Bipolar disorder
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Investigators from the University of Cambridge, reporting their findings today in the journal JAMA Psychiatry, say they have developed a new blood test to help accurately diagnose bipolar disorder. The researchers used a combination of an online psychiatric assessment and the new blood test that identifies biomarkers of the disease to diagnose patients with bipolar disorder, many of whom who had been misdiagnosed with major depressive disorder.

Patients with major depressive disorder and bipolar exhibit many of the same symptoms, but require different pharmacologic treatments, so having a blood test that can help differentiate the two disorders could eventually prove a useful tool for accurate diagnosis as well as help them understand the biological underpinnings of the disease. The researchers note that the blood test on its own could potentially diagnose up to 30% of patients with bipolar disorder, but is more powerful when combined with a psychiatric assessment.

“People with bipolar disorder will experience periods of low mood and periods of very high mood or mania,” said first author Jakub Tomasik, PhD, a senior research associated in the department of chemical engineering and biotechnology at Cambridge. “But 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.”

While only about one percent of the population suffer from bipolar disorder, the misdiagnosis of it as major depressive disorder occurs as frequently as 40% in these patients.

“When someone with bipolar disorder is experiencing a period of low mood, to a physician, it can look very similar to someone with major depressive disorder,” said Sabine Bahn, MD, PhD, a professor of neurotechnology, who led the research from the Bahn lab at Cambridge. “However, the two conditions need to be treated differently: if someone with bipolar disorder is prescribed antidepressants without the addition of a mood stabilizer, it can trigger a manic episode.”

For their work, the Cambridge team used biospecimens and data from the 2018 to 2020 Delta study, conducted in the U.K. to identify patients with bipolar disorder who had received a diagnosis of major depressive disorder within the previous five years and still exhibited symptoms.

More than 3,000 patients were recruited online via voluntary response sampling. Each participant completed a mental health assessment that consisted of more than 600 questions covering topics ranging from relevant mental health disorders including past or current depressive episodes, anxiety, symptoms of mania, family history, and substance abuse.

Roughly one-third of those who completed the assessment were selected to send in a dried blood sample collected via a finger prick. The sample was analyzed using mass spectrometry to help detected more than 600 different metabolites in the blood. After completing the Composite International Diagnostic Interview, a fully structured and validated diagnostic tool to establish mood disorder diagnoses, 241 participants were ultimately included in the study.

The team found that their data identified a significant biomarker signal for bipolar disorder, even after adjusting for other factors, such as medication use. These biomarkers were correlated primarily with lifetime manic symptoms which were later validated in a separate group of patients who received a new clinical diagnosis of major depressive disorder or bipolar disorder during the study’s one-year follow-up period.

The researchers found that the combination of patient-reported information and the biomarker test significantly improved diagnostic outcomes for people with bipolar disorder, especially in those where the diagnosis was not obvious.

“The online assessment was more effective overall, but the biomarker test performs well and is much faster,” said Bahn. “A combination of both approaches would be ideal, as they’re complementary.”

While the combination approach was more effective, Tomasik noted that the patients in the study preferred the blood biomarker test, as it provided objective information. “Mental illness has a biological basis, and it’s important for patients to know it’s not in their mind. It’s an illness that affects the body like any other,” he said.

Bahn added: “In addition to the diagnostic capabilities of biomarkers, they could also be used to identify potential drug targets for mood disorders, which could lead to better treatments.”

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