間接X線胃集検における偽陰性例の特徴

Characteristics of False Negative Cases in Gastric Cancer Mass Survey

要旨　間接X線胃集検における偽陰性例（率）を分析し検討した結果，次のような結論となった．①間接X線の偽陰性率は経年的に高くなってきているが，その要因は受診者の固定化現象により早期癌の占める割合が多くなってきているためと考えた．①間接X線の進行癌偽陰性率を前期（1982年度）と後期（1987年度）で推計してみると，前期31.3％から後期24.2％へ減少しており，この結果は間接X線撮影法の改正による示現能が向上したためと推察した．①進行癌偽陰性例を調べてみると，癌型では早期類似型が多く，部位では小彎側に集中しており，特に幽門輪近傍と噴門部領域で多い傾向がみられた．①進行癌偽陰性例の中に発育の速いものがあり，癌の自然史，特に時間的因子も関与していると思われた．①進行癌偽陰性例の5年相対生存率は61.1％であり，集検初回群の5年相対生存率と比べて予後が良好であった．

　False negative cases in gastric cancer mass survey were examined to determine the diagnostic capability of indirect roentgenography as a primary screening method.

　In the present study, we defined "false negative" case as follows; the case in which no abnormal finding had been obtained in a gastric mass survey proved to have cancer within one year by investigative report or cancer registration. The subjects were those covered by the mass screening method of Miyagi cancer society in 1987. Among 178,115 individuals who underwent gastric mass survey, stomach cancer was found in 310 cases and overlooked in 130 cases (i.e., false negative). Thus, the total number of the cases of stomach cancer at the time of mass survey was estimated to be 440.

　The result was that 70.4% for sensitivity,90.1% for specificity,9.9% for false positive rate and 29.8% for false negative rate. There was a case of early stage cancer among false negatives. The 5-year survival rate for these false negative cases was 66.1%.