Application of Global Lung Function Initiative Global Spirometry Reference Equations across a Large, Multicenter Pulmonary Function Lab Population.

Rationale: Global Lung Function Initiative (GLI) Global spirometry reference equations were recently derived to offer a "race-neutral" interpretation option. The impact of transitioning from the race-specific GLI-2012 to the GLI Global reference equations is unknown. Objectives: Describe the direction and magnitude of changes in predicted lung function measurements in a population of diverse race and ethnicity using GLI Global in place of GLI-2012 reference equations. Methods: In this multicenter cross-sectional study using a large pulmonary function laboratory database, 109,447 spirometry tests were reanalyzed using GLI Global reference equations and compared with the existing GLI-2012 standard, stratified by self-reported race and ethnicity. Measurements and Main Results: Mean FEV1 and FVC percent predicted increased in the White and Northeast Asian groups and decreased in the Black, Southeast Asian, and mixed/other race groups. The prevalence of obstruction increased by 9.7% in the White group, and prevalences of possible restriction increased by 51.1% and 37.1% in the Black and Southeast Asian groups, respectively. Using GLI Global in a population with equal representation of all five race and ethnicity groups altered the interpretation category for 10.2% of spirometry tests. Subjects who self-identified as Black were the only group with a relative increase in the frequency of abnormal spirometry test results (32.9%). Conclusions: The use of GLI Global reference equations will significantly impact spirometry interpretation. Although GLI Global offers an innovative approach to transition from race-specific reference equations, it is important to recognize the continued need to place these data within an appropriate clinical context.

Isolated Elevation in Lung Residual Volume Is Associated With Airway Diseases.

BACKGROUND: Residual volume (RV) is a derived lung compartment that correlates with air trapping in the context of air flow obstruction on spirometry. The significance of an isolated elevation in RV in the absence of other pulmonary function test (PFT) abnormalities is not well defined. We sought to assess the clinical and radiologic findings associated with isolated elevation in RV. METHODS: We searched our out-patient PFT database at Mayo Clinic (Rochester, Minnesota) from 2016-2018 for adult patients with isolated elevation in RV. We defined isolated elevation in RV as RV ≥ upper limit of normal or ≥ 130% predicted with normal total lung capacity (TLC), spirometry, and diffusion capacity of the lung for carbon monoxide (DLCO). We then matched this high-RV group by age and sex to an equal number of individuals with normal RV, TLC, spirometry, and DLCO (normal-RV group). RESULTS: We identified 169 subjects with isolated elevation in RV on PFTs, with a median age of 73 y; 55.6% were female, and median body mass index was 26.8 (vs 29.8 in the normal-RV group). The median RV was 3.08 L (134% predicted, interquartile range [IQR] 130-141) in the high-RV group and 2.26 L (99% predicted, IQR 90-109) in the normal-RV group (P < .001). Subjects with high RV were more likely to have smoked (54% vs 40%, P = .01) and almost twice as likely to have a maximum voluntary ventilation < 30 times the FEV1 (21% vs 12%, P = .02). Clinically, asthma (21% vs 11%, P = .01) and non-tuberculous mycobacterial lung infections (12% vs 2%, P = .001) were more prevalent in the high-RV group. On chest computed tomography, bronchiectasis (31% vs 15%, P = .008), bronchial thickening or mucus plugging (46% vs 22%, P < .001), and emphysema (13% vs 5%, P = .046) were more common in the high-RV group. CONCLUSIONS: Isolated elevation in RV on PFTs is a clinically relevant abnormality associated with airway-centered diseases.