Feeling down in the dumps? A blood test could soon predict just how bad things are, making it easier to diagnose and treat illnesses such as depression and bipolar disorder.
Until now, there has been no objective way to measure mood, with clinicians having to rely on their own observations and patients鈥� reports. Yet it is often difficult for patients to judge how bad their condition is. As well as giving a definitive answer, objective measurements would also be useful in assessing whether a drug is starting to have the desired effect or not. 鈥淲e can鈥檛 biopsy the target organ,鈥� says Alexander Niculescu, at the Indiana University School of Medicine, Indianapolis. 鈥淎 blood read-out would be great.鈥�
Niculescu and his colleagues took blood samples from 29 people with bipolar disorder. At the time, 13 of them reported being in a very high, or manic, mood, 13 reported a very low mood, while three felt somewhere in between. They scanned the patterns of gene expression in the samples to find out which genes were activated, and focused on those that were active during mania but switched off in depression, and vice versa.
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The team also analysed blood from mice given drugs to induce manic or depressive-like symptoms, compiled a list of genes previously linked to mood disorders, and reviewed post-mortem evidence from people who had suffered from such disorders. Based on these factors, the team scored each gene, forming a panel of the 10 strongest ones. This was used to create a blood test that could discriminate between highs and lows in people with bipolar disorder.
The panel predicted mood with about 80 per cent accuracy in the original group, and with 60 to 70 per cent accuracy when tested in two different groups of patients (Molecular Psychiatry, ). While a clinical test would need to be more accurate, and sensitive enough to discriminate between variations in depressive symptoms, Niculescu says his findings show such a test is at least feasible. 鈥淚t鈥檚 remarkable that there鈥檚 something there at all,鈥� he says. He now plans to undertake a larger-scale prospective study to improve the test.
鈥淭he genetic blood test predicted mood with 60 to 80 per cent accuracy in people with bipolar disorder鈥�
鈥淚t鈥檚 a great paper,鈥� says Akira Sawa at Johns Hopkins University in Baltimore, Maryland, who agrees biomarkers would be an important step forward for clinical psychiatry. But he thinks that measuring blood enzyme levels will ultimately prove more practical than markers of gene expression, as these are already used by many hospitals to diagnose disease.
Of the genes identified by Niculescu, five were associated with growth factors and five with myelin 鈥� the fatty sheath that wraps around nerve cells and speeds up the rate at which they transmit impulses. He points out myelin abnormalities have previously been associated with mental disorders, including schizophrenia. 鈥淚t鈥檚 a common denominator that the brain is not functioning well,鈥� says Niculescu.
