経鼻内視鏡スクリーニングにおける胃癌偽陰性の検討

A Retrospective Single-center Study on False Negative Cases of Gastric Cancer Screening with Transnasal Ultrathin Endoscopy in Japan

要旨　経鼻内視鏡による胃癌スクリーニングの精度について，人間ドック健診を専門とする当施設の成績を検討した．（1）胃癌発見率は経鼻内視鏡群のべ17,205人中0.23％，通常径内視鏡群のべ15,305人中0.22％と差を認めなかった．（2）経鼻内視鏡検診で診断された胃癌39例のうち，“発見から遡り3年以内に経鼻内視鏡検診で胃癌なしと診断された症例”を偽陰性と定義すると11例が該当した．偽陰性率は28.2％，画像見直しで前回は指摘困難と考えた2例を除くと23.1％であった．これらの結果は通常径内視鏡での検討を含めた諸家の報告と大差なく，経鼻内視鏡は胃癌発見率および偽陰性率の点でも有用と考える．

　We examined 17,205 cases of gastric cancer screening health checkups with transnasal ultrathin endoscopy from April, 2005 through August, 2011, and 39 cases of gastric cancer were detected. The gastric cancer detection rate was 0.23％, which is not inferior to our previous result（0.22％ in 15,305 cases）using a regular-sized oral endoscope. Among them, we defined eleven cases, who had undergone transnasal endoscopic screening at our institute within three years before the detection of gastric cancer, as false negative cases. Compared to the previous screening endoscopic images, we retrospectively determined that 8 of these cases had been overlooked or poorly examined, 2 cases were difficult to detect, and 1 case might have been missed by a poor biopsy specimen. The false-negative rate was 28.2％（11/39）, and if we eliminate the 2 difficult-to-detect cases, the rate would be 23.1％. The results were similar to those reported by others using a regular-sized oral endoscope, thus, we conclude that transnasal ultrathin endoscopy is useful and is not inferior to regular-sized oral endoscopy for gastric cancer screening.