Paying attention to ADHD: New biomarker could help curb misdiagnosis

Magnetic field correlation (MFC) indexes of brain iron may represent a noninvasive diagnostic biomarker in the diagnosis of attention deficit hyperactivity disorder (ADHD) and may help parents and physicians make better informed treatment decisions, according to a study published online June 17 by Radiology.

Concerns are increasing over the growing number of children diagnosed with ADHD as they are often treated with psyhostimulant treatment. Lead author Vitria Adisetiyo, PhD, of the Medical University of South Carolina in Charleston, and colleagues investigated brain iron’s ability to be used as a potential noninvasive biomarker for medication-naïve ADHD to prevent misdiagnosis.

During the study, the researchers measured brain iron levels in 22 children and adolescents with ADHD by using an MRI technique known as magnetic field correlation imaging. Of the participants, 12 were considered to be medically naïve as they had never been on medication for their condition while 27 were healthy controls.

Results revealed that the medication-naïve ADHD patients had significantly lower striatal and thalamic MFC indexes of brain iron than the control subjects and psychostimulant-medicated patients.

On the other hand, the MFC indexes in medicated patients were comparable to those in the control subjects.

“These findings implicate reduced brain iron in ADHD pathophysiology before medication that appears to normalize with pyschostimulants,” wrote the authors. “If we consider that psychostimulants reduce ADHD symptoms by predominantly increasing striatal dopamine and that our results parallel previous molecular imaging findings of reduced striatal dopamine biomarkers in medication-naïve ADHD patients and greater dopamine biomarkers in those treated with psychostimulants, brain iron levels in ADHD may indirectly reflect the disrupted dopamine metabolic pathway targeted by psychostimulant treatment.”

No significant differences were observed with the MRI relaxation rates R2, R2*, R2’ or serum measures. According to the authors, these findings suggest that advanced MRI indexes may offer sensitive and more specific brain iron measures than water photon relaxation rates. They also indicate that mechanisms for iron absorption into the brain could be aberrant in ADHD even when serum iron levels are normal.

“We want the public to know that progress is being made in identifying potential noninvasive biological biomarkers of ADHD which may help to prevent misdiagnosis,” said Adisetiyo in a press release. “We are currently testing our findings in a larger cohort to confirm that measuring brain iron levels in ADHD is indeed a reliable and clinically feasible biomarker.”