A team of American medical researchers has created a blood test which they say can accurately diagnose depression.
While certain biomarkers have in the past been found to be associated with depression, none has given an accurate diagnosis. Instead, doctors have relied on questionnaires.
"Traditionally, diagnosis of major depression and other mental disorders has been made based on patients' reported symptoms, but the accuracy of that process varies a great deal, often depending on the experience and resources of the clinician conducting the assessment," says Dr George Papakostas of the Massachusetts General Hospital.
"Adding an objective biological test could improve diagnostic accuracy and may also help us track individual patients' response to treatment."
Previous efforts to develop tests based on blood or urine have either been inaccurate or too insensitive.
"The biology of depression suggests that a highly complex series of interactions exists between the brain and biomarkers in the peripheral circulation," says Dr John Bilello of Ridge Diagnostics, which sponsored the study.
"Given the complexity and variability of these types of disorders and the associated biomarkers in an individual, it is easy to understand why approaches measuring a single factor would not have sufficient clinical utility."
The researchers' new test, though, measures levels of nine biomarkers associated with factors such as inflammation, the development and maintenance of neurons and the interaction between brain structures involved with stress response and other key functions.
These measurements are combined to produce a figure called the MDDScore – a number from 1 to 100 indicating the percentage likelihood that the individual has major depression.
In a pilot study, 36 adults who had been diagnosed with major depression, along with 43 control participants, were evaluated. MDDScores for 33 of the 36 patients indicated the presence of depression, while only eight of the 43 controls had a positive test result.
The average score for patients was 85, while the average for controls was 33. Expanding the study indicated that the test could accurately diagnose major depression with a sensitivity of about 90 percent and a specificity of 80 percent.
"It can be difficult to convince patients of the need for treatment based on the sort of questionnaire now used to rank their reported symptoms," says Bilello.
"We expect that the biological basis of this test may provide patients with insight into their depression as a treatable disease rather than a source of self-doubt and stigma. As we accumulate additional data on the MDDScore and perform further studies, we hope it will be useful for predicting treatment response and helping to select the best therapies."