Difficulties of risk determination from the use of new contrast media.

The difficulties with comparing data on the risks involved in the use of conventional contrast media and new low-osmolar contrast media are presented. These difficulties are a result of the necessary size of the groups to be compared and the problems of obtaining data. Prospective studies, carried out by a single researcher, probably have the greatest reliability. In multicentered studies with a larger number of participants, a number of factors must be reckoned with. The assessment of the same reaction can vary considerably, depending on the initial illness and interest of the patient or physician. This will, of course, influence the collection of the data. Due to the fact that complications and side effects are more frequent than deaths, the reduction of the first two through the use of new contrast media is statistically easier to ascertain. It can be assumed from the studies performed thus far that the risk of mortality is also reduced. Definite statistical guarantees do not as yet exist, and it is possible that they will never be produced.