Test–Retest Reliability of Self-Reported Reproductive and Lifestyle Data in the Context of a German Case–Control Study on Breast Cancer and Postmenopausal Hormone Therapy

Purpose Studies using survey questionnaires to collect epidemiologic data rely on the accuracy of participantsʹ self-reporting. As part of the quality control protocol for a large population-based case–control study of the association between postmenopausal hormone therapy (HT) and breast cancer in German women (the Mammakarzinom-Risikofaktoren-Erhebung [MARIE] study), the authors used test–retest to evaluate the reliability of womenʹs self-reporting of a number of putative breast cancer risk factors, including HT, reproductive history, family history, and lifestyle. Methods Of those women interviewed between November 2002 and July 2003, 62 cases and 61 controls were re-interviewed an average of 10 months later, using a shortened version of the original study questionnaire. Results Agreement between the first and second interviews was assessed using Cohenʹs κ and proportion of agreement. There was very good overall agreement between the two questionnaires for HT ever/never use (κ = 0.90), type of therapy (κ = 0.83), and form of application (κ = 0.73) and good agreement for duration of use (κ = 0.60). Agreement for other factors ranged from κ = 1.00 for age at first birth to κ = 0.43 for weekend bicycle riding. Agreement was nondifferential by disease status. Conclusions These findings indicate that the MARIE survey instrument was of good quality and had a low likelihood of misclassification.