Stable hemoglobin concentration with fecal immunochemical test at high temperatures in a Caribbean colorectal cancer screening program

Background and aims: 

High temperatures may reduce fecal immunochemical test (FIT) positivity and colorectal cancer (CRC) detection sensitivity. We investigated the effect of temperature on hemoglobin concentration [Hb], in the FOB Gold®. Additionally, we examined FIT pick-up, storage, return times and specimen collection. 

Materials and Methods: 

In vitro experiments with buffer containing FIT devices, inoculated with Hb-spiked stool. For 7 days, 144 samples were stored in groups of 36 at 4 °C, 22 °C, 30 °C, and 50 °C. Additionally, 54 samples were stored in groups of 18 at 34 °C, 42 °C and 50 °C for 20 h. Paired t-tests and repeated measure ANOVA assessed [Hb] change. Sixty-five screening participants completed a FIT-handling questionnaire. 

Results: 

After 7 days, mean [Hb] was stable at 30 °C (0.8 µg Hb/g;95 %CI: −1.5 to 3.1;p = 0.50). For 50 °C, mean [Hb] decreased within 2 days (−21.3 µg Hb/g;95 %CI: −30.2 to −12.5;p < 0.001) and after 20 h (−63.0 µg Hb/g;95 %CI: −88.7 to −37.3;p < 0.001), respectively. All other temperature categories showed significant mean [Hb] increase. Same-day FIT return was reported by 80 %. Eighty-seven percent experienced specimen collection as easy and 33 % kept the FIT refrigerated after collection. 

Conclusions: 

The FOB Gold® is suitable for CRC screening in tropical climates. Although most respondents indicated same-day sample return, we recommend avoiding FIT storage above 30 °C for longer than7 days.