Validity of the Mood Disorder Questionnaire (MDQ) as a screening tool for bipolar spectrum disorders in anabaptist populations.

The Mood Disorder Questionnaire (MDQ) is an established screening tool for bipolar spectrum disorders (BSD), but has not been validated in diverse populations and the best scoring method remains uncertain. This study assessed diagnostic validity of the MDQ among Anabaptists, an underserved population frequently involved in genetic research. 161 participants completed the MDQ and were diagnosed by a best-estimate final diagnosis (BEFD). Diagnostic agreements between alternate MDQ scoring methods and the BEFD were quantified using Cohen's Kappa (κ), sensitivity (α), and specificity (β). Scoring criteria evaluated included >7 simultaneous symptoms and at least moderate impairment, >7 simultaneous symptoms, with at least mild impairment, >7 symptoms only, with no further requirement, and three novel scoring methods that require >5 symptoms or fewer. Diagnostic agreement varied. The original method proved most specific but had the lowest κ and sensitivity. κ increased with more liberal scoring criteria, reaching a maximum under the lower-threshold symptom methods, with little loss of specificity in the 5-symptom method. Decreasing the symptom threshold below 5 conferred little or no benefit. These results support the diagnostic validity of the MDQ among this Anabaptist sample and suggest that a 5-symptom scoring method may increase diagnostic sensitivity in populations at high risk for bipolar disorder.