International journal of epidemiology
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The aim of the present study is to investigate the reproducibility of information on sun exposure, skin characteristics and sunburn collected through a standardized questionnaire used in the multi-centre South European case-control study on skin cancer, 'Helios'. We also intended to use results from reproducibility analysis for correcting odds ratio (OR) estimates from the original study. ⋯ Overall, there was good reproducibility, particularly in the case of sun exposure histories, between answers given on two different occasions to a questionnaire administered by trained interviewers. However, since measurement error can substantially bias OR toward the null value, it should be taken into account in estimates of the effect of sun exposure on risk of skin cancer.