Letters to the Editor
Improving the Mood Disorder Questionnaire to Detect Bipolar II Disorder
Dear Editor:
The Mood Disorder Questionnaire (MDQ) (1) is a self-assessment screening tool for a broad diagnosis of the bipolar spectrum (that is, bipolar I [BD I], bipolar II [BD II], and bipolar not otherwise specified [BD NOS], according to DSM-IV criteria). It has 13 questions covering hypomania symptoms, clustering of symptoms, and impaired functioning. Its criteria for a diagnosis within the bipolar spectrum are more than 6 positive questions, plus clustering of symptoms, plus moderate-to-severe impairment. Compared with the Structured Clinical Interview for DSM-III-R (SCID), the MDQ had sensitivity of 73% and specificity of 90% for a bipolar spectrum diagnosis in clinical samples (1) and sensitivity of 28% and specificity of 97% in community samples (2). According to the MDQ, community frequency of the bipolar spectrum was 3.4%—a figure similar to that achieved by adding figures reported in the DSM-IV (meaning underdiagnosis of BD II [3,4]). One limitation of the MDQ is the required moderate-to-severe impairment (5). Because hypomania in BD II often shows improved functioning (6,7), the MDQ is biased against BD II and should be improved to better detect it. Using a semistructured interview focusing on past overactivity, clinicians probing for past hypomania found (with high interrater agreement) that BD II was present in approximately 50% of clinical and community samples of subjects with depression (8–11).
This study aimed to test the usefulness of the MDQ in a clinical sample and to modify it to increase its detection of BD II. In a private practice, 101 consecutively remitted outpatients with BD I, BD II, or major depressive disorder (MDD) were given the MDQ during follow-up visits. Soon after, they were interviewed with the SCID-Clinician Version (SCID-CV) (12). The interviewer was blind to MDQ results. Setting and interview methods are reported in detail elsewhere (9,13). There were many more remitted BD (BD I and BD II) than MDD patients because BD patients were followed up more frequently.
Results
According to the MDQ, frequency of BD was 17.8% (n = 18). According to the SCID-CV, frequency of BD I was 16.8% (n = 17), frequency of BD II was 59.4% (n = 60), and frequency of MDD was 23.7% (n = 24). To test whether this big difference in BD frequency observed between the MDQ and the SCID-CV was related to the the MDQ’s impairment criterion, calculations were remade after deleting it. The modified MDQ was called the MDQ7, indicating a cluster of at least 7 positive items. The MDQ7 found 65 cases of BD; of these, the SCID-CV identified 57 (87.8%) as BD (BD 1, 24.2%; BD II, 63.6%) Among the cases not identified by the MDQ7 (n = 33), 18 (54.2%) were classified by the SCID-CV as BD (BD I, 2.8%; BD II, 51.4%).
Using Stata statistical software (14), we studied agreement between the MDQ, the MDQ7, and the SCID-CV. Comparing the MDQ and the SCID-CV for BD I, we found agreement = 79.2%, kappa = 0.27, and P = 0.0029. Comparing the MDQ and the SCID-CV for BD II, we found agreement = 36.6%, kappa = –0.13, and P = 0.9747. Next, we compared the MDQ7 and the SCID-CV for BD I, finding agreement = 49.5%, kappa = 0.16, and P = 0.0031. When we compared the MDQ7 and the SCID-CV for BD II, we found agreement = 58.4%, kappa = 0.11, and P = 0.1172. Then, we compared the MDQ and the SCID-CV for BD (BD I + BD II) and found agreement = 33.6%, kappa = 0.00, and P = 0.4328. Comparing the MDQ7 and the SCID-CV for BD (BD I + BD II), we found agreement = 73.2%, kappa = 0.36, and P = 0.0001. Logistic regression was used to study associations, sensitivity, and specificity. The MDQ was not significantly associated with SCID-CV BD (Odds Ratio = 1.1, z = 0.17, P = 0.866). The MDQ7 was associated with SCID-CV BD (Odds Ratio = 6.1, z = 3.5, P = 0.000), giving a sensitivity of 87.8% and a specificity of 45.7% for predicting SCID-CV BD.
The MDQ had much higher agreement with the SCID-CV for the detection of BD I, compared with BD II, and low agreement for the detection of BD (BD I + BD II). By contrast, the MDQ7 had high agreement with SCID-CV for the detection of BD. Because the MDQ is a screening tool for bipolar spectrum detection (which then needs to be followed by clinical evaluation), sensitivity is more important than specificity. The modified MDQ’s high sensitivity for BD detection (specifically, modified by deleting the impairment criterion) means few false negatives, or few subjects lost for clinical evaluation (which would then lead to the final diagnosis). The high underdetection of BD II by the MDQ can thus be improved by deleting its impairment criterion.
References
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9. Benazzi F, Akiskal HS. Refining the evaluation of bipolar II: beyond the strict SCID-CV guidelines for hypomania. J Affect Disord 2003;73:33–8.
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12. First MB, Spitzer RL, Gibbon M, Williams JBW. Structured clinical interview for DSM-IV axis I
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14. Stata Corp. Stata 7 statistical software. College Station (TX): Stata Corp: 2000.
Franco Benazzi, MD
Forlí, Italy
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