Reflections on Clinical and Statistical Use of the Penetration-Aspiration Scale

Abstract

The 8-point Penetration-Aspiration Scale (PAS) was introduced to the field of dysphagia in 1996 and has become the standard method used by both clinicians and researchers to describe and measure the severity of airway invasion during swallowing. In this article, we review the properties of the scale and explore what has been learned over 20 years of use regarding the construct validity, ordinality, intervality, score distribution, and sensitivity of the PAS to change. We propose that a categorical revision of the PAS into four levels of increasing physiological severity would be appropriate. The article concludes with a discussion of common errors made in the statistical analysis of the PAS, proposing that frequency distributions and ordinal logistic regression approaches are most appropriate given the properties of the scale. A hypothetical dataset is included to illustrate both the problems and strengths of different statistical approaches.

Impact of carbonation on neurogenic dysphagia and an exploration of the clinical predictors of a response to carbonation

“…). Alternative methods for the interpretation of PAS ordinal data have been the subject of a recent discussion paper (Steele and Grace‐Martin ) with regard to optimal statistical analysis including the merits of collapsing the scale into categorical levels of airway compromise. The manner in which PAS scores were grouped in this study may benefit from revision in future, but was based on provision of clinically salient information for dysphagia risk management.…”

“…The potential for differences in PAS ratings between the recruiting clinician who judged PAS scores online in the VFSS suite (with increased frames per second available for viewing) versus ratings made using the videos observed via the DSW (with reduced frames per second available for viewing) is also acknowledged (Burns et al 2015). Alternative methods for the interpretation of PAS ordinal data have been the subject of a recent discussion paper (Steele and Grace-Martin 2017) with regard to optimal statistical analysis including the merits of collapsing the scale into categorical levels of airway compromise. The manner in which PAS scores were grouped in this study may benefit from revision in future, but was based on provision of clinically salient information for dysphagia risk management.…”

Cough response to aspiration in thin and thick fluids during FEES in hospitalized inpatients

“…The ordinality of the PAS remains questionable. In clinical practice, a PAS score of 5 is often considered more severe than a score of 6, which has driven suggestions for alternative interpretation models (Steele and Grace‐Martin ). One significant limitation of using the PAS in this study is that, in combining several rating dimensions in a single multi‐item scale, the scale fails to capture responsiveness to airway invasion consistently.…”

Prediction of aspiration in dysphagia using logistic regression: oral intake and self-evaluation

“…Recordings were rated by consensus among two SLPs using the Penetration Aspiration Scale (PAS) [27]. FEES results were dichotomised into no aspiration (PAS score 1-5) or aspiration (PAS scores 6-8) [28]. If the patient aspirated during any of the (maximum of) nine trials with any of the three consistencies, he or she was considered an aspirating patient in this study.…”