Effect of sample storage temperature and buffer formulation on faecal immunochemical test haemoglobin measurements

Area of Science:

• Clinical Chemistry
• Gastroenterology
• Biochemistry

Background:

• Faecal immunochemical tests (FIT) are crucial for colorectal cancer screening.
• High temperatures can compromise the accuracy of FIT by degrading faecal haemoglobin.
• Existing sample collection buffers may not adequately protect haemoglobin under thermal stress.

Purpose of the Study:

• To evaluate the impact of different buffer formulations (OC-Sensor, Eiken) on FIT sample stability.
• To assess the effect of various storage temperatures (freezer, refrigerator, room temperature, 35°C, 50°C) on faecal haemoglobin readings.

Main Methods:

• FIT samples with initial haemoglobin levels ≥10 µg/g were stored in original and new buffer formulations.
• Storage conditions included freezer, refrigerator, room temperature (22-24°C), 35°C, and 50°C for up to 14 days (or longer at elevated temperatures).
• Reanalysis measured haemoglobin concentration as a percentage of the initial value to determine stability.

Main Results:

• Both buffer formulations maintained haemoglobin stability above 80% in freezer and refrigerator storage.
• The new buffer demonstrated superior room temperature stability, maintaining >80% haemoglobin for 20 days versus 6 days for the original buffer.
• In the new buffer, haemoglobin remained >80% for 8 days at 35°C and 2 days at 50°C.

Conclusions:

• The new buffer formulation offers significantly improved haemoglobin stabilization properties.
• This enhanced stability is particularly evident at temperatures exceeding 22°C.
• The improved buffer formulation can increase the reliability of FIT results in diverse environmental conditions.