A FIT Sample for Fecal Occult Blood Tests

With NICE now focusing on the more sensitive and specific Fecal Immunochemical Tests (FIT) for triaging patients with lower gastrointestinal symptoms, it is important to protect hemoglobin in fecal samples (f-Hb) from degradation. With any method, sample integrity is key to the quality of results, so quantitative FIT systems that use a direct sampling method can help improve this.

The HM-JACKarc automated FIT system, distributed in the UK exclusively by Alpha Laboratories Ltd., uses a specimen collection device specially designed to make sampling easy and to prevent f-Hb degradation. The sampling device tube contains a proprietary buffer which stabilizes f-Hb in samples for up to 14 days at ambient temperature (up to 25 °C) or up to 120 days in the fridge (4°C). This has been confirmed in a study by Carroll et al. (Clin Biochem. 2014 Jul;47(10-11):921-39) investigating the performance characteristics of four FIT methods.

In addition, the HM-JACKarc sample probe makes direct collection of fresh feces easy and hygienic for patients, encouraging uptake of the test. The unique dimpled design of the collection probe ensures excess sample is removed and a uniform amount of feces is added to the tube. Patients thus provide a measured amount of sample irrespective of the fecal consistency, which can vary from liquid to hard pellets. Preservation of the fresh f-HB is initiated as soon as the probe is inserted into the tube.

Historically fecal samples have been collected into specimen pots. Research has shown that for guaiac-based fecal testing, hemoglobin degradation is more pronounced in samples collected into a traditional fecal pot, compared to those dried, smeared samples taken directly onto the gFOBT card. In addition, using both qualitative and quantitative Fecal Immunochemical Tests (FIT), it has been found that false negative results could occur when there is a delay in sampling fresh feces into the tubes or onto the cards of FIT collection devices. Direct sampling into FIT tubes can therefore improve the logistics of getting a quality fecal sample from the patient, to the laboratory for analysis.