The use of colon capsule endoscopy (CCE) in clinical practice has been challenging, mainly due to a high re-investigation rate caused by both incomplete investigations, and a high sensitivity to polyps requiring therapeutic intervention. A strategy to lower the re-investigation rate following CCE, could be to target patients with a lower risk of pathology. Faecal haemoglobin (fHb) is a well-known predictor of colorectal adenomas, and the concentration of fHb may therefore present as a good triaging measure. Therefore, we aimed to investigate the re-investigation rate and risk classification in complete CCEs in a screening population stratified by fHb concentration.

Complete colon capsule endoscopy investigations were identified from the intervention arm of a large randomised controlled trial, CareForColon2015(1,2), and the proportions of investigations leading to re-investigation by colonoscopy were stratified by fHb concentration. All participants had a faecal immunochemical test value ≥100 ng hb/mL buffer. Further, odds of re-investigation was estimated by logistic regression models and odds of increased risk classification by ordinal regression models. The risk classification in the current study was defined in four levels; Level one: no findings. Level two: less than three polyps, all smaller than 10 mm in size. Level three: three to four polyps of any size, or at least one polyp 10-19 mm in size. Level four: More than four polyps, or at least one polyp larger than 19 mm in size, or cancer suspicion.

The re-investigation rate was 58.4 % in 1,410 complete CCEs out of 2,030 procedures. There were no significant differences (p=0.283) in re-investigation rates between fHb concentration subgroups with 58.0 %, 61.1 %, and 62.7 % in the groups of 100-249, 250-499, and >499 ng hb/mL buffer, respectively. Level one or two risk classification was identified in 21.3 % (n=300) and 20.3 % (n=286) of the complete CCE investigations, returning the participant to the colorectal cancer screening. Level three or four risk classification was identified in 30.5 % (n=430) and 27.9 % (n=394) of the complete CCE investigations, resulting in referrals for follow-up colonoscopy. The odds of increased risk classification (i.e. higher than level one) was 1.18 (CI 95% 0.93; 1.51, p=0.177) for concentrations between 250-499 ng hb/mL buffer, and 1.36 (CI 95% 1.08; 1.70, p=0.008) for concentrations above 499 ng hb/mL buffer, compared to 100-249 ng hb/mL buffer.

Table 1: Odds of re-investigation and increased risk classification based on faecal haemoglobin concentration estimated from univariate and multivariate logistic and ordinal logistic regression models, n=1,410, reference group: 100-249 ng hb/mL buffer

Conclusion: Faecal haemoglobin concentration did not prove to be a good stand-alone selection parameter for diagnostic modality in a faecal immunochemical test positive colorectal cancer screening population, although it was significantly associated with an increased risk classification.