Among patients eligible for the study , 508 ( 14.8 % ) took a fecal occult blood test after being invited ; 285 ( 15 % ; 95 % confidence interval [ CI ] , 13.5-16 .7 ) in the intervention group and 223 ( 14.6 % ; 95 % CI , 12.9-16 .5 ) in the control group , with no statistical difference between the 2 groups ( odds ratio 1.04 ; 95 % CI , 0.83-1 .31 ; P = .731 ) .