Evaluation of the usefulness of the simultaneous assay of fecal hemoglobin (Hb) and transferrin (Tf) in colorectal cancer screening – for the establishment of the Hb and Tf two-step cutoff assay (HTTC assay)

: Background One of the issues of fecal immunochemical test (FIT) is false-negativity caused by hemoglobin degradation by bacteria. We investigated the usefulness of the transferrin assay, which is stable toward bacteria. Methods The study included 1174 patients who visited our hospital and underwent colonoscopy for some symptoms or for cancer screening. We compared the hemoglobin-transferrin combination assay with the hemoglobin-alone assay using the Discrete Clinical Chemistry Analyzer NS-Plus and 1174 clinical samples. In the combination assay, two hemoglobin cutoff values (a) and (b) and one transferrin cutoff value (c) were set. Cases with values of (a) or more were defined as primary positive and values lower than (b) were defined as negative. Cases with values between (a) and (b) underwent the transferrin assay. Then, cases with values of (c) or higher were defined as secondary positive. All primary and secondary positive cases were defined as positive. Among the combination of cutoff values (a), (b) and (c), we identified Method A exhibiting high specificity and a positive predictive value (PPV), and Method B exhibiting the highest sensitivity. Results In Method A, the sensitivity of colorectal cancer detection increased from 67.3% to 68.2%, the specificity significantly (p = 0.0011) increased from 90.5% to 92.6%, and the PPV increased from 42.9% to 49.6% compared with the hemoglobin-alone assay. In Method B, the sensitivity increased significantly (p = 0.046) from 67.3% to 71.1% and the PPV increased from 42.9% to 44.8%. Conclusions This combination assay showed higher accuracy and effectiveness for colorectal cancer screening.