No correlation between Continuous Performance Test and optimal methylphenidate dosage in ADHD children



THE DIAGNOSIS AND treatment of attention-deficit hyperactivity disorder (ADHD) is a clinical decision deriving from thorough developmental history and clinical assessment. For years, scientists have tried to develop an objective and sensitive tool for monitoring drug treatment efficacy in ADHD patients.1

Continuous Performance Test (CPT) is currently the most popular clinic-based measure of sustained attention and vigilance. Studies have confirmed poorer CPT performance in ADHD children, and improved CPT performance after methylphenidate (MPH) treatment.2,3 But CPT offers only modest contributions to the prediction of clinical response of MPH in ADHD.4 Theoretically there would be a positive correlation between CPT and optimal MPH dosage: poorer CPT performance suggests higher optimal MPH dosage. We thus conducted a study to determine whether CPT could predict optimal MPH dosage in ADHD children.

In 2007, 390 children (329 boys, 84.4%; 61 girls, 15.6%), mean age 8.12 ± 1.8 years (range, 6–12 years), who met DSM-IV criteria for ADHD were tested on the CPT before initiation of MPH treatment. Average MPH dosage at remission was 18.2 ± 8.3 mg (range, 5–45 mg). ADHD symptoms were measured with SNAP-IV (Swanson, Nolan and Pelham, version IV).5 Patients were considered to be in remission when scores on the SNAP-IV were only 0 and 1 on ADHD items.

Using the enter method in multiple regression analysis, a significant model emerged (F1,390 = 9.221, P < 0.005; adjusted R2 = 0.047), and only 4.7% of the MPH dosage at remission was accounted for by the patient's chronological age. All performance indices on the CPT were not significantly related to MPH dosage at remission. The hypothesis that there would be a significant positive correlation between CPT and MPH dosage at remission was not supported in these Taiwanese ADHD children.