Association Between Salivary Substance P and Aspiration on Videofluoroscopic Swallow Study in Infants and Toddlers

To determine the association between salivary substance P (SP) concentration and aspiration on videofluoroscopic swallow study (VFSS) in children with oropharyngeal dysphagia.

We recruited children younger than 2 years of age who underwent VFSS within 3 months of study enrollment. Saliva samples were collected using absorbent collection devices and SP levels were measured by enzyme-linked immunosorbent immunoassays. We used the Student t test to compare levels between subjects with and without aspiration. Exploratory receiver operating characteristic analyses were used to determine optimal cut-off values and calculate sensitivity and specificity compared with gold-standard VFSS results. A subgroup analysis included only subjects with saliva collected within 1 month of VFSS.

The cohort included 50 subjects with age 8.16 ± 0.83 months at sample collection. SP concentrations were 344.7 ± 42.9 pg/mL for patients with aspiration compared with 105.7 ± 40.5 pg/mL for those without aspiration (P < .001). On receiver operating characteristic analysis, the area under the curve was 0.868 (95% CI 0.721-1.0, P < .001). A cutoff of 65 pg/mL provided 97% sensitivity (95% CI 86%-99%) and 75% specificity (95% CI 43%-95%) for predicting aspiration on VFSS. In a subgroup analysis with 29 subjects who had VFSS within 1 month of sample collection, the area under the curve was 0.964 (95% CI 0.98-1.0, P < .001). A cutoff of 63.2 pg/mL provided 100% sensitivity (95% CI 85%-100%) and 83.3% specificity (95% CI 36%-100%) for predicting aspiration on VFSS.

Salivary SP concentrations were found to be significantly greater in children with aspiration. Salivary SP may represent an early candidate biomarker that could be used to predict risk of aspiration in infants and toddlers.