PRE-ANALYTICAL FAECAL STORAGE CONDITIONS IN THE DIAGNOSIS OF COLORECTAL CANCER

Background: The detection of the fecal occult blood represents a fundamental step in making an early diagnosis of colorectal cancer and the pre-analytical storage conditions of samples must to be accurately standardized. The aim of the present study was to compare the stability of hemoglobin in feces collected with two sampling devices specific for the fecal immunochemical tests, FOB Gold Tube Screen (SCREEN) and OC-Sensor DIANA (OC) respectively. Materials and methods: 15 true positive fecal samples were collected with both devices. A pool from each sample was made, portioned and stored at + 4°C, + 21°C and + 32°C for 10 days. One aliquot of each pool stored at the specified temperatures was tested at five time intervals between sampling and analysis (1, 3, 6, 8 and 10 days). Results: The percentage of cumulative fecal hemoglobin decrease (HbCD%) has been evaluated. At + 4 C, HbCD% was lower in pool collected using OC in comparison to that observed using SCREEN devices (p = 0.05), being maximum HbCD% equal to 10.3% observed 10 days after collection using OC device in comparison to 18.8% in samples collected using SCREEN device. No significant difference between collection devices (p = 0.06 and p = 0.83 respectively) were found for sample stored at + 21°C and + 32°C. Conclusion: At + 4°C OC preserves the fecal hemoglobin better than SCREEN device, while at room and high temperatures, the devices demonstrated comparable storage performance. The refrigerate temperature represents the more suitable condition for fecal sample storage, although the hemoglobin degradation occurs immediately from the first day after collection. Therefore the delivery of fecal samples to the laboratory must to be done as soon as possible.