Screening for bipolar disorder in medicated patients treated for unipolar depression in a psychiatric outpatient clinic using the Mood Disorder Questionnaire.

Objective. The aim of this study was to examine the rate of the misdiagnosis of bipolar disorder in outpatients who had been treated for unipolar depression with antidepressants in Taiwan and to verify the validity of the Mood Disorder Questionnaire (MDQ) in this population. Method. Fifty-three outpatients who had been treated for unipolar depression were recruited. All patients completed the MDQ and were administered the Structured Clinical Interview. The sensitivity and specificity were calculated for each possible MDQ symptom cut-off score relative to a Structured Clinical Interview diagnosis of bipolar spectrum disorder. Results. A total of 11.3% were diagnosed with bipolar spectrum disorder. The optimal model we found contained only the first portion of the MDQ with a cut-off score of 2. This model provided both good sensitivity (0.83) and specificity (0.53). Conclusion. The misdiagnosis of bipolar disorder as unipolar depression disorder is prevalent. Based on the results of the current study, the probability of bipolar disorder in depression outpatients who are in a mildly depressed state and score higher than 2 points in the first portion of the MDQ deserves to be investigated.