LAUSR

BACKGROUND Confusion abounds when differentiating the diagnoses of bipolar disorder (BD) from borderline personality disorder (BPD). This study explored the relative clinical utility of affective instability and self-report personality trait measures for accurate identification of BD and BPD. METHODS Receiver operator characteristics and diagnostic efficiency statistics were calculated to ascertain the relative diagnostic efficiency of self-report measures. Inpatients with research-confirmed diagnoses of BD (n = 341) or BPD (n = 381) completed the Difficulty in Emotion Regulation Scale (DERS) and Personality Inventory for DSM-5 (PID-5). RESULTS The total score for DERS evidenced relatively poor accuracy for differentiating the disorders (AUC = 0.72, SE = 0.02, p < .0001), while subscales of affective instability measures yielded fair discrimination (AUC range = 0.70-0.59). The PID-5 BPD algorithm (consisting of emotional lability, anxiousness, separation insecurity, hostility, depressivity, impulsivity, and risk taking) evidenced moderate-to-excellent accuracy (AUC = 0.83, SE = 0.04, p < .0001) with a good balance of specificity (SP = 0.79) and sensitivity (SN = 0.77). CONCLUSION Findings support the use of the PID-5 algorithm for differentiating BD from BPD. Furthermore, findings support the accuracy of the DSM-5 alternative model Criteria B trait constellation for differentiating these two disorders with overlapping features.