[Can we know the frequency of true late adverse reactions to nonionic contrast media?: Late adverse reactions due to factors other than contrast media].

We investigated the frequency and causative factors of symptoms unrelated to contrast media (false late adverse reactions) among patients who were evaluated as having late adverse reactions to contrast media. The nature and frequency of complaints stated by each 200 of patients who underwent plain CT scans and enhanced CT scans were evaluated. In the plain CT group, three patients showed false late adverse reactions. The frequency was 2.6% among respondents and 1.5% in the population. These symptoms encompassed psychological effects and diseases that developed after CT scanning. It is difficult to detect only true late adverse reactions, because of survey bias.