Reliability of Outcome Measures to Assess Consonant Proficiency Following Cleft Palate Speech Intervention: The Percentage of Consonants Correct Metric and the Probe Scoring System

Abstract

Purpose This study compared the inter- and intrarater reliability of the percentage of consonants correct (PCC) metrics and the probe scoring system between an experienced and a less experienced rater and between two experienced raters. In addition, these outcome measures' ability to reflect changes following speech intervention was measured. Method During Phase 1, two raters (Rater 1 with 5 years of experience in cleft-related speech disorders and Rater 2 with limited experience in cleft-related speech disorders) independently assessed 134 speech samples at the word and sentence levels, which were collected on different data points before, during, and following a cleft palate speech intervention. During Phase 2, a third rater (with 8 years of experience) analyzed 34 speech samples. The percentage of consonants correct–revised, the percentage of correct places and manners, and probe scores at the word and sentence levels were measured. Results Poor-to-moderate interreliability between Raters 1 and 2 was found due to differences in error classification. Interrater reliability between Raters 1 and 3 was very good for both the PCC metrics and the probe scores. The interrater reliability for the amount of targets elicited was lower compared to the interrater reliability for the amount of targets correct. The probe scoring system demonstrated a greater ability to detect changes toward the correct production of the target consonant compared to the PCC metrics. Conclusions Having an experience with the assessment of cleft-related speech disorders is a crucial factor to gain reliable results. The interrater reliability for the PCC metrics and the probe scoring system between two experienced raters did not differ, suggesting that both outcome measures can be used in cleft palate speech intervention studies. Despite the ability of the probe scoring system to detect changes, further research should provide insight in the benefits of this system both for research and clinical purposes.