An Objective Measure of Attention Helps ADHD Diagnosis

A cognitive test can distinguish among kids with ADHD.

A cognitive, continuous performance test (CPT) can successfully and consistently distinguish among children who have attention deficit/hyperactivity disorder (ADHD). Based on clinical observations and subjective reports, this discovery could improve the validity of ADHD diagnoses.

"There has long been interest in developing objective laboratory-based measures that could support clinical diagnosis," said Itai Berger, MD, The Neuro-Cognitive Center, Hadassah-Hebrew University Medical Center, Jerusalem, Israel, and colleagues.

CPT instruments have shown promise for that purpose, with several measuring selective attention, sustained attention, and impulsivity. Their utility to aid ADHD diagnosis has been debated on several points; however, including whether they have sufficient "ecological validity" to test for attentiveness in the midst of "real world" distractions.

Most CPT instruments present a rapid series of visual or auditory stimuli, with subjects instructed to respond to the "target" stimulus while avoiding responding to the "non-target" or distracting stimuli. Scoring is traditionally based on response time, although this measure has also been criticized for not differentiating between motor speed problems and inattention.

Berger and another of the three investigators serve on the scientific advisory board of NeuroTech Solutions, which produced the CPT, MOXO, named for a term in Japanese martial arts meaning "moment of lucidity". The investigators noted that the instrument had been recently modified to incorporate environmental distractors, and that separate testing had validated its timing index.

The present study to evaluate the usefulness of the MOXO-CPT s a supporting measure in the diagnosis of ADHD was conducted in 339 children with ADHD aged seven to twelve years, and an age-matched control group of 459 without ADHD.

Exclusion criteria included intellectual disability or primary psychiatric diagnosis, and chronic use of medications.

The CPT measured four performance indices: attention, timing, impulsivity, and hyperactivity. The children with ADHD scored statistically significantly lower in the Attention and Timing indices and higher in the Hyperactivity and Impulsivity than the control group.

"That is," Berger and colleagues elaborated, "they (children with ADHD) performed significantly more commission errors from all types: impulsive commission errors — responding to a non-target stimulus as if it was a target stimulus-and hyperactive commission errors that include all other sorts of non-inhibited responses."

The MOXO-CPT total score was found to have the highest correlation with ADHD diagnosis, with an identified cut-off score demonstrating sensitivity rate of 85% or higher across all age categories.

"Integration of CPT indices improves the diagnostic capacity of ADHD and may better reflect the complexity and heterogeneity of ADHD," Berger and colleagues indicate.

The test for validity of the MOXO-CPT, “Usefulness and Validity of Continuous Performance Tests in the Diagnosis of Attention-Deficit Hyperactivity Disorder in Children,” was reported in the February issue of the Archives of Clinical Neuropsychology.

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