Validity of telephone calls to assess percentage of syllables stuttered with adolescents in clinical research

Purpose: Karimi, O'Brian, Onslow, and Jones (2013) reported, for adults, no systematic differences between percentage of syllables stuttered (%SS) scores during a 12-hour day and 10-minute phone calls. The present study replicated that finding with adolescents, using valid methods for the age group. The present study also extended that initial report by determining whether the gender of the caller influenced %SS scores. Method: Participants were 17 adolescents with stuttering. Percentage of syllables stuttered scores were obtained from a 12-hour day of the adolescents' lives, and two 10-minute unscheduled phone calls made before and after that day. One phone call was from a male caller and the other from a female caller. Results: For adolescents, analysis of covariance (ANCOVA) and intraclass correlations (ICC) replicated the overall Karimi, O'Brian, Onslow, and Jones (2013) finding. No significant differences were found between the %SS scores of the three speech samples, and these %SS scores were found to be highly correlated. However, in contrast to the Karimi, O'Brian, Onslow, and Jones (2013) finding with adults, Bland-Altman plot results revealed a caveat to this finding when applied to individual adolescents. Additionally, there was no effect due to the gender of the caller. Conclusion: A 10-minute phone call can be used confidently to assess group mean %SS scores during stuttering research with adolescents. However, a 10-minute phone call cannot be used confidently to assess %SS scores of individual adolescent participants. For the latter context, such as with data-based case studies and single-subject experimentation, we recommend supplementing %SS scores with self-reported severity scores.