Optimal cut-off value for detecting colorectal cancer with fecal immunochemical tests according to age and sex

In the fecal immunological test, a suitable cut-off value may be selected to classify results as either positive or negative. Our aim is to estimate the optimal cut-off value for detecting colorectal cancer in different age and sex groups. This is a multicentric retrospective cohort study of participants in CRC screening programs with FIT between 2006 and 2012. A total of 545,505 participations were analyzed. Cancers diagnosed outside of the program were identified after a negative test result (IC_test) up until 2014. The Wilcoxon test was used to compare fecal hemoglobin levels. ROC curves were used to identify the optimal cut-off value for each age and sex group. Screening program results were estimated for different cut-off values. The results show that the Hb concentration was higher in colorectal cancer (average = 179.6 mu g/g) vs. false positives (average = 55.2 mu g/g), in IC_test (average = 3.1 mu g/g) vs. true negatives (average = 0 mu g/g), and in men (average = 166.2 mu g/g) vs. women (average = 140.2 mu g/g) with colorectal cancer. The optimal cut-off values for women were 18.3 mu g/g (50-59y) and 14.6 mu g/g (60-69y), and 16.8 mu g/g (50-59y) and 19.9 mu g/g (60-69y) for men. Using different cut-off values for each age and sex group lead to a decrease in the IC_test rate compared to the 20 mu g/g cut-off value (from 0.40 parts per thousand to 0.37 parts per thousand) and an increase in the false positive rate (from 6.45% to 6.99%). Moreover, test sensitivity improved (90.7%), especially in men and women aged 50-59y (89.4%; 90%) and women aged 60-69y (90.2%). In conclusion, the optimal cut-off value varies for different sex and age groups and the use of an optimal cut-off value for each group improves sensitivity and leads to a small decrease in IC_tests, but also to a larger increase in false positives.

Automated summary

The study on fecal immunological tests indicates that selecting optimal cut-off values for different age and sex groups can improve colorectal cancer screening sensitivity, reduce the need for further testing after negative results, but also lead to an increase in false positive diagnoses.