Abstract
Scales used in studies of bipolar disorder have generally been standardized with major depressive or hospitalized manic patients. A clinician rated scale based on a semi-structured interview for persons with bipolar disorder, with comprehensive coverage of bipolar symptomatology, is needed. We report concurrent, divergent and convergent psychometric reliability, discriminant validity and relationship to a measure of overall function for a new psychometric rating instrument. A primarily outpatient sample of 224 subjects was assessed using the Bipolar Inventory of Symptoms Scale (BISS). The BISS total score and depression and mania subscales were compared to the Young Mania Rating Scale (YMRS), the Montgomery Asberg Depression Rating Scale (MADRS) and the Global Assessment of Functioning Scale (GAF). Clinical mood states were also compared using the BISS. The BISS scores demonstrated good concurrent validity, with estimates (Pearson correlations) ranging from 0.74 to 0.94 for YMRS and MADRS and test-retest reliability from 0.95 to 0.98. BISS concurrent validity with the GAF was significant for four clinical states, but not mixed states. The BISS discriminated primary bipolar mood states as well as subjects recovered for eight weeks compared to healthy controls. In conclusion, the BISS is a reliable and valid instrument broadly applicable in clinical research to assess the comprehensive domains of bipolar disorder. Future directions include factor analysis and sensitivity to change from treatment studies.