The optimal cut‐off value in fit‐based colorectal cancer screening: An observational study

Background Colorectal cancer (CRC) screening programs using fecal immunochemical test (FIT) have to choose a cut‐off value to decide which citizens to recall for colonoscopy. The evidence on the optimal cut‐off value is sparse and based on studies with a low number of cancer cases. Methods This observational study used data from the Danish Colorectal Cancer Screening Database. Sensitivity and specificity were estimated for various cut‐off values based on a large number of cancers. Traditionally optimal cut‐off values are found by weighting sensitivity and specificity equally. As this might result in too many unnecessary colonoscopies we also provide optimal cut‐off values for different weighting of sensitivity and specificity/number of needed colonoscopies to detect one cancer. Results Weighting sensitivity and specificity equally gives an optimal cut‐off value of 45 ng Hb/ml. This, however, means making 24 colonoscopies to detect one cancer. Weighting sensitivity lower and for example, aiming at making about 16 colonoscopies to detect one cancer, gives an optimal cut‐off value of 125 ng Hb/ml. Conclusions The optimal cut‐off value in an FIT population‐based screening program is 45 ng Hb/ml, when as traditionally sensitivity and specificity are weighted equally. If, however, 24 colonoscopies needed to detect one cancer is too huge a burden on the health care system and the participants, 80, 125, 175, and 350 ng Hb/ml are optimal cut‐off values when only 19/16/14/10 colonoscopies are accepted to find one cancer.
If 24 colonoscopies needed to detect one cancer is acceptable for the health care system and the participants, the optimal cut‐off value in fecal immunochemical test screening is 45 ng Hb/ml. When only 19/16/14/10 colonoscopies are accepted to find one cancer, then, the optimal cut‐off value is 80/125/175/350 ng Hb/ml.