Case 9: CRC Screening Tests

Think again. gFOBT is not recommended by ACG, Although prior randomized control trials show a reduction in CRC incidence and mortality with annual FOBT, fecal immunochemical test (FIT) has now replaced gFOBT since it does not require a restricted diet before testing and since it is more specific for blood loss from the lower gastrointestinal tract. 

Great choice. FIT is recommended by the ACG as a primary, non-invasive, screening modality. It is non-invasive and can be done at home without any bowel preparation. It is highly specific (> 94%), though with lower sensitivity (79%) for advanced adenomas and it does not detect serrated lesions.

Reasonable option for a non-invasive test that can be done at home without any bowel preparation. mtDNA test can be considered if a patient is unable or unwilling to undergo colonoscopy or FIT. While more sensitive (>92%) than FIT for advanced adenomas and serrated polyps, it is less specific (87%) than FIT and therefore results in more false positive tests. Furthermore, the long-term reduction in CRC incidence and mortality is unknown.

Think again. Colon capsule can be considered if a patient is unable or unwilling to undergo colonoscopy or FIT, however it has lower sensitivity (81%) and specificity  (93%) for CRC than both FIT and mtDNA testing. Though minimally invasive and can be done at home, bowel preparation is still required. Additionally, it is not recommended by the USPSTF.

Think again. CT A/P is not a screening modality recommended by either the ACG or USPSTF.

Reasonable option. CT colonography can be considered if a patient is unable or unwilling to undergo colonoscopy or FIT. It has high sensitivity (90-100%) for CRC but variable sensitivity for polyps and poor sensitivity for flat lesions and sessile serrated lesions. While less invasive than colonoscopy and without the need for sedation, bowel preparation is still required.

Reasonable option. Flexible sigmoidoscopy can be considered if a patient is unable or unwilling to undergo colonoscopy or FIT. It provides a long-term reduction of 21% in CRC incidence and 26% reduction in mortality. It is also highly sensitive (90-100%) for distal colon lesions, but it cannot visualize the entirety of the colon, requires enemas for preparation and is an invasive test option.

Think again. Septin 9 is a blood based methylated DNA test with an unknown incidence or mortality benefit and low sensitivity (48%) for CRC detection. It is not recommended by either the ACG or USPSTF.