Faecal Occult Blood Tests Show Lower Colorectal Cancer Detection Rates in the Proximal Colon in Colonoscopy-verified Diagnostic Studies

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 Systematic Review With Meta-analysis - Faecal Occult Blood Tests Show Lower Colorectal Cancer Detection Rates in the Proximal Colon in Colonoscopy-verified Diagnostic Studies

Aliment Pharmacol Ther. 2016;43(7):755-764

 This study has some limitations. First, the detection rates of CRC in the proximal or distal colon may be different across different age, gender, race and number of samples. A previous study showed that age had a greater effect on proximal CRC;^[44] it may affect the diagnostic performance in different anatomic location. Secondly, there exist numerous brands of FOBTs.^[45] Diagnostic performance may be verified from brands to brands; however, subgroup analysis of FOBT brands could not be performed due to lack of studies. Third, this study included both symptomatic and asymptomatic patients; pooled results may not reflect FOBT performance under screening setting. Inclusion of symptomatic patients might overestimate the sensitivity. Also, for studies recruiting cancer patients, stool collection might take place after colonoscopy; endoscopic biopsy of polyps or cancers may cause bleeding and induce overestimation of sensitivity. Fourth, as FOBT aim at CRC detection, this study evaluated diagnostic performance of FOBTs for CRC detection only; detection of advanced adenoma was not performed in this meta-analysis. The stage of cancer affects the performance of FOBT; however, it was not well-documented in primary studies. Subgroup analysis of stage of cancer was not available; results in this meta-analysis do not reflect early stage disease. Finally, some unpublished studies may not have been identified through the literature search in OVID databases and publication bias may exist in this meta-analysis. Lastly, studies showed substantial heterogeneity.

 In conclusion, this systematic review and meta-analysis showed that FOBT, both gFOBT and iFOBT, have a better diagnostic performance for the relative detection of CRC in the distal colon than that in the proximal colon.