Purpose: This report investigates whether parent-reported stuttering severity ratings (SRs) provide similar estimates of effect size as percentage of syllables stuttered (%SS) for randomized trials of early stuttering treatment with preschool children.
Method: Data sets from 3 randomized controlled trials of an early stuttering intervention were selected for analyses. Analyses included median changes and 95% confidence intervals per treatment group, Bland–Altman plots, analysis of covariance, and Spearman rho correlations.
Results: Both SRs and %SS showed large effect sizes from pretreatment to follow-up, although correlations between the 2 measures were moderate at best. Absolute agreement between the 2 measures improved as percentage reduction of stuttering frequency and severity increased, probably due to innate measurement limitations for participants with low baseline severity. Analysis of covariance for the 3 trials showed consistent results.
Conclusion: There is no statistical reason to favor %SS over parent-reported stuttering SRs as primary outcomes for clinical trials of early stuttering treatment. However, there are logistical reasons to favor parent-reported stuttering SRs. We conclude that parent-reported rating of the child’s typical stuttering severity for the week or month prior to each assessment is a justifiable alternative to %SS as a primary outcome measure in clinical trials of early stuttering treatment.

dx.doi.org/10.1044/2017_JSLHR-S-16-0448, hdl.handle.net/1765/105900
Journal of Speech, Language, and Hearing Research
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Erasmus MC: University Medical Center Rotterdam

Onslow, M. (Mark), Jones, M. (Mark), O’Brian, S. (Sue), Packman, A. (Ann), Menzies, R. (Ross), Lowe, R. (Robyn), … Franken, M.-C. (2018). Comparison of percentage of syllables stuttered with parent-reported severity ratings as a primary outcome measure in clinical trials of early stuttering treatment. Journal of Speech, Language, and Hearing Research, 61(4), 811–819. doi:10.1044/2017_JSLHR-S-16-0448