Does Inclusion of Thickened Liquids in a Modified Barium Swallow Study (MBSS) Protocol Affect DIGEST Grades?

The Dynamic Imaging Grade of Swallowing Toxicity (DIGEST) is a psychometric tool used during modified barium swallow studies (MBSSs) to grade swallowing safety, efficiency, and overall pharyngeal swallow function ranging from 0 (no impairment) to 4 (life-threatening). DIGEST was originally validated on a protocol without routine inclusion of thickened liquids. To ensure stability of DIGEST in different settings, we aimed to assess whether DIGEST grades remained stable when derived from a bolus protocol with or without standard inclusion of thickened liquids. MBSSs from 118 unique participants were retrospectively analyzed by 4 reliable raters using a master protocol of thin, thickened, pudding, and solid boluses. DIGEST grades were derived from four bolus protocol conditions: (1) DIGEST core protocol (without thickened liquids); (2) core plus mildly thick liquid; (3) core plus moderately thick; and (4) core plus mildly and moderately thick. Prevalence and Bias-Adjusted Kappa (PABAK) values were calculated to determine agreement of DIGEST grades between the core protocol and variations. PABAK ranged from 0.83 to 1.00 (near-perfect to perfect agreement). In rare instances where thickened liquids affected grades, they invariably worsened by one grade. There was no clear change-driving bolus type for this effect. Safety was more susceptible to change than efficiency. Inclusion of thickened liquids does not appear necessary in a minimum bolus protocol for DIGEST. Clinicians and researchers who wish to routinely include thickened liquids in their protocol should be aware that DIGEST grades may be worsened by one in a minority of cases and that safety grades appear more likely to be affected than efficiency grades.