To the Editor: We applaud the efforts of Wasiak et al to apply the principles of evidence-based medicine to answer clinical questions.1 However, it is important to understand the historical context of clinical trials reported in the literature, and, when necessary (eg, when conducting a meta-analysis or when the results of trials appear to conflict), to seek additional information from the authors.

One of us (H K G) designed the randomised-controlled trial (RCT) reported by Corry et al.2 It was a pilot study and not a definitive clinical trial. The primary outcome measure was resonant frequency, an objective measure of muscle stiffness. This trial was conducted before the introduction of validated outcome measures for assessing upper limb function in children with cerebral palsy, and it was not possible to perform any sample size calculation for functional outcomes. At 12 weeks in the group receiving injections of botulinum toxin A, there was a significant difference in grasp and release but not in the ability to pick up coins. It is not surprising therefore that this study found significant decreases in muscle stiffness, but the functional results were inconclusive.

The other RCT identified by Wasiak et al also involved one of us (D F).3 It was designed specifically to investigate functional outcomes, a sample size calculation was performed from pilot work, and a specific functional outcome measure (QUEST) was used. This study reported significant functional improvements after the use of botulinum toxin combined with occupational therapy.

These two studies, when understood in their historical sequence, should therefore be considered complementary and not contradictory. It is important to assess the quality of randomised clinical trials as well as their conclusions (eg, using the Physiotherapy Evidence database PEDRO scale <http://ptwww.fhs.usyd.edu.au/pedro>).4,5 The smaller study by Corry et al2 had insufficient power and inadequate methodology to investigate functional outcomes. On the other hand, the conclusions of the study by Fehlings et al3 should be taken as the current level of evidence. We therefore submit that the conclusion drawn by Wasiak et al is incorrect. We support further research to evaluate and strengthen the evidence relating to botulinum toxin A and upper-extremity function.6