Are screening scales for bipolar disorder good enough to be used in clinical practice?

Bipolar disorder is often underdiagnosed. Recommendations for improving the detection of bipolar disorder include the use of screening questionnaires. The most widely studied screening scale is the Mood Disorders Questionnaire (MDQ). Studies of the performance of the MDQ in heterogeneous samples of psychiatric outpatients presenting for treatment have raised concerns about the adequacy of the MDQ as a screening measure because of its relatively low sensitivity. The sensitivity of a scale is not an inherent property of the instrument but depends on the threshold used to identify positive cases. Prior studies used the scoring recommendations of the developers of the MDQ to examine its performance; none examined the performance of the scale across the range of cutoff scores to determine whether a lower threshold would be more appropriate for the purposes of screening. The goal of the present study was to examine the operating characteristics of the MDQ at all cutoff scores to determine the cutoff point that would be appropriate for the purpose of screening. Seven hundred fifty-two psychiatric outpatients were interviewed with the Structured Clinical Interview for DSM-IV, and completed the MDQ. When MDQ caseness was based only on symptom score without regard to level of impairment, the cutoff score associated with at least 90% sensitivity was 5. At this cutoff the specificity of the MDQ was 60.7%, and its positive predictive value was 22.1%. These findings indicate that when the cutoff to identify cases on the MDQ was set to achieve a desired level of sensitivity as a screening instrument most cases screening positive on the scale did not have bipolar disorder. Low positive predictive value does not support the use of the MDQ or any bipolar disorder screening scale in psychiatric clinical practice. (C) 2011 Elsevier Inc. All rights reserved.