Reliability of clinical judgment of patients' competency to give informed consent: a case vignette study.

The competency of psychiatric patients to give informed consent is important in respecting patients' decisions as well as protecting patients from undue exploitation. A total of 176 members of the Japanese Society of Psychiatry and Neurology gave a clinical judgment in a questionnaire of competency in five case transcriptions. Their interrater reliability of competency judgment was slight (generalized kappa 0.31). Clinicians' global judgment of patients' competency was not reliable, but it may be improved by the use of a structured interview.