UNLABELLED: The purpose of this study to compare the effectiveness of the Bronchiolitis Severity Score (BSS) and the Respiratory Distress Assessment Instrument (RDAI) in determining bronchiolitis severity and predicting outcomes. Additionally, it aimed to establish optimum cutoff points for both scores. In this prospective observational study, clinical details of enrolled infants, along with assessments using both scoring tools, were recorded. The performance of these scores in predicting "severe disease," defined by respiratory support requirements other than nasal prongs, PICU admission, respiratory acidosis, and/or altered consciousness, was evaluated. A total of 64 infants diagnosed with bronchiolitis were enrolled with a median age of 5 (3.8) months, and 16 (25%) infants had severe disease. BSS showed 25% sensitivity and 97.9% specificity at established cutoffs of >
8 for severe bronchiolitis. BSS performed better than RDAI in differentiating severe bronchiolitis [AUC, 0.733 vs 0.605
p = 0.035]. New cutoffs of >
5 points for BSS and >
8 points for RDAI increased BSS sensitivity to 68.8% and RDAI sensitivity to 56.3%. CONCLUSION: BSS demonstrated superior discriminative ability compared to RDAI in identifying severe bronchiolitis. New cutoff points enhanced BSS's ability to classify severe cases while establishing a cutoff for RDAI. Additional studies are required to validate these revised cutoffs. WHAT IS KNOWN: • Bronchiolitis severity score (BSS) and Respiratory Distress Assessment Instrument (RDAI) helps in determining bronchiolitis severity. WHAT IS NEW: • BSS has superior discriminatory ability as compared to RDAI in determining bronchiolitis severity. • This study also highlights that neither BSS nor RDAI is perfect, emphasizing the importance of clinical judgment over scoring systems.