A New Faecal Immunochemical Test Buffer With Improved Haemoglobin Stability Under Varying Temperature and Storage Times

BACKGROUND: Measurement of faecal haemoglobin (f-Hb) using the faecal immunochemical test (FIT) in population screening for colorectal cancer (CRC) has reduced cancer-related incidence and mortality. However, temperature-induced f-Hb degradation can decrease FIT accuracy. This study assessed the f-Hb preservation capacity of a new FIT Hb-stabilising buffer at different temperatures and durations. METHODS: Fresh whole faecal samples from individuals with active colorectal bleeding were used for collection of samples using the OC-Sensor FIT (EIKEN CHEMICAL CO. LTD, Japan) containing either the standard (SOC3) or new formulation (SOC4) buffer. Pooled faeces-buffer mixtures (n = 29) were divided into aliquots for incubation at 4°C, 23°C, 35°C, 45°C, and 50°C and analysed for f-Hb concentration at days 0, 3, 7, 10, 14, 21, and 28. Relative f-Hb (percentage change of day 0) in both buffer types was compared between temperatures at each timepoint. Generalised linear modelling identified variables influencing f-Hb degradation. RESULTS: SOC3 exhibited significant f-Hb decline from day 10 at 23°C and from day 3 at all higher temperatures assessed (p < 0.05). In contrast, f-Hb concentrations remained stable within SOC4 for up to 28 days at 23°C, with reductions observed after 7, 7, and 14 days at 50°C, 45°C, and 35°C, respectively (p < 0.05). Higher temperatures and longer storage duration significantly decreased f-Hb concentration, while SOC4 demonstrated superior f-Hb preservation relative to SOC3 (generalised linear model estimate = 15.4, p < 0.001). CONCLUSION: The SOC4 FIT buffer improves f-Hb stability compared with the current formulation and may improve CRC screening accuracy, particularly in high-temperature environments.