Differentiating borderline personality disorder (BPD) from bipolar disorder: diagnostic efficiency of DSM BPD criteria

Objective We sought to determine the differential diagnostic efficiency of all DSM-IV borderline personality disorder (BPD) criteria by studying a sample of those with BPD and a contrast group with a bipolar disorder (BP). Method Participants were clinically assessed and assigned diagnoses based on DSM criteria - with prevalence rates and diagnostic efficiency values calculated. Results Fifty-three participants were assigned a BPD diagnosis, 83 a BP diagnosis, with comorbid participants excluded. The mean number of DSM BPD criteria assigned was 6.6 (SD = 1.0) in the BPD group and 1.9 (SD = 1.3) in the BP group. The most prevalent criterion in the BPD group was 'affective instability' (AI) (92.5%), with 'inappropriate anger' least endorsed (49%). The highest specificity criterion was 'abandonment fears', which displayed the greatest positive predictive value (PPV) = 0.9, and with AI offering the lowest specificity. 'Unstable relationships' had the highest overall negative predictive value (NPV) = 0.91. The highest percentage accuracy of classification was provided by 'identity disturbance' and 'abandonment fears' criteria, both 85%. Conclusion The transdiagnostic nature of 'affective instability' means it is less useful for diagnostic decisions, whereas 'abandonment fears' and 'identity disturbance' offer superior diagnostic efficiency in distinguishing BPD from BP.