Applicability and reliability of the IDDSI functional diet scale (IDDSI-FDS) in clinical reports of patients with oropharyngeal dysphagia.

backgroundThe International Dysphagia Diet Standardization Initiative Functional Diet Scale (IDDSI-FDS) was developed to quantify functional oral intake within the IDDSI framework. Although promising, evidence supporting its use in routine clinical documentation remains limited. This study aimed to examine the applicability of the IDDSI-FDS when retrospectively applied to medical reports of patients with oropharyngeal dysphagia.

methodsMedical reports were randomly selected from 200 Fiberoptic Endoscopic Evaluation of Swallowing (FEES) examinations performed between January 2024 and September 2025 at a tertiary-care hospital. Three trained raters independently classified each report using IDDSI levels for solids and liquids, the Functional Oral Intake Scale (FOIS), and the corresponding IDDSI-FDS score. After two weeks, raters repeated the classifications under blinded, randomized conditions. Applicability was assessed through classifiable proportion and time required per classification.

resultsReliability was examined using weighted Cohen's kappa and Gwet's AC2 (inter- and intra-rater), while convergent validity was assessed via Spearman correlation between FOIS and IDDSI-FDS. Of the 71 initially selected reports, 67 (94.4%) were classifiable after excluding 4 due to incomplete dietary information, confirming high applicability of the scale to standard clinical documentation. Mean classification time was 64 ± 8 s per case. Inter-rater agreement was almost perfect for FOIS (κ range: 0.991-0.996, AC2: 0.991- 0.996) and perfect for IDDSI-FDS (κ = 1.00, AC2 = 1.00 for all comparisons). Intra-rater reliability was perfect across all raters and both scales (κ = 1.00; AC2 = 1.00). FOIS and IDDSI-FDS showed strong positive correlation in both assessment rounds (ρ = 0.850, p < .001), demonstrating excellent convergent validity. The IDDSI-FDS can be reliably derived from retrospective FEES documentation, with perfect intra-rater stability and near-perfect inter-rater agreement. Its strong correlation with FOIS supports the functional validity of the scale. These findings indicate that the IDDSI-FDS is a practical, standardizable, and clinically robust tool for documenting dietary recommendations in oropharyngeal dysphagia.