What is the sensitivity of the Fecal Immunochemical Test (FIT)?

Sensitivity of the Fecal Immunochemical Test (FIT)

The sensitivity of FIT for detecting colorectal cancer ranges from 73% to 88%, with a pooled sensitivity of approximately 79% (95% CI, 69-86%) for colorectal cancer detection and a specificity of 94% (95% CI, 92-95%). 1

FIT Sensitivity by Test Type and Cut-off Values

• FIT sensitivity varies considerably depending on the specific brand, cut-off value used, and number of samples collected 1
• When using colonoscopy as the reference standard, the overall sensitivity of one-time FIT screening for colorectal cancer is approximately 77% 1
• The FDA-cleared OC FIT CHEK has demonstrated a sensitivity of 74% and specificity of 96% for cancer detection in a large US study of 9,989 individuals 1
• Quantitative FIT assays can be adjusted by altering the threshold for a positive result - lower cut-off values increase sensitivity but decrease specificity 1

Sensitivity by Cancer Stage and Location

• FIT sensitivity varies by cancer stage, with lower sensitivity for early-stage cancers 2:
  • T1 tumors: 52% sensitivity (95% CI, 37-67%)
  • T2 tumors: 79% sensitivity (95% CI, 68-88%)
  • T3 tumors: 93% sensitivity (95% CI, 89-95%)
  • T4 tumors: 84% sensitivity (95% CI, 72-92%)
• Similarly, for overall cancer stages 2:
  • Stage I cancers: 68% sensitivity (95% CI, 57-78%)
  • Stage II cancers: 92% sensitivity (95% CI, 87-96%)
  • Stage III cancers: 82% sensitivity (95% CI, 73-89%)
  • Stage IV cancers: 89% sensitivity (95% CI, 80-95%)
• FIT has lower sensitivity for proximal colon lesions compared to distal lesions 2

Sensitivity for Advanced Adenomas

• FIT sensitivity for advanced adenomas is significantly lower than for cancer, ranging from approximately 22% to 40% depending on the test and cut-off value 1
• In studies using colonoscopy as the gold standard, sensitivities for advanced adenoma ranged from 25% to 56%, with specificities from 68% to 96% 1
• Decreasing the hemoglobin cut-off value can increase sensitivity for advanced adenomas:
  • In one study, decreasing the OC-Sensor FIT cut-off from 20 to 10 μg/g increased sensitivity from 29% to 35%, with a corresponding decrease in specificity from 97% to 93% 1

Comparison with Other Screening Methods

• FIT has approximately twice the sensitivity of guaiac-based FOBT (gFOBT) for cancer detection (79% vs. 30-65%) 3, 4
• In direct comparisons, FIT consistently demonstrates higher sensitivity than gFOBT:
  • Park et al. found FIT sensitivity for cancer at 84.6% vs. gFOBT at 30.8% 1
  • Parra Blanco et al. found FIT sensitivity for cancer at 100% vs. gFOBT at 54.2% 1
• FIT plus stool DNA testing (FIT-DNA) has higher sensitivity (92%) but lower specificity (84%) than FIT alone 1, 5

Clinical Implications and Pitfalls

• FIT sensitivity varies between different brands and tests, making direct comparisons challenging 1
• The American Gastroenterological Association recommends FIT over gFOBT due to its superior sensitivity 3
• False-negative results are more common with early-stage cancers, potentially missing approximately one-third of stage I colorectal cancers 2
• FIT has poor sensitivity for sessile serrated polyps (approximately 5%), which is an important limitation 3
• Multiple rounds of testing (annual or biennial) can improve cumulative sensitivity over time 1

Practical Considerations

• Sensitivity can be optimized by:
  • Using lower hemoglobin concentration cut-offs (though this reduces specificity) 1, 6
  • Ensuring proper sample collection and handling 3
  • Implementing programmatic annual testing rather than one-time testing 1
• A one-sample FIT at a hemoglobin concentration cutoff of 10 μg/g is significantly more sensitive for advanced adenomas than at higher cutoffs 6