Kanj, A N

Abstract Background Single breath diffusing capacity of the lung for carbon monoxide (DLCO) remains the most widely used test to assess pulmonary gas exchange. GLI DLCO reference equations are based on a larger, more diverse dataset and offer age-specific and internally consistent reference values. However, their impact on interpretation in a real-world population remains uncertain. Research Question Describe the direction and magnitude of DLCO interpretation changes resulting from our multicenter PFT laboratory transition from Miller to GLI reference equations. Study Design and Methods In this multicenter cross-sectional study, we reanalyzed 88,060 DLCO measurements in a large pulmonary function laboratory database performed between 2016 and 2022 using GLI and Miller reference equations, stratified by self-reported race and ethnicity. Baseline patient characteristics and lung function measurements were summarized with continuous characteristics as median (IQR) and categorical variables as n (%). Kruskal-Wallis test was used to evaluate the difference between GLI and Miller DLCO % predicted difference between races, and two-by-two and four-by-four tables were generated to summarize the proportion of concordance and discordance of GLI to Miller severity levels. A repeated measures multivariable logistic regression was used to evaluate discordance between GLI and Miller severity and patient characteristics (age, sex, race, and BMI). Results We included 63,357 individuals with 88,060 PFT visits; 91.6% (58,076) identified as Caucasian, 5.2% (3,262) as Black, 1.4 % (895) as Asian, and 1.8% (1,113) as mixed/other race. Fifty-one percent were female with an median age of 64 years (range: 5- 85). 7.4% (6509) of DLCO results were discordant, with 0.5% (n = 439) abnormal by GLI only, and 6.9% (n = 6070) abnormal by Miller only. Compared to the Miller, GLI interpretations were associated with a greater shift toward normal interpretations. Younger age, lower BMI, female sex, and being of NE Asian, SE Asian, or Other/mixed race compared to Caucasian were associated with higher odds of discordance in DLCO severity/normal classification. Interpretation The use of GLI reference equations substantially alters the interpretation of DLCO results, shifting a meaningful subset of patients from abnormal to normal classification. While GLI reference equations offer more comprehensive, population-based approach, it is crucial to place these interpretations within the context of the patient presentation until further investigations more clearly define the clinical implications of these transitions. This abstract is funded by: none

Abstract Rationale Gastroesophageal reflux disease (GERD) is a common comorbidity in non-cystic fibrosis bronchiectasis (NCFB), yet its impact on clinical outcomes remains poorly defined. We sought to determine whether GERD is associated with worse clinical outcomes in patients with NCFB using a large, real-world database. Methods We conducted a retrospective cohort study using the TriNetX platform, identifying patients with NCFB (ICD-10 J47*) with and without concurrent GERD (ICD-10 K21*), excluding those with cystic fibrosis (ICD-10 E84*). Propensity score matching (PSM) was performed using 1:1 nearest neighbor matching without replacement, controlling for age, sex, race/ethnicity, obesity, socioeconomic risk factors, and tobacco use. Primary outcomes included pneumonia, bronchiectasis exacerbations, intensive care unit admission, mechanical ventilation, and mortality. Statistical analyses included risk ratios and Cox proportional hazards modeling for survival outcomes. Results Out of 421,710 patients with NCFB in the dataset from January 2000 to September 2025, 186,874 (44%) had a diagnosis of GERD. After propensity score matching, 179,753 patients with NCFB+GERD and 179,753 patients with NCFB-only were included (mean age 74.0±13.1 years, 58.8% female, 67.1% White). Baseline characteristics were well-balanced after matching. Median follow-up was approximately 2.5 years for both cohorts (898 vs 889 days; similar means and IQR), ensuring balanced observation time. Compared to NCFB-only, NCFB+GERD was associated with increased risks for mortality (risk ratio 1.04, 95% CI 1.02-1.05; p < 0.001), pneumonia (risk ratio 1.06, 95% CI 1.05-1.08; p < 0.001), bronchiectasis exacerbations (risk ratio 1.03, 95% CI 1.01-1.06; p = 0.006), and mechanical ventilation (risk ratio 1.14, 95% CI 1.10-1.18; p < 0.001). Intensive care unit admission rates were comparable between groups (risk ratio 1.00; p = 0.65). Conclusions In this large propensity score-matched analysis, concurrent GERD in NCFB is independently associated with increased mortality, pneumonia, bronchiectasis exacerbations, and mechanical ventilation requirements. These findings suggest GERD may represent a modifiable risk factor warranting aggressive management in NCFB patients. Study limitations include retrospective design, reliance on ICD-10 coding accuracy, and potential unmeasured confounders. Our results support systematic screening and treatment of GERD in NCFB, but whether targeted GERD management can modify the natural history of NCFB future investigation. This abstract is funded by: None

Abstract Background Sputum color is a visual marker of airway inflammation and disease activity in bronchiectasis, ranging from clear or light gray (mucoid) to yellow-green (purulent), the latter largely reflecting neutrophil myeloperoxidase release. This study evaluated associations between sputum color and common clinical markers of disease activity to determine which parameters differed most between color categories. Methods Forty spontaneous sputum samples were analyzed from 80 consecutive adults with non-cystic fibrosis bronchiectasis (median age 70 years [IQR 12]; 74% female) enrolled between January 2024 and April 2025 in an observational study. Sputum color was graded using the Murray Sputum Color Chart and classified as mucoid (color #1) or purulent (colors #2-4). Clinical parameters, including blood cell counts, C-reactive protein (CRP), fractional exhaled nitric oxide (FeNO), and results of bacterial and acid-fast bacillus cultures (induced or bronchoscopic), were obtained from medical records if available within one month of enrollment. Categorical variables were analyzed using chi-square or Fisher’s exact tests and continuous variables with the Mann-Whitney U test. A secondary analysis compared patients who could versus could not produce spontaneous sputum. Results Of 40 samples, 20 (50%) were purulent. Blood neutrophil counts (median 4.5 vs. 3.9 x109/L), neutrophil-to-lymphocyte ratios (2.5 vs. 2.6), and eosinophil counts (1.7 vs. 1.7 x109/L) did not differ significantly between groups (n = 26). FeNO was normal in all 10 patients with available data and was not analyzed further. CRP was higher among patients with purulent sputum (4.6 vs. <3 mg/L; n = 20; p = 0.044). Bacterial growth was more frequent in purulent than mucoid samples (73% vs. 31%; n = 31; p = 0.032). Isolates in the purulent group included Klebsiella, Pseudomonas, Staphylococcus, and Streptococcus (n = 2 each), and single isolates of Acetobacter, Acinetobacter, Chryseobacterium, Delftia, Enterobacter, Escherichia, and Moraxella. In the mucoid group, Pseudomonas, Staphylococcus (n = 2 each), and Stenotrophomonas (n = 1) were identified. Mycobacterial growth did not differ significantly (20% vs. 12.5%; n = 31; p = 0.65). Patients unable to produce spontaneous sputum had a higher rate of mycobacterial isolation on induced/bronchoscopic samples (43% vs. 16%; n = 54; p = 0.027), though other parameters were similar. Over 90% of measurements were obtained within three days of enrollment, and freezing did not appear to alter sputum color. Conclusions Even within a small cohort, purulent sputum was associated with higher CRP and greater bacterial growth, supporting sputum color as a rapid, inexpensive marker of disease activity in bronchiectasis. Further research should clarify whether sputum color primarily reflects bacterial colonization, airway inflammation, or both. This abstract is funded by: None