Bipolar diagnosis in China: Evaluating diagnostic confidence using the Bipolarity Index

Background: Diagnosis of bipolar disorder is inherently difficult. The goal of this study was to examine the utility and psychometric properties of the Bipolarity Index (BPx) in a population of patients treated in China.

Methods: At nine Chinese health facilities participating in CAFÉ-BD, clinicians completed a standardized affective disorder evaluation for consecutive patients (N=615) with a clinical diagnosis of MDD and BPD and scored the Bipolarity Index. The investigators constructed ROC curves to determine the optimal cut off points to discriminate subjects in three clinical diagnostic groups: bipolar disorder (BPD), major depressive disorder (MDD) and healthy (no psychiatric diagnosis) controls (HC). This study is registered with ClinicalTrials.gov, number NCT02015143.

Results: 1) The cut-off score between the MDD and BPD groups was 42.0, with a sensitivity of 0.957 and specificity of 0.881 (Z=63.064, P<0.001); the cut-off score between the MDD and BPD II groups was 34.0, with a sensitivity of 0.810 and specificity of 0.855 (Z=20.174, P<0.001); and the cut-off score between the BPD II and BPD I groups was 57.0, with a sensitivity of 0.680 and specificity of 0.772 (Z=9.636, P<0.001). 2) Five domains contributed to the discrimination results. State-related domains (episode characteristics and course of illness) made greater contributions than trait-related domains (age of onset, family history, and treatment response).

Limitations: The data are purely descriptive. The BPD II sample and the family history dataset were small.

Conclusions: Our finding indicates good reliability and validity for the Chinese version of the BPx, which encourages its use as a measure of diagnostic confidence for bipolar spectrum disorders. Further prospective study is necessary to determine if the BPx is useful in identifying subgroups among MDD subjects at high risk for conversion to BPD.