Evaluating medication response in ADHD: cognitive, behavioral, and single-subject methodology

Analyzing Digit Span Components for Assessment of Attention Processes

The Digit Span (DS) subtest of the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) is thought to be a measure of attention, concentration, sequencing, number facility, and auditory short-term memory. An optional WISC-III subtest and part of the Freedom from Distractibility (FD) factor, DS assesses several cognitive constructs, yet its utility in differential diagnosis has been questioned because poor DS or FD performance has been inconsistently associated with attention processes. In this study of 195 children referred for comprehensive neuropsychological evaluations, Digits Forward (DF) and Digits Backward (DB) component scores were found to be differentially predictive of attention, executive function, and behavior rating measures. Results suggest that DB is associated with attention and executive function processes, not the short-term rote auditory memory processes tapped by DF.

The effects of methylphenidate on cognitive function in children with attention-deficit/hyperactivity disorder

Focusing on behavioral criteria for attention-deficit/hyperactivity disorder (ADHD) diagnosis leads to considerable neuropsychological profile heterogeneity among diagnosed children, as well as variable response to methylphenidate (MPH) treatment. Documenting "cold" executive working memory (EWM) or "hot" self-regulation (SR) neuropsychological impairments could aid in the differential diagnosis of ADHD subtypes and may help to determine the optimal MPH treatment dose. In this study, children with ADHD inattentive type (n = 19), combined type (n = 33), and hyperactive-impulse type (n = 4) underwent randomized controlled MPH trials; neuropsychological, behavioral, and observational data were collected to evaluate the children's responses. Those with moderate or significant baseline EWM/SR impairment showed robust MPH response, whereas response for those with lower baseline impairment was equivocal. Implications for medication use and titration, academic achievement, and long-term treatment efficacy are examined.

Early identification of stimulant treatment responders, partial responders and non-responders using objective measures in children and adolescents with hyperkinetic disorder

BACKGROUND

  The aim of this study was to evaluate stimulant medication response following a single dose of methylphenidate (MPH) in children and young people with hyperkinetic disorder using infrared motion analysis combined with a continuous performance task (QbTest system) as objective measures. The hypothesis was put forward that a moderate testdose of stimulant medication could determine a robust treatment response, partial response and non-response in relation to activity, attention and impulse control measures.

METHODS

  The study included 44 children and young people between the ages of 7-18 years with a diagnosis of hyperkinetic disorder (F90 & F90.1). A single dose-protocol incorporated the time course effects of both immediate release MPH and extended-release MPH (Concerta XL, Equasym XL) to determine comparable peak efficacy periods post intake.

RESULTS

  A robust treatment response with objective measures reverting to the population mean was found in 37 participants (84%). Three participants (7%) demonstrated a partial response to MPH and four participants (9%) were determined as non-responders due to deteriorating activity measures together with no improvements in attention and impulse control measures.

CONCLUSION

  Objective measures provide early into prescribing the opportunity to measure treatment response and monitor adverse reactions to stimulant medication. Most treatment responders demonstrated an effective response to MPH on a moderate testdose facilitating a swift and more optimal titration process.

Executive impairment determines ADHD medication response: implications for academic achievement

Methylphenidate (MPH) often ameliorates attention-deficit/hyperactivity disorder (ADHD) behavioral dysfunction according to indirect informant reports and rating scales. The standard of care behavioral MPH titration approach seldom includes direct neuropsychological or academic assessment data to determine treatment efficacy. Documenting "cool" executive-working memory (EWM) and "hot" self-regulation (SR) neuropsychological impairments could aid in differential diagnosis of ADHD subtypes and determining cognitive and academic MPH response. In this study, children aged 6 to 16 with ADHD inattentive type (IT; n = 19) and combined type (n = 33)/hyperactive-impulsive type (n = 4) (CT) participated in double-blind placebo-controlled MPH trials with baseline and randomized placebo, low MPH dose, and high MPH dose conditions. EWM/ SR measures and behavior ratings/classroom observations were rank ordered separately across conditions, with nonparametric randomization tests conducted to determine individual MPH response. Participants were subsequently grouped according to their level of cool EWM and hot SR circuit dysfunction. Robust cognitive and behavioral MPH response was achieved for children with significant baseline EWM/SR impairment, yet response was poor for those with adequate EWM/ SR baseline performance. Even for strong MPH responders, the best dose for neuropsychological functioning was typically lower than the best dose for behavior. Findings offer one possible explanation for why long-term academic MPH treatment gains in ADHD have not been realized. Implications for academic achievement and medication titration practices for children with behaviorally diagnosed ADHD will be discussed.

