time of the second FIT, total colonoscopy referral of patients with cumulative fecal hemoglobin levels ≥20 µg Hb/g feces at the second FIT would result in an AN detection yield at total colonoscopy of 25.5% (95% CI, 21.4-30.2), slightly lower than the observed rate of 30.1% (95% CI, 29.1-31.1). The 9% increase in total colonoscopy workload using this approach would be more than balanced by the 12% reduction in workload achieved by extending screening time intervals for patients with undetectable fecal hemoglobin levels.


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Study investigators conclude that using cumulative fecal hemoglobin concentration as a predictive value in FIT “might result in a more appropriate and more efficient utilization of endoscopy resources, while reducing unnecessary assessments among [low risk] patients. Sequential randomized trials would be needed to confirm these hypotheses. Effective communication strategies should be developed as well to adequately convey the information about risk tailored screening intervals among subjects with negative FIT results.”

Reference

Senore C, Zappa M, Campari C, et al. Faecal haemoglobin concentration among subjects with negative FIT results is associated with the detection rate of neoplasia at subsequent rounds: a prospective study in the context of population based screening programmes in Italy [published online August 27, 2019]. Gut. doi: 10.1136/gutjnl-2018-318198