Accuracy of Fecal Immunochemical Tests for Detecting Advanced Colorectal Neoplasia at Surveillance Colonoscopy

US guidelines recommend surveillance colonoscopy after polyp removal, but stool testing may offer a more efficient, acceptable strategy for patients with nonadvanced lesions. We conducted exploratory analyses to evaluate the diagnostic accuracy of quantitative fecal immunochemical testing (FIT) results to diagnose advanced colorectal neoplasia in patients undergoing surveillance colonoscopy.

We classified patients by previous colonoscopy findings as having low, intermediate, or high risk polyps. We compared the diagnostic performance for detecting advanced colorectal neoplasia at an optimal cutoff identified by the Youden index vs the standard cutoff of 100 ng/mL. We also estimated cumulative sensitivity and specificity for serial FIT testing in patients with nonadvanced findings.

Among the 449 participants (mean ± SD age 65.4 ± 7.1, 53.2% women, and 92.7% White), the median interval between colonoscopies was 5.0 years (IQR 3.5, 5.6); adequate or better bowel prep was achieved in 89.3%, and cecal intubation in 98.4%. We detected 55 advanced precancerous lesions, but no cancers. For patients with previous nonadvanced lesions (n = 378), the optimal cutoff was 26 ng/mL. Compared with the standard cutoff, the optimal cutoff increased sensitivity (14.3%-35.7%, P < 0.01) but reduced specificity (95.5%-79.2%, P < 0.01). Estimated cumulative sensitivity across 3 rounds of FIT testing was 73.4% at the optimal cutoff vs 37.1% with the standard cutoff.

Lowering the FIT hemoglobin cutoff markedly improved sensitivity for detecting advanced precancerous lesions in patients without previous advanced polyps. Serial testing could further enhance detection. FIT-based surveillance should be further evaluated as a potential strategy to prioritize, delay, or replace colonoscopy.