Race-specific spirometry equations may overestimate asthma control in Black children and adolescents.

BACKGROUND: A growing body of evidence suggests that use of race terms in spirometry reference equations underestimates disease burden in Black populations, which may lead to disparities in pulmonary disease outcomes. Data on asthma-specific health consequences of using race-adjusted spirometry are lacking. METHODS: We performed a secondary analysis of 163 children from two observational asthma studies to determine the frequencies of participants with ppFEV1 < 80% (consistent with uncontrolled asthma) or ppFEV1 ≥ 80% using race-specific (GLI-African American or Caucasian) vs. race-neutral (GLI-Global) spirometry and their alignment with indicators of asthma control (Asthma Control Test™, ACT). Comparisons of mean ppFEV1 values were conducted using Wilcoxon matched-pairs signed-rank tests. Two group comparisons were conducted using Wilcoxon rank-sum tests. RESULTS: Data from 163 children (100 Black, 63 White) were analyzed. Mean ppFEV1 was 95.4% (SD 15.8) using race-specific spirometry and 90.4% (16.3) using race-neutral spirometry (p < 0.0001). Among 54 Black children with uncontrolled asthma (ACT ≤ 19), 20% had ppFEV1 < 80% using race-specific spirometry compared to 40% using race-neutral spirometry. In Black children with controlled asthma (ACT > 19), 87% had ppFEV1 ≥ 80% using race-specific compared to 67% using race-neutral spirometry. Children whose ppFEV1 changed to ≤ 80% with race-neutral spirometry had lower FEV1/FVC compared to those whose ppFEV1 remained ≥ 80% [0.83 (0.07) vs. 0.77 (0.05), respectively; p = 0.04], suggesting greater airway obstruction. Minimal changes in alignment of ppFEV1 with ACT score were observed for White children. CONCLUSIONS: Use of race-specific reference equations in Black children may increase the risk of inappropriately labeling asthma as controlled.

Impact of Spirometry Race-Correction on Preadolescent Black and White Children.

BACKGROUND: Race-correction for Black patients is standard practice in spirometry testing. History suggests that these corrections are at least partially a result of racist assumptions regarding lung anatomy among Black individuals, which can potentially lead to less frequent diagnoses of pulmonary diseases in this population. OBJECTIVE: To evaluate the impact of race-correction in spirometry testing among Black and White preadolescents, and examine the frequency of current asthma symptoms in Black children who were differentially classified depending on whether race-corrected or race-uncorrected reference equations were deployed. METHODS: Data from Black and White children who completed a clinical examination at age 10 years from a Detroit-based unselected birth cohort were analyzed. Global Lung Initiative 2012 reference equations were applied to spirometry data using both race-corrected and race-uncorrected (ie, population-average) equations. Abnormal results were defined as values less than the fifth percentile. Asthma symptoms were assessed concurrently using the International Study of Asthma and Allergies in Childhood questionnaire, while asthma control was assessed using the Asthma Control Test. RESULTS: The impact of race-correction on forced expiratory volume in 1 second (FEV1)/forced vital capacity ratio was minimal, but abnormal classification of FEV1 results more than doubled among Black children when race-uncorrected equations were used (7% vs 18.1%) and were almost 8 times greater based on forced vital capacity classification (1.5% vs 11.4%). More than half of Black children differentially classified on FEV1 (whose FEV1 was classified as normal with race-corrected equations but abnormal with race-uncorrected equations) experienced asthma symptoms in the past 12 months (52.6%), which was significantly higher than the percentage of Black children consistently classified as normal (35.5%, P = .049), but similar to that of Black children consistently classified as abnormal using both race-corrected and race-uncorrected equations (62.5%, P = .60). Asthma Control Test scores were not different based on classification. CONCLUSIONS: Race-correction had an extensive impact on spirometry classification in Black children, and differentially classified children had a higher rate of asthma symptoms than children consistently classified as normal. Spirometry reference equations should be reevaluated to be aligned with current scientific perspectives on the use of race in medicine.

Technical performance analysis of different types of spirometers.

