Validation of the Swedish Watson Dysphagia Scale for adult patients with eosinophilic esophagitis

Background: The Swedish Watson Dysphagia Scale (S-WDS) has been used to assess dysphagia in patients with eosinophilic esophagitis (EoE) but has not been validated for this patient group. The aim of this study was to validate the S-WDS for adult patients with EoE. Methods: Ninety-seven Swedish adult patients with EoE and 97 controls without dysphagia filled out the S-WDS, the Swedish Eosinophilic Esophagitis Activity Index (S-EEsAI) and a set of supplementary questions. The reliability of the S-WDS was evaluated using Cronbach's alpha, Pearson correlation of items and total score, and test-retest analysis (n = 29). Validity was investigated using Spearman correlations of the S-WDS items, S-EEsAI domains and a self-assessment score, and by investigating floor and ceiling effects. Results: The Cronbach's alpha of the S-WDS was 0.77 and all items demonstrated moderate to strong correlation to the S-WDS score (r = 0.40-0.81) indicative of sufficient reliability of the instrument. In addition, the test-retest results reflected excellent reliability with an intraclass correlation coefficient of 0.85 for the S-WDS score. Adequate validity of the instrument was demonstrated, the S-WDS score correlated moderately with the self-assessment score and with 4/6 S-EEsAI domains, and strongly with the remaining two domains. Floor effects were more common for liquids and soft-textured foods and ceiling effects increased with increasing food consistency. The S-WDS scores of the patient group were significantly different from those of the nondysphagia control group (P < 0.001). Conclusion: The S-WDS instrument is an appropriate and valid instrument for assessment of dysphagia in patients with EoE.