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Testing for ADHD

Question

A patient came to see me for an attention-deficit/hyperactivity disorder (ADHD) evaluation, bringing something called a Test of Variables of Attention (TOVA) and requesting a prescription based on this test. I have no information about this test. What is this test and what role, if any, does this have in ADHD evaluations?

Carol Endo, MD

Response from Craig B.H. Surman, MD
Instructor in Psychiatry, Harvard Medical School; Scientific Coordinator, Adult ADHD Research Program, Massachusetts General Hospital, Cambridge, Massachusetts

To date, no neuropsychological tests can reliably identify ADHD. Although cognitive testing demonstrates deficits in some individuals with ADHD, in others it does not. Likewise, individuals who demonstrate challenges with attention or impulsivity (ADHD traits) on cognitive testing may not meet criteria for ADHD. To meet full criteria for ADHD, patients must currently experience at least 6 of 9 inattentive and/or 6 of 9 impulsive/hyperactive traits, and must have demonstrated a long-standing pattern of these challenges since early childhood, causing impairment in 2 or more settings of their life. Note that these criteria do not require that individuals demonstrate deficits during testing.

TOVA is a type of "continuous performance" test in which subjects are asked to respond to target letters and avoid responding to nontarget letters. Some studies suggest some correlation of TOVA performance with ADHD traits in children. In 1 study, TOVA results correctly identified 80% of a sample of 146 children diagnosed clinically with ADHD and 72% of the sample that did not have ADHD.[1] In another study, TOVA results were unable to differentiate between 116 children with ADHD and 51 children with "subclinical" attention/behavior problems.[2] In general, continuous performance tests are sensitive to a variety of cognitive disorders affecting attention, beyond just ADHD.

Information from a TOVA, or other tests of attention, is most useful in the context of a full neuropsychological evaluation. If a patient exhibits poor performance on a TOVA, a comprehensive assessment is still needed to clarify whether the findings reflect ADHD or another etiology.