Diagnostic efficacy of fecal calprotectin combined with a high-sensitivity quantitative fecal immunochemical test for colorectal tumors

BACKGROUND Fecal calprotectin (FC) has demonstrated good efficacy in assessing disease activity in inflammatory bowel disease; however, its value in detecting colorectal cancer (CRC) remains unclear. Although most symptomatic patients actually present with normal or minor pathological findings, they often still undergo colonoscopy in many clinical scenarios, resulting in unnecessary utilization of healthcare resources. AIM To investigate the diagnostic value of FC in colorectal tumors, and to determine whether the combination of FC with high-sensitivity quantitative fecal immunochemical test (hs-qFIT) can improve diagnostic efficacy for colorectal tumors compared to either test alone. METHODS We enrolled medium- and high-risk individuals for CRC who underwent colonoscopy in the Department of Gastroenterology and Hepatology or received surgical treatment in the Department of General Surgery at the First Medical Center of Chinese People’s Liberation Army General Hospital between March 2024 and January 2026. FC and hs-qFIT were performed prior to colonoscopy or gastrointestinal surgery. The diagnostic performance of FC, hs-qFIT, and their combination for CRC and adenomas was evaluated by calculating sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC). RESULTS A total of 120 subjects were included in this study. The sensitivity of FC for diagnosing CRC was 77.5% [95% confidence interval (CI): 61.7%-88.6%], the specificity was 65% (95%CI: 48.5%-78.8%), the positive predictive value (PPV) was 68.9% (95%CI: 53.5%-81.2%), the negative predictive value was 74.3% (95%CI: 57.1%-86.8%), and the AUC was 0.797 (95%CI: 0.697-0.897). The combination of FC and hs-qFIT increased the sensitivity for diagnosing CRC to 87.5% (95%CI: 73%-95.8%), increased the negative predictive value to 82.8% (95%CI: 64.7%-93.2%), and achieved an AUC of 0.866 (0.784-0.949), indicating that the combined strategy improves diagnostic performance for CRC. However, the combined test missed 12.5% of CRC cases. This strategy may help determine the urgency of further evaluation, but double-negative results cannot yet completely rule out a diagnosis of CRC. The combination of FC and hs-qFIT increased the sensitivity for diagnosing any colorectal lesion to 76.3% (95%CI: 65.5%-84.7%) and the PPV to 79.2% (95%CI: 68.5%-87.2%). Although the performance was poorer than that for CRC, the combined test may provide some guidance for referral of patients with colorectal lesions. CONCLUSION FC serves as a reliable biomarker for diagnosing CRC, and its combination with hs-qFIT further enhances both the sensitivity and negative predictive value for CRC detection, thereby improving the overall diagnostic efficacy for colorectal tumors.