Retrospective assessment of self-reported exposure to medical ionizing radiation: results of a feasibility study conducted in Germany.

Background: Exposure to medical ionizing radiation has been increasing over the past decades and constitutes the largest contributor to overall radiation exposure in the general population. While occupational exposures are generally monitored by national radiation protection agencies, individual data on medical radiation exposure for the general public are not regularly collected. The aim of this study was to determine the feasibility of assessing lifetime medical ionizing radiation exposure from diagnostic and therapeutic procedures retrospectively and prospectively within the framework of the German National Cohort study.

Methods: Retrospective assessment of individual medical radiation exposure was done using an interviewer-based questionnaire among 199 participants (87 men and 112 women) aged 20-69 randomly drawn from the general population at two recruitment locations in Germany. X-ray cards were distributed to 97 participants at one recruitment center to prospectively collect medical radiation exposure over a 6-month period. The Wilcoxon-Mann-Whitney test was used to test differences in self-reported median examination frequencies for the variables age, sex, and recruitment center. To evaluate the self-reported information on radiological procedures, agreement was assessed using health insurance data as gold standard for the time period 2005 to 2010 from 8 participants.

Results: Participants reported a median of 7 lifetime X-ray examinations (interquartile range 4-13), and 42% (n = 83) reported having had a CT scan (2, IQR = 1-3). Women reported statistically significant more X-ray examinations than men. Individual frequencies above the 75th percentile (≥15 X-ray examinations) were predominantly observed among women and in individuals >50 years of age. The prospective exposure assessment yielded a 60% return-rate of X-ray cards (n = 58). 16 (28%) of the returned cards reported radiological examinations conducted during the 6-month period but generally lacked more detailed exposure information. X-ray examinations reported for the period for which health insurance data were available provided a moderately valid measure of individual medical radiation exposure.

Conclusions: The assessment of more recent medical examinations seems in the German National Cohort study feasible, whereas lifetime medical radiation exposure appears difficult to assess via self-reports. Health insurance data may be a potentially useful tool for the assessment of individual data on medical radiation exposure both retrospectively and prospectively.