Direct comparison of ten quantitative fecal immunochemical tests for hemoglobin stability in colorectal cancer screening

Abstract

Objectives: To systematically investigate and directly compare, for the first time, the sample stability of a large number of quantitative fecal immunochemical tests (FITs) at different storage conditions. Methods: Stool samples were obtained from participants of the German screening colonoscopy program between 2005 and 2010. After an initial FIT-based hemoglobin (Hb) measurement, stool samples were kept frozen at -80°C until analysis. Twenty randomly selected participants with initial measurements ranging from 10 to 100 μg Hb/g feces were included. Ten quantitative FITs were investigated in parallel. A defined stool amount was extracted using each manufacturer's brand-specific fecal sampling device and stored at 5°C, 20°C, and 35°C, respectively. After 1, 4, 5, and 7 days, the samples were analyzed blinded. Median fecal Hb concentrations and positivity rates were calculated. Results: Mean age of the participants was 67 years (range: 56-80 years) and 60% were male. The most advanced finding at screening colposcopy was advanced adenoma in five and non-advanced adenoma in eight cases. Hyperplastic polyps were found in two participants and five participants were without any findings. At 5°C storage temperature, almost all FITs showed fairly stable results throughout the 7-day observation period. At 20°C, most FITs still showed fairly stable results over 4 days, whereas positivity rates significantly declined from day 4 on for most FITs at 35°C. Major differences regarding the sample stability between FITs were observed. Conclusion: FIT-specific Hb decay according to ambient temperature and time period between sampling and test evaluation requires careful consideration in the design of FIT-based screening programs.