Application of a Quantitative POCT-FIT Based on Near-Infrared Fluorescence Immunochromatography in Population-Based...

Background/Objectives: Fecal occult blood testing (FOBT) is a cornerstone of colorectal cancer (CRC) screening. The current quantitative FOBTs, however, were centralized, which limited their accessibility in preliminary screening implemented by community health. This study aimed to establish a rapid, highly sensitive quantitative FOB-detection method based on near-infrared fluorescence immunochromatography, hereinafter referred to as point-of-care fecal immunochemical testing (POCT-FIT), and to evaluate its performance against a centralized testing system in population-based CRC screening. Methods: Anti-human hemoglobin monoclonal antibodies were labeled with near-infrared fluorescent nanospheres (excitation 770 nm; emission 794 nm), and FOB test strips were prepared using immunochromatography. A fluorescence immunochromatography analyzer was used to scan the fluorescence intensities of the test line (T) and control line (C). The ratio of the fluorescence intensity on the T-line to that on the C one (T/C) was calculated at different hemoglobin concentrations, and a standard curve was generated over the span of 50 to 2000 ng/mL. A total of 115 clinical fecal samples were collected for methodological comparison with the commercially available OC-Sensor system (Eiken Chemical Co., Ltd., Tokyo, Japan). In a non-paired CRC screening program implemented by community health in Wenzhou, 3163 participants were assigned to the centralized testing group (OC-Sensor system) and 5211 participants to the POCT-FIT group (near-infrared fluorescence immunochromatography method). A positive threshold was set up at 100 ng/mL. Colonoscopy and histopathological results served as the gold standard. Results: The testing results of the two groups for the 115 samples showed that there is a strong linear correlation (R = 0.9959) and good agreement between the two methods. In the screening of community health, CRC prevalence was 2.78% (88/3163) in the centralized group (OC-Sensor) and 1.00% (52/5211) in the decentralized one (POCT-FIT). Sensitivities for CRC were 98.9% (95% CI: 95.8-99.9%) and 100% (95% CI: 93.2-100%), respectively, with no statistically significant difference; specificities were 29.2% (95% CI: 27.6-30.8%) and 27.3% (95% CI: 26.1-28.5%), with the centralized group being slightly higher (p = 0.001). Positive and negative likelihood ratios were comparable between the two methods. Conclusions: The sensitivity of the POCT-FIT method was comparable to that of the OC-Sensor method, and its negative results were associated with a lower probability of missed CRC, which may help reduce medical insurance expenditure for CRC treatment. POCT-FIT is simple to operate and portable, and the price of the disposable immunochromatographic test strip is much lower than that of the turbidimetric method (centralized testing system). Thus, it meets the practical needs of settings with low daily testing numbers (such as preliminary community health or resource-limited and sparsely populated areas) and serves as an effective complement to centralized testing.