Evaluation of the diagnostic performance of immunochemical fecal occult blood tests in patients with high carcinogenic risk

Colorectal cancer (CRC) remains one of the leading causes of cancer morbidity and mortality in Russia. Early diagnosis enables the detection of pathology at preclinical stages, improving prognosis and reducing healthcare costs. The main tool is population-based screening programs, regulated by the Order of the Ministry of Health of the Russian Federation No. 404n (2021), which include fecal occult blood testing. However, discussions persist regarding the clinical significance of the method and the optimal management of high-risk patients. In practice, both qualitative and quantitative tests are used. The former are suitable for individual use, while the latter are more appropriate for large-scale examinations with adjustable cutoff values. Particular attention is given to high-risk cohorts – employees of carcinogenic hazardous industries – who often present not only with colorectal neoplasms but also with upper gastrointestinal tract pathology. For these individuals, the use of modern immunochemical and molecular genetic technologies is considered appropriate. Objective. To assess the effectiveness and diagnostic value of fecal occult blood tests in the early detection of gastrointestinal pathology in high-risk patients. Materials and methods. From 2021 to 2025, a total of 1,752 employees of an oil refinery in Yaroslavl were examined. At the first stage, three fecal occult blood tests were used: the quantitative immunochemical test FOB Gold Test (iFOBT), the qualitative immunochemical test NADAL iFOB (NADAL), and the Russian qualitative test IHA-FOB-K-FACTOR. At the second stage, expert colonoscopy and esophagogastroduodenoscopy (EGD) were performed to verify neoplastic lesions. Results. A comparative analysis of the three noninvasive fecal occult blood tests revealed the highest diagnostic efficiency for the quantitative immunochemical FOB Gold Test (iFOBT), which demonstrated high sensitivity (up to 85.7 %) and a negative predictive value exceeding 91 %. The qualitative NADAL iFOB showed high sensitivity and a strong positive predictive value, making it effective for screening high-risk patient groups. The IHA-FOB-K-FACTOR test showed low specificity and reproducibility, limiting its clinical applicability. Conclusion. The quantitative iFOBT format provides objective assessment, adjustable cutoff thresholds, and compliance with international colorectal cancer screening standards. Its use is advisable in large-scale preventive programs and for dynamic monitoring of individuals at increased risk, confirming its optimal balance of diagnostic reliability and practical applicability.