Background: Colorectal cancer screening effect on right-sided colorectal neoplasia is limited. We compared fecal immunochemical test and simulated sigmoidoscopy diagnostic accuracy for advanced right-sided neoplasia detection.
Methods: We analyzed 1,292 individuals with complete screening colonoscopy with a fecal immunochemical test determination before colonoscopy. Sigmoidoscopy and "hybrid strategy" (sigmoidoscopy or fecal hemoglobin concentration ≥ 20 µg hemoglobin/g) diagnostic yield were simulated according to UK Flexible Sigmoidoscopy, Screening for COlon REctum (SCORE), and Norwegian Colorectal Cancer Prevention (NORCCAP) trials criteria to complete colonic examination. We compared sensitivity and specificity of both strategies and of "hybrid strategy" for advanced right-sided neoplasia with McNemar test.
Results: An advanced right-sided neoplasia was detected in 47 (3.6 %) subjects. A fecal hemoglobin concentration ≥ 20 µg hemoglobin/g was determined in 6.6 % of the subjects and 10.1, 12.7, and 23.5 % met UK, SCORE, and NORCCAP criteria, respectively. Fecal immunochemical test was statistically more specific than sigmoidoscopy strategies (93.8 %, UK 90.3 %, SCORE 87.7 %, NORCCAP 77.8 %; p < 0.001). In contrast, fecal immunochemical test sensitivity for advanced right-sided neoplasia (17 %) was not statistically different than UK (21.3 %; p = 0.7) or SCORE (23.4 %; p = 0.5), although it was inferior than NORCCAP strategy (42.5 %; p < 0.001). Adding fecal immunochemical test to sigmoidoscopy increased number of positives (8.5-25.7 %), sensitivity (10-30 %), and significantly reduced advanced right-sided neoplasia specificity (p < 0.001).
Conclusions: Fecal immunochemical test and sigmoidoscopy diagnostic yield for advanced right-sided neoplasia are low. Fecal immunochemical test is more specific than sigmoidoscopy but less sensitive than sigmoidoscopy according to NORCCAP criteria.