Objective: This study was conducted to determine whether the interjudge reliability of the DSM-III-R concept of bizarre delusions could be improved by alternative definitions of the concept.
Method: Twelve raters evaluated 180 delusions of separate psychiatric patients according to the DSM-III-R and two alternative definitions of bizarre delusions.
Results: The kappas for the DSM-III-R definition and for one of the alternative definitions were 0.64 and 0.65, respectively; for the other alternative definition it was 0.45. All three definitions were highly intercorrelated, largely identifying the same cases.
Conclusions: Neither of the alternative definitions of bizarre delusions was more reliable than the DSM-III-R definition. The reliability of the DSM-III-R definition, although only fair, is comparable to that of other important clinical concepts that play a major role in the DSM-III-R diagnostic criteria for psychotic disorders.