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Blood Test Could Help Diagnose Bipolar Disorder

Researchers said they had developed a proof-of-concept blood test to identify biomarkers associated with bipolar disorder as a step towards reducing misdiagnosis.

The condition affects 1.3 million people in the UK, according to Bipolar UK, which said it "takes an average 9.5 years to get a correct diagnosis". Commenting to Medscape News UK, Simon Kitchen, the charity's CEO, described this as a "horrendous wait" and said that a third of people living with the condition reported attempting suicide because of the delay.

For nearly 40% of patients, bipolar disorder was frequently misdiagnosed as major depressive disorder because of overlapping symptoms and the lack of objective diagnostic tools, highlighted the authors of a new study, published in JAMA Psychiatry. "Patients will often only see a doctor when they're experiencing low mood, which is why bipolar disorder frequently gets misdiagnosed as major depressive disorder," underlined first author Dr Jakub Tomasik from the Department of Chemical Engineering and Biotechnology at the University of Cambridge.

The researchers suggested that incorporating biomarker testing could help physicians differentiate between major depressive disorder and bipolar disorder, which not only had symptoms in common, but required different pharmacological treatments.

Enhancing Diagnostic Performance

The most effective way to get an accurate diagnosis of bipolar disorder was a full psychiatric assessment, explained the authors. However, patients often faced long waits to get these assessments, and they took time to carry out.

For the experimental study, the Cambridge researchers set out to identify a reproducible metabolomic biomarker signature that was distinct from major depressive disorder.

The diagnostic analysis, conducted between February 2022 and July 2023, used samples and data from the Delta trial, conducted in the UK between 2018 and 2020. The primary objective was to identify bipolar disorder in patients diagnosed with major depressive disorder within the past 5 years who currently had depressive symptoms. Participants were recruited online through voluntary response sampling.

The researchers used a combination of an online psychiatric assessment and a finger-prick blood test to diagnose patients with bipolar disorder.

Dried blood spot samples were analysed for more than 600 different metabolites using mass spectrometry. Metabolite levels were assessed in 241 patients (mean age 28.1 years, 70.5% female) with depressive symptoms and a recent diagnosis of major depressive disorder. 

Just over one in four (27.8%) participants were subsequently diagnosed with bipolar disorder, and the remainder (72.2%) were confirmed as having major depressive disorder. 

Combining biomarker data with patient-reported information "significantly enhanced" diagnostic performance of models based on extensive demographic data, PHQ-9 scores, and the outcomes from the Mood Disorder Questionnaire, the authors stated, particularly in patients "where the diagnosis was not obvious".

Complementary Approach

The researchers suggested that the blood test on its own could diagnose up to 30% of patients with bipolar disorder but that it was even more effective when combined with a digital mental health assessment.

Dr Tomasik remarked that some patients preferred the biomarker test, because it was an "objective result that they could see".

"The online assessment was more effective overall, but the biomarker test performs well and is much faster," said lead researcher Sabine Bahn, professor of neurotechnology at Cambridge's Department of Chemical Engineering and Biotechnology. A combination of both approaches would be ideal, as they were "complementary", she said.

In addition to having provided a proof of concept for developing an accessible biomarker test, the findings also highlighted the potential involvement of ceramides in the pathophysiological mechanisms of mood disorders, the authors pointed out. They believed this could help researchers understand the biological origins of mental health conditions.

"Psychiatric assessments are highly effective, but the ability to diagnose bipolar disorder with a simple blood test could ensure that patients get the right treatment the first time and alleviate some of the pressures on medical professionals," hypothesised Dr Tomasik.

A blood test to identify biomarkers of bipolar disorder would "open the door" to much earlier diagnosis, prevent deaths, and save the NHS time and resources on "inappropriate and ineffective treatment for misdiagnosed bipolar patients", Mr Kitchen commented.

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