Apparent lack of practice effects in the Test of Variables of Attention (TOVA) in adult ADHD.

The test of variables of attention (TOVA) is a continuous performance test commonly used as an aid for diagnosis of ADHD and assessment of treatment response. It has been studied and standardized in both children and adults. As a repetitive measurement of treatment efficacy, used both in research and in the clinic, it's important to disprove a practice effect. A retrospective cohort analysis was done, using only the placebo-arm participants from two different randomized, multicenter, double-blind clinical trials on the efficacy of a non-stimulant (metadoxine-XR). In order to reveal the practice effects, only the participants that showed no placebo effect (< 25% improvement), in the Conners' Adult ADHD Rating Scale-investigator rated (CAARS-Inv), the gold standard, were included. Demographic data, CAARS-Inv baseline and TOVA results during each visit were recorded and analyzed. Ninety-one participants from two studies were pooled (2014 n = 24, 2016 n = 67). They did not differ significantly in any demographic parameter, most side effect frequencies, and CAARS-Inv baseline scores. The baseline TOVA performances demonstrated similarity in the degree of inattention, variability, impulsivity, and response time. The TOVA scores were not altered significantly between visits, as assessed by repeated-measures analysis of variance. No significant differences were detected between the TOVA baseline-to-endpoint scores as assessed by paired t test. No practice effects were detected, in both clinical trials, suggesting that the results of the TOVA are likely to represent genuine changes in attentional performance. Further studies are needed to replicate these findings.