The blood test, which analyzes levels of nine biomarkers, accurately distinguished patients diagnosed with depression from control participants. There were no significant false-positive results.

Developed by Ridge Diagnostics (Research Triangle Park, NC, USA), the test measures levels of 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.

The measurements are combined using a specific formula to produce a figure called the MDDScore, a number from 1 to 100 indicating the percentage likelihood that the individual has major depression. In clinical use the MDDScore would range from 1 to 10.

The initial study included 36 adults who had been diagnosed with major depression at the Massachusetts General Hospital (MGH; Boston, MA, USA), Vanderbilt University or Cambridge Health Alliance (Cambridge, MA, USA) and 43 control participants from St. Elizabeth's Hospital (Brighton, MA, USA).

MDDScores for 33 of the 36 patients indicated the presence of depression, while only 8 of the 43 controls had a positive test result. The average score for patients was 85, while the average for controls was 33. A second replication phase study included 34 patients from the MGH and Vanderbilt, 31 of whom had a positive MDDScore result. Combining both groups indicated that the test could accurately diagnose major depression with a sensitivity of about 90 % and a specificity of 80 %.

A report of the studies was published in the December 2011 journal Molecular Psychiatry.

"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," said George Papakostas, MD, of the MGH department of Psychiatry, lead and corresponding author of the report. "Adding an objective biological test could improve diagnostic accuracy and may also help us track individual patients' response to treatment."

Antidepressant drugs are the most frequently prescribed medication in the United States today where depression strikes over 19 million adults each year–more than coronary artery disease, cancer, or AIDS. Objective biological test information about depression may aid physicians in the differential diagnosis of MDD, the selection of proper treatment, and effective management of their patients.

Related Links:
Ridge Diagnostics
Massachusetts General Hospital
Cambridge Health Alliance