Sensitivity and specificity of a new bipolar spectrum diagnostic scale

Objective: To assess the sensitivity and specificity of a self-report questionnaire for bipolar disorder, the Bipolar Spectrum Diagnostic Scale (BSDS). Methods: The BSDS was administered to 68 consecutive patients with bipolar illness and 27 consecutive patients with unipolar major depressive disorder. Created by Ronald Pies, it consists of a descriptive story that captures subtle features of bipolar illness, to which patients may assent on a sentence-by-sentence basis. BSDS scores were compared to clinicians' DSM-IV-based diagnoses. Results: Sensitivity of the BSDS was 0.76, approximately equal in bipolar I and II/NOS subjects (0.75 and 0.79, respectively). The BSDS identified 85% of unipolar-depressed patients as not having bipolar spectrum illness. A shift in the threshold of the BSDS resulted in a large increase in specificity (from 0.85 to 0.93), without a significant loss of sensitivity. Conclusions: The BSDS was highly sensitive and specific for bipolar spectrum illness, especially with the amended threshold for positive diagnosis.