British researchers have developed a blood test that may be able to predict whether patients dealing with depression will respond to common drugs used to treat the condition.
If confirmed by larger clinical trials, the test, done on a blood sample drawn from a vein in the arm, could be critically important. That's because about half of all patients dealing with clinical depression don't respond to commonly used antidepressants. And a third of patients don't respond to any of the drugs, making it necessary for healthcare practitioners to try different combinations over time while patients remain without effective treatment.
Because there is no current way to know which patients may respond to which drugs, healthcare practitioners use a trial and error approach and successively try the antidepressants available until they hopefully hit on the right one or the right combination of two or possibly more drugs.
For the new study, published in the International Journal of Neuropsychopharmacology, researchers looked at two biomarkers, both thought to be important because they are involved in several brain mechanisms linked to depression. The biomarkers reflect the presence of inflammation and were found to be strongly associated with treatment response. Earlier studies have found that increased inflammation levels are linked to a poor response to antidepressants.
The researchers measured the levels of macrophage migration inhibitory factor (MIF) and interleukin (IL)-1β in the blood samples of several depressed patients before and after they took a commonly prescribed antidepressant. The researchers found that blood test results above or below a specific threshold can predict the likelihood of patients responding to the treatments.
Patients with levels of MIF and IL-1β above the thresholds showed a 100% chance of not responding to commonly prescribed antidepressants, but those with inflammation below the threshold could be expected to respond to commonly prescribed antidepressants.
"The identification of biomarkers that predict treatment response is crucial in reducing the social and economic burden of depression, and improving quality of life of patients," said Carmine Pariante, MD, Professor of Biological Psychiatry at King's College London and senior author of the study. Instead of waiting weeks to see if an antidepressant will be effective, patients who are predicted to be non-responders could be treated sooner and more assertively with, for example, a combination of antidepressants or anti-inflammatory drugs.
"These results also confirm and extend the mounting evidence that high levels of inflammation induce a more severe form of depression, which is less likely to respond to common antidepressants," said Dr. Annamaria Cattaneo, MD, a psychiatrist at King's College London and the lead author of the study.
So far, the blood test is only at the research stage. Dr. Cattaneo says it's critical to conduct large clinical trials that compare current clinical practices for prescribing depression medication, which is done by trial and error, with an antidepressant treatment plan that is guided by the blood test. Recruitment for that clinical trial has already begun in England.