Widely used screening scale may misidentify borderline personality disorder as bipolar disorder

The MDQ is the most widely-used and studied screening tool for bipolar disorder. It is a brief questionnaire that assesses whether a patient displays some of the characteristic behaviors of bipolar disorder. It can be administered by clinicians or taken by patients on their own to determine if they screen positively for bipolar disorder. For the purposes of this study, the MDQ was scored by researchers.

Bipolar and borderline personality disorders share some clinical features, including fluctuations in mood and impulsive actions. The treatments, however, will vary depending on the individual and the diagnosis. Principal investigator Mark Zimmerman, MD, director of outpatient psychiatry at Rhode Island Hospital, conducted a study to test the accuracy of the MDQ.

The research team interviewed nearly 500 patients using the Structured Clinical Interview for Diagnostic Statistical Manual IV (DSM-IV) and the Structured Interview for DSM-IV for personality disorders. The patients were also asked to complete the MDQ. The research team then scored the questionnaires and found that patients with a positive indication for bipolar disorder using the MDQ were as likely to be diagnosed with borderline personality disorder as bipolar disorder when using the structured clinical interview. Further, their findings indicate that borderline personality disorder was four times more frequently diagnosed in the group who screened positive on the MDQ.

Zimmerman says that these findings raise caution for using the MDQ in clinical practice because of how differently the disorders are treated. "An incorrect diagnosis of bipolar disorder will usually lead to a treatment involving medications. If a patient truly has bipolar disorder, that treatment may work. However, at this time there are no approved medications to treat borderline personality disorder.

"Without an accurate diagnosis of borderline personality disorder, we may have many people in treatment who are taking medications that will not work to alleviate the characteristics of the condition from which they really suffer." Zimmerman, who is also an associate professor of psychiatry and human behavior at The Warren Alpert Medical School of Brown University, continues, "In addition, patients with unrecognized borderline personality disorder will not be treated with one of the effective psychotherapies for this condition. It is therefore vital that we develop or identify a more accurate method to distinguish between these two conditions, and adopt it into clinical practice."