Analytical comparison of three quantitative immunochemical fecal occult blood tests for colorectal cancer screening

The superiority of several immunochemical fecal occult blood tests (I-FOBT) over guaiac-based tests in colorectal cancer screening is now established. The aim of this study was to compare the analytical performance of 3 quantitative I-FOBTs.

Stool samples from 10 healthy volunteers, initially I-FOBT negative, supplemented with human blood, were used to compare reproducibility and stability of measurement at varying storage temperatures (4°C, 10°C, 20°C, and 30°C) and durations before test analysis (1 to 10 days) for 3 I-FOBTs (New Hemtube/Magstream HT, OC-Auto sampling bottle3/OC-Sensor DIANA, and FOB Gold/SENTiFOB). Concentrations ranging from 0 to 350 μg Hb/g of feces were evaluated.

The measurement reproducibility of OC-Sensor was superior to Magstream and far superior to FOB Gold. For all tests, variability was essentially related to sampling. Detected hemoglobin (Hb) levels were substantially lower for all tests at temperatures above 20°C. At 20°C, this loss in concentration was less important with OC-Sensor (significant 1.7% daily decrease vs. 7.4% for Magstream and 7.8% for FOB Gold). At 30°C, daily loss was 8.6% with OC-Sensor, whereas after 24 hours, only 30% of the original Hb was detected with FOB Gold, compared to 70% with Magstream. No Hb was detected on day 5 for the latter 2 tests.

About reproducibility and temperature stability, OC-Sensor performed better than Magstream and far better that FOB Gold.

Independently of the chosen test, the delay between sampling and test processing should be reduced, the maximal admissible delay depending on ambient temperature.