Reliability, validity, and a total score cutoff for the dyskinesia identification system: condensed user scale (DISCUS) with mentally ill and mentally retarded populations.

The reliability and validity of the Dyskinesia Identification System: Condensed User Scale (DISCUS) are presented for mentally ill (n = 2,822) and mentally retarded (n = 4,649) populations, as are DISCUS item means and standard deviations. A total score cutoff was developed and tested against physician diagnosis and the Research Diagnoses for Tardive Dyskinesia (RD-TD) intensity criterion. DISCUS total score significantly increased as age increased and was significantly greater for 108 TD cases compared to 108 matched no-TD cases. The DISCUS total score of 5 or above was significantly associated with physician TD diagnosis, the RD-TD intensity criterion, and an increasing number of individuals meeting the cutoff score as age increased. Based upon the data, the DISCUS is a reliable and valid TD assessment instrument. It is concluded that the DISCUS cutoff score is as valid a measure of TD as the current operationally defined RD-TD intensity criterion.