Background: Faecal immunochemical tests (FITs) are recommended for colorectal cancer screening. Two frequently used FIT methods (FOB-Gold, Sentinel Diagnostics, Milan, Italy and OC-Sensor, Eiken Chemical, Tokyo, Japan) perform similarly in detecting advanced neoplasia (ie, colorectal cancer and advanced adenoma) at a fixed positivity cutoff for faecal haemoglobin concentration. It is unclear whether the performance of the two methods is also comparable at other thresholds. We compared the accuracy of the two assays in detecting advanced neoplasia across various thresholds.
Methods: In a cross-sectional study in the Dutch national screening programme, individuals who were screening naive in 2016 (aged 55-75 years) living in the southwest region of the Netherlands were invited to use two different FIT assays on the same bowel movement. Eligible participants were randomly selected from municipal registers. Participants were referred for colonoscopy if either FIT assay result met the predefined positivity threshold (≥15 μg haemoglobin per g faeces). We compared the respective distributions of reported haemoglobin concentration and positivity rates with various FIT positivity thresholds. The performance of each FIT for identifying advanced neoplasia at colonoscopy in FIT-positive assays was compared with the area under the receiver operating characteristic curve.
Findings: 21 078 (50·0%) of 42 179 invitees completed both FIT assays. The distribution of haemoglobin concentrations differed significantly between the two FITs (p<0·0001), with higher positivity rates for OC-Sensor at FIT thresholds of 5 and 10 μg haemoglobin per g faeces, similar positivity rates at 15 and 20 μg haemoglobin per g faeces, and higher rates for FOB-Gold at FIT thresholds of 25-150 μg haemoglobin per g faeces. 2046 (9·7%) of 21 078 participants had at least one FIT assay that was positive and of these, 1724 (84·3%) attended colonoscopy. The accuracy of results in individuals undergoing colonoscopy did not significantly differ between the FITs, with an area under the receiver operating characteristic curve of 0·675 (95% CI 0·649 to 0·702) for FOB-Gold and 0·686 (0·661 to 0·712) for OC-Sensor (p=0·40). At identical positivity rates, the positive predictive value of the two FIT assays was similar (difference varying from 0·5% [95% CI -2·6 to 3·7] at a positivity rate of 3·5% to 2·4% [-2·5 to 7·3] at a positivity rate of 2·0%).
Interpretation: The two widely used FITs have significantly different distributions of reported haemoglobin concentration and yield different positivity rates at equal thresholds. However, they perform similarly in detecting advanced neoplasia at a preset positivity rate. When implementing either FIT in a screening programme, the desired positivity rate that identifies participants to be referred for colonoscopy should first be set, guided by available resources and feasibility.
Funding: The Netherlands Organisation for Health Research and Development.
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