Researchers have found substantial variations in the performance characteristics of five commonly used fecal immunochemical tests (FIT), according to a recent study published by Levy et al in the Annals of Internal Medicine.
Background
Stool-based tests like FIT are currently recommended for colorectal cancer screening because they are convenient, safe, and can be performed at home without dietary restrictions. However, some FIT tests have higher rates of unusable results.
FIT tests with lower sensitivity could miss more patients with colorectal cancer and advanced polyps, whereas tests with higher sensitivity and lower positive predictive value may require more colonoscopies to identify patients who need treatment.
Study Methods and Results
In a comparative study, the researchers recruited 3,761 patients who underwent five different FIT tests prior to colonoscopy. They examined the performance characteristics of the tests with the goal of evaluating how well each test could detect advanced colorectal neoplasia—which includes advanced polyps or colorectal cancer.
Four of the tests were qualitative, giving a positive or negative result, while one of the tests was quantitative, providing a numerical measure of blood in the stool. The researchers measured each test's sensitivity and specificity, along with other factors such as how often the tests provided unusable results. They also analyzed which factors influenced the tests' ability to detect advanced colorectal neoplasia.
The researchers discovered that substantial variations in the FIT tests’ performance characteristics. They noted that the brand of the tests was the most important factor affecting sensitivity. Additionally, sensitivity was greater in the patients with a higher body mass index and those with lower income. The researchers suggested that this may have been because the FIT test was one of their initial screenings. There was greater sensitivity in those with distal adenomas. Notably, the FIT tests were less sensitive in female patients, likely because of the higher prevalence of proximal lesions.
Conclusions
The researchers underscored that the findings may have implications for the benefits and cost-effectiveness of colorectal cancer screening using FIT testing.
Disclosure: For full disclosures of the study authors, visit acpjournals.org.
