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23 Apr 2018

Hollis C et al. J Child Psychol Psychiatry 2018; 59: 1298-1308

The current ‘gold-standard’ process for diagnosing ADHD relies on clinical interviews and reports from multiple informants. This is a time-consuming process, and any inconsistencies can lead to delays and uncertainty in diagnosis. Early diagnosis and treatment of ADHD reduces the risk of adverse long-term outcomes, therefore swift and confident diagnosis or exclusion is needed. The US Food and Drug Administration has approved the QbTest* as a decision-aid tool to be used alongside standard clinical assessment of ADHD.

The AQUA-Trial (Assessing QbTest Utility in ADHD-Trial) was a two-arm, parallel-group, single-blind, multicentre diagnostic randomised controlled trial conducted across 10 child and adolescent mental health services and community paediatric sites in England. All participants (aged 6–17 years) received a QbTest at one of their first three clinical appointments, and were randomly assigned to either the results of the QbTest being reported to their clinician immediately, or having their results withheld until the end of the study (n=123 and n=127, respectively). The aim of this study was to determine the effects of the QbTest on the number of consultations required to reach diagnosis or exclusion of ADHD, as well as the number of days taken and the duration of consultations (recorded in minutes) to reach the same diagnostic decision. Additionally, the effects of the QbTest on diagnostic accuracy, clinicians’ confidence in diagnosis and health economics were also investigated.

The study results showed that:

  • Clinicians who had access to their patient’s QbTest report were significantly more likely to reach a diagnostic decision regarding ADHD faster compared with those whose patient’s QbTest results were withheld (hazard ratio 1.44; 95% confidence interval [CI] 1.04–2.01; p=0.029); the number of consultations until a diagnostic decision was made was the primary outcome of this study.
  • At 6 months, clinicians with access to the QbTest report were able to make a diagnostic decision (i.e. ADHD or no ADHD) for 76% of participants compared with only 60% when the QbTest report was withheld (odds ratio [OR] 2.43; 95% CI 1.35–4.49; p=0.003).
  • An exploratory analysis showed that clinicians who had access to the QbTest were twice as likely to rule out a diagnosis of ADHD in participants (20% vs 9%; relative risk reduction 2.14; 95% CI 1.00–4.59; p=0.049) and were more confident in their diagnostic decisions about ADHD (OR 1.77; 95% CI 1.09–2.89; p=0.022) compared with those who did not.
  • Total consultation time was significantly reduced by 15% when a QbTest report was immediately available to clinicians (time ratio 0.85; 95% CI 0.77–0.93; p=0.001).
  • Diagnostic accuracy remained consistent across both arms (p=0.64).
  • Although health-economic analysis showed slight savings with the use of the QbTest, these were small, and an interpretation of ‘cost-neutral’ would be more appropriate.

Limitations of this study included the relatively short follow-up period of 6 months, which meant that almost one-third of participants had yet to receive a diagnostic decision at the end of the study period. Therefore, determining the effect of the QbTest on this group was not possible. In addition, the scale used for diagnostic confidence was created specifically for this study and as such has no established validity or reliability. Moreover, confidence in clinical diagnosis could potentially be influenced by the clinicians’ familiarity with the QbTest. Finally, assessments of diagnostic accuracy must be considered in light of the lack of a ‘gold-standard’ diagnostic measure.

The authors suggested that implementation of the QbTest as an adjunct to clinical diagnostic decision-making could improve the efficiency of diagnosis and reduce the length of time in which a clinical decision regarding ADHD can be made. Results from this study indicate that clinicians were more confident and comfortable with their diagnostic decisions, especially when excluding ADHD as a diagnosis. The authors do not recommend that the QbTest be used exclusively to diagnose ADHD, as it did not show increased accuracy compared with standard clinical assessments. However, qualitative data suggest that parents and clinicians demonstrate favourable support of the QbTest, and when coupled with the ‘cost-neutral’ economic assessment in this study, this suggests that incorporation of the QbTest in the UK may aid the development of ADHD care pathways.

Read more about the QbTest in ADHD diagnosis here


*The QbTest combines a computerised continuous performance test (CPT), an objective measure of attention, with an infra-red camera that tracks a reflector placed on the participant’s forehead, thereby providing an objective measure of motor activity during the CPT. This allows an objective standardised measurement of attention, impulsivity and activity, corresponding to the three symptom domains of ADHD. Two formats of the QbTest are available with selection based on age (QbTest for 7–12 years and QbTest+ for 12+ years). The QbTest is a simple target-detection (go/no-go) task, while the QbTest+ includes a working memory component

Hollis C, Hall CL, Guo B, et al. The impact of a computerised test of attention and activity (QbTest) on diagnostic decision‐making in children and young people with suspected attention deficit hyperactivity disorder: single‐blind randomised controlled trial. J Child Psychol Psychiatry 2018; 59: 1298-1308.

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