Evaluation of a desk top instrument for the automated development and immunochemical quantification of fecal occult blood

Background: The guaiac fecal occult blood test (FOBT) for colorectal cancer (CRC) screening is user dependent and not specific for human hemoglobin (Hb). The automated-developed, quantitative, immunochemical human Hb FOBT (I-FOBT) is specific, allows for quality control and selection of a suitable Hb level, with optimal sensitivity and specificity, for colonoscopy. Material/Methods: We evaluated a desktop instrument, OC-MICRO™ (Eiken, Japan), which automatically develops and quantifies 50 fecal tests/hr for Hb; for ease of use, test reproducibility and stability and intrapatient daily I-FOBT variation; clinical evaluation included sensitivity and specificity for neoplasia in patients undergoing colonoscopy. Results: Five hundred patients prepared 3 fecal tests which were quantified for Hb, I-FOBT samples were: (1) repeatedly re-examined; (2) stored at 4°C or 20°C or 28°C and re-examined; (3) I-FOBT levels correlated with colonoscopic findings. Five I-FOBTs re-examined 6 times had no significant changes; 30 tests stored ≥21 days had a decay/day of: 0.3%±0.4 at 4°C (NS), 2.2%±1.7 at 20°C (NS) and 3.7%±1.8 at 28°C (P<0.05). Receiver operator characteristic curve analysis showed that at the 100 ng Hb/mL I-FOBT level 76.5% of CRCs and advanced adenomas were detected with a specificity of 95.3%. Conclusions: The instrument provided reproducible results and refrigerated I-FOBT samples were stable 21 days. An I-FOBT level can be chosen to provide optimal sensitivity and specificity for significant neoplasia.