Measurement of problem behaviour during medication evaluations

BACKGROUND

The focus of this review is on methods that are currently being used to evaluate the behavioural effects of medication for individuals with intellectual disabilities. First we describe what has been identified as the ideal criteria for conducting clinical trials and how these criteria may be adapted to do less controlled evaluations. The central theme is a review of the biological measures (e.g. labs, drug levels), behavioural rating scales and direct observation measures that are often used to evaluate medication effects. Issues related to how the side effects of medication can affect behaviour will also be discussed.

CONCLUSION

The importance of encouraging communication and collaboration across all systems of care and the use of socially valid measures are discussed.

Long-term changes in management following n-of-1 trials of stimulants in attention-deficit/hyperactivity disorder

OBJECTIVE

Our objective was to evaluate the long-term impact of n-of-1 trials-within-patient randomised, double-blind, cross-over comparisons of stimulant versus placebo or stimulant-on ADHD management.

METHODS

Telephone surveys at 3, 6 and 12 months. Main outcome measures included (1) changes in treatment before and after the n-of-1 trial, (2) congruence of management at follow-up with trial result, (3) reasons for any non-congruence, and (4) persistence of the joint patient-doctor decision over 12 months. Patients were children with clinically diagnosed ADHD, aged 5-16 years.

RESULTS

A total of 76 patients were followed up; 12 months' data were available for 67 (88%). Management changed from baseline for 46, 48 and 51% at 3, 6 and 12 months respectively. Most responders, 21/37 (57%), remained on the same stimulant at 12 months, compared to 9/24 (37%) non-responders. Of the remaining non-responders, 15/24 (62%) either switched (2/24, 8%) or ceased stimulants (13/24, 54%). The rate of congruence with the test result was 45/65 (69%) at 3 months, 44/67 (66%) at 6 months and 40/67 (60%) at 12 months. Persistence with the post-trial decision over 12 months was high (79-85%) whether the decision was to continue or to cease stimulants.

CONCLUSIONS

Although not conclusive because there was no control group, our results suggest that n-of-1 trials may improve rational treatment of ADHD.

An n-of-1 trial service in clinical practice: testing the effectiveness of stimulants for attention-deficit/hyperactivity disorder

OBJECTIVE

We sought to describe the clinical use of n-of-1 trials for attention-deficit/hyperactivity disorder in publicly and privately funded family and specialized pediatric practice in Australia.

METHODS

We used a within-patient randomized, double-blind, crossover comparison of stimulant (dexamphetamine or methylphenidate) versus placebo or alternative stimulant using 3 pairs of treatment periods. Trials were conducted from a central location using mail and telephone communication, with local supervision by the patients' clinicians.

PATIENTS

Our study population included children with clinically diagnosed attention-deficit/hyperactivity disorder who were aged 5 to 16 years and previously stabilized on an optimal dose of stimulant. They were selected because treatment effectiveness was uncertain.

MAIN OUTCOME MEASURES

Our measures included number of patients recruited, number of doctors who used the service, geographic spread, completion rates, response rate, and post-n-of-1 trial decisions.

RESULTS

Forty-five doctors across Australia requested 108 n-of-1 trials, of which 86 were completed. In 69 drug-versus-placebo comparisons, 29 children responded better to stimulant than placebo. Immediately posttrial, 19 of 25 drug-versus-placebo responders stayed on the same stimulant, and 13 of 24 nonresponders ceased or switched stimulants. In 40 of 63 for which data were available, posttrial management was consistent with the trial results. For all types of n-of-1 trials, management changed for 28 of 64 children for whom information was available.

DISCUSSION

Attention-deficit/hyperactivity disorder n-of-1 trials can be implemented successfully by mail and telephone communication. This type of trial can be valuable in clarifying treatment effect when it is uncertain, and in this series, they had a noticeable impact on short-term management.