Bronchodilator response (BDR) assessment is routinely included in pulmonary evaluation before hematopoietic cell transplantation (HCT), but its prognostic significance remains uncertain. Recent European Respiratory Society/American Thoracic Society (ERS/ATS) criteria changes complicate interpretation.

To examine associations between BDR and clinical outcomes in HCT recipients and compare prognostic utility of traditional versus revised BDR criteria.

In this single-center study of 1,255 adult allogeneic HCT recipients (2005–2021), we assessed BDR using both 2005 criteria (≥12 % and ≥200 mL increase in FEV ₁ /FVC) and 2022 criteria ( > 10 % of predicted increase). Primary outcomes included bronchiolitis obliterans syndrome (BOS) development, 120-day ICU admission, and survival.

Among patients (58 % male, mean age 51.3 ± 13.6 years), positive BDR frequency was low (11.5 % by 2005 criteria, 14.2 % by 2022 criteria), with high concordance (> 94 %). BDR did not predict BOS development, with similar pre-transplant FEV ₁ responses between patients who later developed BOS and those who did not (5.0 % vs. 4.9 %, p = 0.841). Unadjusted analyses showed pre-transplant BDR positivity using 2005 criteria was associated with increased mortality (HR = 1.45, p = 0.006) and ICU admission (HR = 1.65, p = 0.005), but these associations did not persist after adjusting for baseline FEV ₁ (aHR = 1.17, p = 0.275; aHR = 1.09, p = 0.648).

BDR testing provides minimal additional prognostic information beyond baseline lung function assessment in HCT recipients and does not predict BOS development. Our findings support that BOS represents a fibroproliferative process distinct from disorders characterized by airway hyperresponsiveness, suggesting bronchodilator testing could be eliminated from standard HCT protocols without compromising risk assessment.