External validation of the predictive swallow score for dysphagia in stroke patients

Post-stroke dysphagia (PSD) is a common complication following acute ischemic stroke (AIS). Predicting the recovery of swallow function remains challenging. The Predictive Swallow Score (PRESS) model, derived and validated in a Swiss cohort, sought to predict the recovery of PSD after AIS. We aimed to validate the PRESS model in a US-cohort, conducting a two-center retrospective review of 149 patients with AIS and functional oral intake scale (FOIS) ≤ 4.

We collected the predictors of recovery of PSD according to PRESS (age, NIH Stroke Scale (NIHSS), any2 score, stroke location, FOIS score), with a primary outcome of impaired swallow at day 7 (FOIS ≤ 4). Model validation was completed using the Hosmer-Lemeshow (HL) test, calibration plots, and AUC analysis.

Median (IQR) age was 74 (61-86); 53% were female. Median (Q1-Q3) NIHSS at presentation was 14 (7-20). HL test demonstrated that the PRESS model did not fit the validation data (p < 0.00001, x²=48.343, df=5), and the calibration curve analysis (intercept = -0.80 (95% CI: -1.21 to -0.38), slope = 0.60 (95% CI: 0.37 to 0.82)) also demonstrated a poor calibration of the model. Area under the curve analyses demonstrated a C statistic of 0.75 (95% CI 0.67-0.82), indicating suboptimal model discrimination in predicting the recovery of swallow 7 days following AIS. In particular, the model overpredicted dysphagia severity at day-7 in patients with higher PRESS scores and more severe strokes.

Further validation of the PRESS score in prospective cohorts is warranted. The suboptimal model performance could be attributed to temporal advances in stroke care, as the original PRESS cohort was derived between 2011 and 2014. Geographic variability in acute stroke care practice could also be a factor, as the PRESS score was derived solely from a European cohort. This study, however, is limited by its retrospective design and a lack of generalizability.