Bipolar disorder ‘significantly underdiagnosed’ in primary care
MedWire News: Results from a UK study suggest that a significant proportion of patients treated for depression in primary care may have undiagnosed bipolar disorder.
"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," comment Daniel Smith (Cardiff University School of Medicine) and colleagues.
The team invited 3117 primary care patients from south Wales who were being treated for depression to participate in the current study, of whom 567 accepted.
All of the participants were screened for DSM-IV criteria bipolar disorder using the Hypomania Checklist (HCL-32) and the Bipolar Spectrum Diagnostic Scale (BSDS). Scores of 14 or more on the HCL-32 and 13 or more on the BSDS were used to indicate the presence of bipolar disorder.
All of the participants who scored below these thresholds (n=165) and 50% of those who scored above (n=205) were then invited to take part in a comprehensive diagnostic and clinical assessment. Of these, 154 (41.6%) accepted, including 62 low scorers and 92 high scorers.
The team found that 18.8% (n=29) of the 154 patients who underwent diagnostic and clinical assessment met DSM-IV criteria for bipolar disorder.
The researchers then used the data to make three estimates of how many patients being treated in primary care for depression may have undiagnosed bipolar disorder.
Their most conservative estimate for undiagnosed bipolar disorder among such patients is 3.3%, which is based on the assumption that all of the participants who declined to take part in the study or who did not undergo clinical assessment did not have bipolar disorder.
Their least conservative estimate, based on the assumption that all of those who were not interviewed and all of those who did not return their questionnaires would have responded similarly to those who were interviewed, is 21.6%. The researchers' mid-estimate for undiagnosed bipolar disorder among primary care patients treated for depression is 9.6%.
The researchers also found that the HCL-32 and BSDS had low positive predictive values for bipolar disorder, at 50.0% and 30.1%, respectively.
Smith et al conclude in the British Journal of Psychiatry: "Our findings suggest that a significant minority of primary care patients with a working diagnosis of unipolar depression (between 3.3 and 21.6%) may have an undiagnosed DSM-IV bipolar disorder. Across the UK, this could represent a large number of individuals."
Smith added: "Our findings have real implications for the way in which GPs approach the diagnosis and treatment of patients with depression. We know that many patients with bipolar disorder are not correctly diagnosed for many years.
"It's therefore important that the possibility of undiagnosed bipolar disorder is given greater recognition in primary care, and that GPs are supported in developing strategies to ensure that their patients with depression receive the correct diagnosis."
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By Mark Cowen