Preliminary evaluation of psychometric properties of the Finnish Borderline Personality Disorder Severity Index: Oulu-BPD-Study.

Background: Borderline personality disorder (BPD) is a severe disorder decreasing the functional ability of the patient and places an extensive burden on the healthcare system. There is a need for a reliable and valid instrument with which unstable recent BPD symptoms can be assessed in a short-term perspective, and which is applicable for clinical evaluations and treatment-outcome research.

Aims: We evaluated the psychometric properties of the Borderline Personality Disorder Severity Index IV (BPDSI-IV) interview in a sample of Finnish BPD patients. Our study is a part of the randomized, monocentre Oulu-BPD trial, which compares the effectiveness of treatment by experts with treatment as usual.

Methods: Patients (n = 71) were enrolled in a 2-year randomized controlled trial. The BPDSI-IV was used to assess recent manifestations of BPD. The internal consistency of the BPDSI-IV in the Finnish patient sample was analysed with Cronbach's alpha coefficient and mean item-total correlation. Discriminant validity was examined by comparing the Finnish BPD patient sample with the Dutch BPD patient and non-patient samples.

Results: The Cronbach's alphas ranged from 0.58 to 0.79 being highest in Dissociation and lowest in Relationships. A total of five subscales out of nine exceeded the acceptable limit (≥ 0.70). With respect to mean item-total correlation, seven out of nine subscales had an acceptable correlation ≥ 0.30.

Conclusions: The BPDSI-IV interview was applied for the first time in a Finnish sample of BPD patients. It appears to be a useful instrument for measuring and following the severity and the change of symptoms of patients with BPD.