RELIABILITY OF DATA ON SMOKING HABIT AND COFFEE-DRINKING COLLECTED BYPERSONAL INTERVIEW IN A HOSPITAL-BASED CASE-CONTROL STUDY

A study on the reliability of information on smoking habits and coffee drinking collected via interview was conducted among 500 subjects enr olled in a case-control study on bladder cancer in Brescia, North Ital y. A total of 215 cases (incident and prevalent) and 285 controls were interviewed personally in the hospital setting by a first interviewer , and then reinterviewed by telephone by either the same interviewer o r another one. Agreement between the first and second interview was ev aluated using the kappa statistic and the intra-class correlation coef ficient and via multiple logistic regression modelling. No important d ifferences in reliability were found according to sex, education or ca se/control status, while agreement was better among subjects below 65 than among older ones, and among incident than prevalent cases. A slig htly better agreement was found among subjects interviewed twice by th e same interviewer than those interviewed by two different individuals , which may reflect the presence of inter-observer reliability for the latter. Overall, these results show a very high reliability of data o n smoking and a fairly high reliability regarding coffee drinking as c ollected through face-to-face interviews.