Verification of the Storage Stability of Fecal Hemoglobin in Stool Sampling Bottle Using Improved Buffer - A Pilot Study.

OBJECTIVE

The temperature and duration of sample storage is known to affect the accuracy of the fecal immunochemical test (FIT). This study compared an improved stool collection buffer with the conventional buffer on the fecal hemoglobin (Hb) correlation and high-temperature stability and simultaneously evaluated the stability of fecal transferrin (Tf) and fecal calprotectin (FC).

METHODS

From June 2021 to December 2024, 130 stool samples collected from patients with informed consent were analyzed. Fecal Hb, Tf, and FC were measured in samples stored in both buffers, followed by correlation and stability assessments. High-temperature stability was evaluated at 37°C for 1 week.

RESULTS

The improved buffer showed strong correlations with the conventional buffer for three markers (r ≥ 0.95; slope 1.00 ± 0.10). In the high-temperature stability test, residual reactivities were assessed for Hb ≥10 μg/g, Tf ≥10 μg/g, and FC ≥50 μg/g. Hb residual reactivity was significantly higher with the improved buffer (p < 0.01), while Tf maintained high stability (> 90%) in both buffers. FC showed reduced stability in the conventional buffer under prolonged high-temperature exposure, whereas the improved buffer demonstrated better preservation. The improved buffer also maintained higher Hb stability at elevated concentrations (≥30 μg/g).

CONCLUSIONS

The improved stool collection buffer effectively addressed the limitations of the conventional buffer by providing better Hb stability under high-temperature and high-concentration conditions, while preserving excellent stability for Tf and FC. These findings support its potential utility for postal stool collection in FIT-based colorectal cancer screening.