Drooling rating scales in Parkinson's disease: A systematic review

Drooling is a clinically relevant non-motor symptom of people with Parkinson's disease (PwP). Several drooling rating scales are available. Nevertheless, the compelling scientific evidence supporting their validity is limited. This study aims to evaluate clinical rating scales for drooling, assessing their characteristics, clinimetric properties, and clinical utility classification.

A systematic review was undertaken. Two reviewers performed independent literature searches using the CENTRAL®, CINAHL®, Embase®, MEDLINE®, SciElo®, and SPEECH BITE® databases. We used consensus-based standards for the selection of health measurement instruments (COSMIN) and the International Parkinson's disease and the Movement Disorders (MDS) criteria to evaluate the included rating scales.

The following six rating scales were identified: Drooling Impact Scale (DIS), Sialorrhea Scoring Scale (SSS), Drooling Severity and Frequency Scale (DSFS), Drooling Rating Scale (DRS), Sialorrhea Clinical Scale for Parkinson Disease (SCS-PD), and the Radboud Oral Motor inventory for Parkinson's disease - Saliva (ROMP-saliva). The scales had heterogeneous characteristics: (i) not all were created/adapted for PwP; (ii) different dimensions associated with drooling are assessed; (iii) cross-cultural adaptations are limited to some languages. The clinimetric properties showed: (i) target population size limitations; (ii) incomplete reliability analysis; (iii) lack of robust validity; (iv) sensitivity to change not fully explored. Following the MDS criteria, only one tool was classified as "recommended", the ROMP-saliva.

This review provides information for an adequate selection of a drooling rating scale for clinical and/or research purposes. To date, ROMP-saliva is the only scale with substantial evidence of its clinimetric properties adequacy and data in PwP.