Abstract
Pill swallowing difficulty may occur as an isolated phenotype despite preserved food and liquid swallowing and may require different clinical pathways than general oropharyngeal dysphagia. We translated, culturally adapted, and validated the Turkish PILL-5 (PILL-5(TR)) and tested its ability to discriminate isolated pill swallowing difficulty from healthy adults and oropharyngeal dysphagia. We performed forward-back translation, expert committee review, and cognitive debriefing (n = 30). Adults (N = 348) were classified as healthy controls (n = 175), isolated pill swallowing difficulty (Functional Oral Intake Scale, FOIS = 7; n = 107), or oropharyngeal dysphagia (n = 66). We evaluated internal consistency, test-retest reliability (n = 48; 7-14 days), structural validity using exploratory factor analysis and common-factor-based parallel analysis, convergent validity with the Eating Assessment Tool-10 (EAT-10), the Swallowing Quality of Life questionnaire (SWAL-QOL), and the Dysphagia Handicap Index (DHI), and screening discrimination using receiver operating characteristic (ROC) analyses. PILL-5(TR) showed strong known-groups separation (means: 0.37, 5.81, and 10.47; p < 0.001), and the combined factor-analytic findings supported a predominantly unidimensional structure. Reliability was good (Cronbach's α = 0.865; intraclass correlation coefficient (ICC) = 0.869). In the clinical sample, PILL-5(TR) correlated strongly with EAT-10 (Spearman's ρ = 0.749), moderately with DHI (ρ = 0.387), and inversely with SWAL-QOL (ρ=-0.482) (all p < 0.001). In the study sample, discrimination between isolated cases and healthy controls was excellent (area under the ROC curve [AUC] = 0.992; preliminary threshold ≥ 2; sensitivity 1.00; specificity 0.87), while discrimination between oropharyngeal dysphagia and isolated cases was acceptable (AUC = 0.793; preliminary threshold ≥ 7; sensitivity 0.82; specificity 0.71). PILL-5(TR) is a valid and reliable pill-specific patient-reported measure. The preliminary thresholds may help inform pill-focused screening, triage, and medication-safety counselling in Turkish-speaking populations, but require external validation in more heterogeneous clinical samples.