A paper published this Tuesday in Translational Psychiatry prompted media claims about the development of the “first blood test to diagnose depression in teenagers.” But psychiatrists say that much more data are needed about the reproducibility and accuracy of the test before it ends up in the clinic.
In the paper, scientists at Northwestern University in Chicago, Illinois, were looking to identify blood biomarkers for early-onset major depression disorder (MDD) in teenagers aged 15–19. They identified a set of 11 genes whose proteins are expressed at low levels in the blood of adolescents with MDD. The genes are involved mostly in neurodevelopment and neurodegeneration.
The scientists, led by psychiatrist Eva Redei, picked candidate biomarkers using two separate rat models that accounted for both the genetic and environmental causes of depression. The genetic profile of their brain and blood samples pointed to 26 candidate biomarkers, which they tested in 28 adolescents, 14 with MDD and 14 controls.
The study is not the first to identify blood biomarkers for MDD. A study published last December developed a diagnostic blood test specifically for MDD. It provided a correct diagnosis 90% of the time using just nine proteins already associated with MDD as biomarkers.
Redei says that her team’s approach with the genomic profiling of rats is part of what makes their study novel. They are the first to find blood biomarkers for MDD using gene expression, rather than proteins, and the first to explore for such biomarkers by looking beyond what is already known about MDD.
“I don’t argue which approach is better,” says Redei. She says that a diagnostic test developed from this study would be only supplementary to the standard means of diagnosis. MDD is now diagnosed by patients reporting their own symptoms.
A blood test would be more objective. It could potentially have less bias than current practice, and provide comfort to adolescents teased by their peers. “Everything is going against this group of adolescents to get better, but if you measure something objectively, someone is less likely to tell you to get yourself together,” says Redei.
Alexander Niculescu, a psychiatrist at the Indiana University School of Medicine in Indianapolis, cautions that “more work needs to be done, and the current level of hype for this study is unwarranted”.
“What is important is to show reproducibility and predictive ability for such tests in independent cohorts of patients, with solid numbers for sensitivity and specificity of the tests. That is the gold standard,” Niculescu says.
The scientists plan to increase the numbers of patients in their future studies, including patients with other psychiatric disorders. They will also compare the results of the blood test before and after treatment to assess whether it can predict response to treatment.
Image of blood tests courtesy of Neeta Lind via Flickr under Creative Commons.