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The following is a summary of “Single breath nitrogen test as predictor of lung function decline and COPD over an 8-year follow-up,” published in the November 2024 issue of Pulmonology by Pistelli et al. 

The single breath nitrogen (SBN₂) test, proposed in the 70s for early detection of small airway disease, has been infrequently studied in longitudinal settings to evaluate its relationship with lung function decline or Chronic Obstructive Pulmonary Disease (COPD) incidence.  

Researchers conducted a retrospective study to evaluate whether SBN₂ test abnormalities were predictors of lung function decline and COPD incidence over an 8-year follow-up.  

They included 907 adults (20+ years old; 56% males) from the Po River Delta epidemiological study who underwent the SBN₂ test at baseline and spirometry testing at both baseline and 8-year follow-up. The Multinomial and multiple regression models were used to evaluate the associations between SBN₂ indexes and rates of FEV₁ decline or COPD incidence over time, adjusting for sex, baseline age, height, FEV₁, and smoking status, and COPD was defined according to either GOLD or ATS-ERS criteria.  

The results showed that among the SBN₂ indexes, only the slope of the alveolar plateau (N₂ -slope) was significantly linked to FEV₁ decline rates (7.93 mL/year for each 1-unit change in N₂ -slope, P <0.0001) and an increased risk of developing COPD. The risk of COPD, as defined by GOLD, was higher in individuals with mild obstruction (RR 1.81, 95% CI 1.29-2.52) and moderate or severe obstruction (RR 2.78, 95% CI 1.70-4.53). According to ATS-ERS criteria, the risk for mild obstruction was (RR 1.62, 95% CI 1.14-2.29), and for moderate or severe obstruction (RR 3.40, 95% CI 1.72-6.73).  

Investigators concluded the N₂ -slope from the SBN₂ test emerged as a substantial predictor of lung function decline and COPD incidence over an 8-year follow-up, supporting the role of small airway disease in COPD progression. 

Source: sciencedirect.com/science/article/pii/S2531043722002124