Quantification of Self Selection Bias in Mass-screening for Gastric Cancer

Abstract

Self selection bias in mass-screening for gastric cancer was quantified using data from a group consisting of 66, 386 workers. Total observed person-year was 182, 779. Among males self selection bias was thought to exert some influence that made the incidence rate about 1. 13(all ages, 95%CI=0.65-1.97) or 1.23(over 40, 95%CI= 0.69-2.20)-fold higher and the mortality, rate about 1.22(all ages, 95%CI=0.48-3.13) or 1.42(over 40, 95%CI=0.54-3.69)-fold higher in the screening-attending group. Among females self selection bias was thought to exert some influence that made the incidence rate about 0.30(all ages and over 40, 95%CI=0.04-2.47 and 0.04-2.48)-fold lower and the mortality rate about 1.09(all ages, 95%CI=0.18-6.68) or 1.11(over 40, 95%CI=0.18-6.76)-fold higher in the screening-attending group. J Epidemiol, 1991 ; 1 : 7-10.