Many adults being treated for depression in primary care may have undiagnosed bipolar disorder (BD), suggests a new study

• It’s likely, say the researchers, that many of these patients are receiving antidepressant monotherapy.
• For people who in fact have undiagnosed bipolar disorder, these drugs may be at best unhelpful and at worst harmful.

• BD can be difficult to diagnose and is often misdiagnosed as recurrent major depressive disorder
• A total of 576 (18.5%) agreed to participate and completed 2 screening instruments for BD (the Hypomania Checklist [HCL-32] and the Bipolar Spectrum Diagnostic Scale [BSDS]).
• A total of 370 of them were invited to take part in a one-on-one comprehensive diagnostic and clinical assessment, 154 agreed, and 29 (18.8%) met Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) criteria for BD.
• The researchers generated 3 estimates of the percentage of patients in primary care with a diagnosis of unipolar depression that may, in fact, have unrecognized BD.
• They assumed that all individuals who dropped out of the study by not completing the questionnaire or being assessed did not have BD.
• This seems unlikely and therefore provides an extreme lower bound for the proportion of people with undiagnosed bipolar disorder in this population, the researchers write.
• Their least conservative estimate of 21.6% assumes that all individuals who did not drop out would have responded in the same way as those who were assessed.
• The researchers’ more conservative midestimate of undiagnosed BP in depressed primary care patients is 9.6%.
• Therefore, between 3.3% and 21.6% of primary care patients with depression may have unrecognized BD, Dr. Smith and colleagues note.
• “It’s therefore important,” says Dr. Smith, “that the possibility of undiagnosed bipolar disorder is given greater recognition in primary care, and that GPs [general practitioners] are supported in developing strategies to ensure that their patients with depression receive the correct diagnosis.”
• The findings also suggest that the HCL-32 and BSDS screening questionnaires when used in primary care settings may have “limited utility” in terms of detecting DSM-IV–defined BD.
• The positive predictive values were 50.0% and 32.1%, respectively. However, these instruments may be useful for identifying broader definitions of BD, the researchers say.
• They also found that sub threshold features of BD were relatively common in the cohort of depressed primary care patients and were associated with a more morbid course of illness and greater psychosocial and quality-of-life impairments.
• These findings have important implications for the classification, assessment, and treatment of large numbers of people with depression managed in both primary and secondary care settings.

http://www.medscape.org/viewarticle/738579?src=cmemp