Bipolar primary care prevalence varies by assessment method

By Sara Freeman, medwireNews Reporter

The prevalence of bipolar disorder in primary care varies considerably according to the assessment method used, study findings suggest.

“[B]ipolar screening measures find higher percentages of patients with positive screens for bipolar disorder compared to studies that diagnose bipolar disorder using structured interviews,” Joseph Cerimele (University of Washington School of Medicine, Seattle, USA) and colleagues report in General Hospital Psychiatry.

The researchers performed a systematic review of the literature and identified 15 studies that had examined the prevalence of bipolar disorder in primary care populations. Of these, 12 had used structured interviews and three the Mood Disorder Questionnaire (MDQ) to make the diagnosis of bipolar disorder, bipolar spectrum illness, or identify prior history of mania.

Structured interview instruments used included the Mini International Neuropsychiatric Interview (MINI), the Primary Care Evaluation of Mental Disorders (PRIME-MD), the Diagnostic Interview Schedule (DIS), the Clinical Interview schedule, the Present State Examination 9th Version, and a 79-item questionnaire in addition to a clinical examination by a psychiatrist.

Ten out of 12 studies that used the structured interviews reported a bipolar disorder prevalence of 0.5–4.3%. The two remaining studies found a prevalence of 9.3% and 11.4%, respectively. Differences in the classification of bipolar disorder used and study populations are likely to account for these higher estimates, the researchers suggest.

Using the MDQ to screen patients for bipolar disorder gave a prevalence of 7.6–9.8%. “The higher percentages found in screening studies is likely due to the low positive predictive value of the MDQ in primary care, which translates into a high number of false-positive results,” Cerimele and co-workers comment.

They note: “It is important to have an estimate of bipolar prevalence in primary care because knowledge of disease prevalence can influence accurate disease recognition.”

The authors explain that one of the problems with recognizing bipolar disorder is that it can take a decade between the onset of symptoms and a diagnosis being made. Better, earlier recognition in primary care could perhaps lead to improved treatment, the team suggests, an approach that has already worked for major depression and anxiety disorders in the past.

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