A preliminary investigation of potential biases in phonation threshold pressure analysis

Phonation threshold pressure (PTP) is a voice measure used in both research and clinic. PTP data analysis is susceptible to bias from investigator awareness of experimental hypothesis, and poor investigator training. The objective of this study was to systematically examine the role of these two biases on PTP data analysis.

Prospective design.

Two trained investigators analyzed PTP datasets. The datasets were identical, but uniquely labeled so that the investigators were not aware that the datasets contained the same data. Each investigator analyzed two datasets. For one dataset, investigators were "blinded" to the experimental hypothesis. For the other dataset, the investigators were "unblinded" and provided a fake experimental hypothesis. Intraclass correlations were used to examine intrarater and interrater reliability.

For both investigators, intraclass correlations within the excellent range were obtained for intrarater reliability. In contrast, lower intraclass correlations were obtained for interrater reliability.

The high intrarater reliability obtained in this preliminary study suggests that awareness of experimental hypothesis may not significantly bias PTP analysis. Conversely, lower interrater reliability is indicative of differences between investigators analyzing the same data. Our findings contribute to the growing body of literature that seeks to standardize the use of PTP in research and the clinic. Future investigations are needed to identify methods to improve interrater reliability and that quantify the effects of biases on PTP data collection.