Sensitivity of the suspected blood indicator： An experimental study

AIM： To investigate whether suspected blood indicator （SBI） in capsule endoscopy （CE） is affected by back- ground color and capsule passage velocity. METHODS： Experimental models of the small intestine constructed from paper in a variety of colors were used to simulate the background colors observed in CE im- ages. The background colors studied included very pale yellow, yellow, very pale magenta, light grayish pink, burnt sienna, and deep and dark brown, and red spots were attached inside them. An endoscopic capsule was manually passed through the models. The rate of detection of the red spots by the SBI was evaluated based on the colors of the models and the capsule pas- sage velocities （0.5 cm/s, 1 cm/s, and 2 cm/s）.RESULTS： The rate of detection of the red spots byground color of the model （P 〈 0.001）. Detection rates were highest for backgrounds of very pale magenta, burnt sienna, and yellow, in that order. They were lowest for backgrounds of dark brown and very pale yellow. The rate of detection of red spots by the SBI tended to decrease at rapid capsule passage velocities （1-2 cm/s） compared to slow velocities （0.5 cm/s） for backgrounds of very pale yellow （P = 0.042）, yellow （P = 0.001）, very pale magenta （P = 0.002）, and burnt sien- na （P = 0.001）. No significant differences in the rate of detection were observed according to velocity for light grayish pink （P = 0.643） or dark brown （P = 0.396）. CONCLUSION： SBI sensitivity was affected by back- ground color and capsule passage velocity in the models. These findings may facilitate the rapid detection of bleeding lesions by CE.