BASIS: the development of a self-report measure for psychiatric inpatient evaluation.

Reliable and valid instruments are vital to assess the course and outcome of psychiatric disorders. This paper describes the development of BASIS (Behaviour and Symptom Identification Scale), a self-report assessment instrument for assessing functioning of psychiatric inpatients, and provides validating data for its use in a psychiatric hospital. The instrument was administered to 677 newly admitted patients. For approximately half of the sample, patients' nearest relatives provided parallel ratings of the patient. Interviews were repeated three to six weeks after admission and again six months after discharge. Test-retest reliability was found to be comparable to that for a standardized symptom checklist (SCL-90). Analyses of validity pointed to the instrument's capability in discriminating diagnostic groups, item correlations with similar symptom dimensions on other assessment measures, and correlations with relative's assessments of patients on the same measure. In conclusion, BASIS appears to be a promising tool for psychiatric inpatient evaluation studies.