Well adjusted qualitative immunochemical faecal occult blood tests could be a promising alternative for inexpensive, high-quality colorectal cancer screening

Immunochemical faecal occult blood tests (iFOBTs) have been shown to have higher sensitivity to detect colorectal cancer (CRC) and its precursors than traditional guaiac-based faecal occult blood tests, but are more costly and require specific laboratory equipment. A number of qualitative iFOBTs have been developed, but their performance varied widely because of the large variation in positivity thresholds used for test positivity. We aimed to evaluate the performance of qualitative iFOBTs with well adjusted positivity thresholds in the screening setting. In a study of 229 participants who underwent screening colonoscopy in Germany (45 patients with CRC, 65 with advanced adenoma and 119 free of colorectal neoplasms), we evaluated the performance of two qualitative iFOBTs at five different positivity thresholds and compared it with the performance of a quantitative iFOBT. Receiver operating characteristic curves were constructed. The areas under the curve, and the sensitivity and specificity of the tests, were calculated. For both qualitative tests, sensitivities were around 30% for advanced adenoma and 80% for CRC at very high levels of specificity (98-99%). Comparison of results with the receiver operating characteristic curves for the quantitative test indicated that the qualitative tests yielded similarly high levels of sensitivity at comparable levels of specificity. In conclusion, with appropriate adjustment of positivity thresholds ensuring the levels of specificity required in population-based screening, qualitative, office-based iFOBTs can be an economic, qualitatively comparable alternative to quantitative iFOBTs.