The aim of this study was to determining the cut-off for recurrent depressive episode to predict diagnostic conversion from unipolar depression to bipolar disorder by means of retrospective reviews of medical records.

The medical records of 250 patients with a diagnosis of major depressive disorder for at least 5 years were retrospectively reviewed for this study. We reviewed DSM-IV diagnosis and detailed clinical information at the index admission with assessments made every year after discharge to determining the cut-off for recurrent depressive episode to predict diagnostic conversion from unipolar depression to bipolar disorder.

Receiver operating characteristic curve analysis indicated cut-off scores for recurrent depressive episode of more than three times (area under curve = 0.647, sensitivity = 0.435, specificity = 0.819, positive predictive value = 0.351, negative predictive value = 0.865).

These findings suggest that it could predict the best diagnostic conversion from unipolar depression to bipolar disorder when depressive episodes are recurrent more than three times. Based on these findings, it will be able to promote the accuracy of diagnosis and the efficiency of treatment.

The authors have not supplied their declaration of competing interest.