The original derivation study included 88,074 adults (age >40 years) admitted to US hospitals with acute exacerbation of COPD between 2004 and 2006, using age, blood urea nitrogen, mental status and pulse rate to predict in-hospital mortality and need for mechanical ventilation. Overall in-hospital mortality was about 2%.
The score was internally validated within the same database, with AUROC around 0.71 for mortality and 0.77 for need for mechanical ventilation. Mortality rose from about 0.3% in class I (score 0, age ≤65 years, no BAP factors) to about 14% in class V (score 4, all three BAP factors present).
In an external US cohort of 34,699 AECOPD admissions, mortality again increased from <1% in class I to >25% in class V, and the need for mechanical ventilation from about 2% to 55%; AUROC for the composite outcome of death or mechanical ventilation was about 0.79.
A multicentre Italian emergency department cohort of 2,908 presentations reported only modest discrimination (AUROC 0.64 for in-hospital death or invasive mechanical ventilation), and the authors did not support using BAP-65 alone to guide ED disposition.
Indian COPD guidelines include BAP-65 (elevated BUN, altered mental status, pulse >109/min, age >65 years) as one tool, alongside clinical severity assessment, to help identify exacerbation admissions that may require ICU-level care.
The score does not include arterial blood gases, chronic comorbidities, frailty, prior exacerbation history or treatment limitations; interpret results alongside these factors and local COPD or ICU pathways.

BAP-65 Score for Acute Exacerbation of COPD