BACKGROUND: The spirometer is an important element in lung function examinations, and its accuracy is directly related to the accuracy of the results of these examinations and to the diagnosis and treatment of diseases. Our aim was to conduct a performance analysis of the detection techniques of differential pressure and ultrasonic portable spirometers commonly used in China. METHODS: A standard flow/volume simulator was used to analyze the performance (accuracy, repeatability, linearity, impedance, and so on) of portable spirometers, 4 imported and 6 domestic, based on 13 curves generated by different air sources in the ISO 26782:2009 standard. A Bland-Altman diagram was used to evaluate the consistency between the values measured by the spirometers and the simulator. RESULTS: The pass rates for accuracy, repeatability, linearity, and impedance for the 10 different portable spirometers were 50%, 100%, 70%, and 70%, respectively. Only 30% (3/10) of the spirometers-2 domestic and 1 imported-met all standards of quality and performance evaluation, while the rest were partially up to standard. In the consistency evaluation, only 3 spirometers were within both the consistency standard range and the acceptability range. CONCLUSION: The quality and performance of different types of portable spirometers commonly used in the clinic differ. The use of a standard flow/volume simulator is helpful for the standard evaluation of the technical performance of spirometers.

Forced oscillatory parameters as predictors of COPD assessment test improvement in untreated COPD patients.

BACKGROUND: Few studies have examined whether baseline spirometry and the forced oscillation technique (FOT) would predict The COPD Assessment Test (CAT) score improvement after treatment of untreated COPD patients. METHODS: The study subjects included 65 untreated COPD patients. They underwent the CAT, spirometry, and FOT (MostGraph) before and after treatment for more than 2 months. In addition, recursive partitioning analysis was performed using spirometry and the FOT parameters to identify the predictors of CAT improvement (CAT score ≥2). RESULTS: CAT scores and lung function significantly improved after treatment. Recursive partitioning analysis identified 3 improved classes, defined by Rrs at 20 Hz (R20), Xrs at 5 Hz (X5), and ΔX5, but not by spirometry. The accuracy of predicting CAT improvement was as follows: odds ratio, 25.3; 95 % confidence interval, 6.1 to 104.1; sensitivity, 91.2 %; specificity, 71.0 %; positive likelihood ratio, 3.14; and negative likelihood ratio, 0.12. CONCLUSIONS: FOT helps predict improved health status in untreated COPD patients.

Spirometric reference equations for Cameroonians aged 4 to 89 years derived using lambda, mu, sigma (LMS) method.

BACKGROUND: Spirometric reference values are well known in several ethnic groups but the normative spirometric values of blacks living in Africa have been less studied. The purpose of this study is to establish normative spirometric equations from a representative population of Cameroonian children and adults and compare these equations with those developed by the Global Lung Initiative (GLI) and in Nigerians. METHODS: Spirometric data from healthy Cameroonians aged 4-89 years randomly collected between 2014 and 2018 were used to derive reference equations using generalized additive model for location (mu), shape (lambda) and scale (sigma). RESULTS: A total of 625 children and adolescents (290 males and 335 females) and 1152 adults (552 males and 600 females) were included in the study. The prediction equation for spirometric index was written as: M = Exp[a0 + a1*ln (Height) + a2*ln (Age) + Mspline, Mspline was age related spline contribution]. Applying the GLI standards for African Americans resulted in overall values greater than those found in our study for forced expiratory volume in 1s (FEV1) and forced vital capacity (FVC). These values were very close in children and adolescents while the values obtained with the GLI equations for African Americans were significantly higher in adults. FEV1/FVC ratio in our study was similar for adult males but lower in adult females (88% vs 85%, difference = + 3.5%) when applying Nigerian standards. CONCLUSIONS: FEV1 and FVC of the Cameroonian infant and adolescent population are very close to those of black Americans. However, FEV1 and FVC of Cameroonian adults are significantly lower than those of black American adults. These equations should allow a more suitable interpretation of spirometry in the Cameroonian population.

Spirometry quality predictors in a large multistate prospective study.

BACKGROUND: The Gulf Long-Term Follow-up (GuLF) Study is a prospective cohort study of health effects associated with oil spill response and clean-up following the 2010 Deepwater Horizon Disaster (DWH). As part of the study, spirometry testing of lung function was carried out in home visits across multiple states. Few studies have described factors associated with spirometry test failure in field-based settings. OBJECTIVE: Our objective was to identify what factors, if any, predict test failure among GuLF Study participants who completed spirometry testing in a non-traditional setting. METHODS: Trained examiners administered spirometry (May 2011-May 2013) to 10,019 participants living in US Gulf States (LA, MS, TX, AL, FL) using an Easy-on ultrasonic spirometer. We applied American Thoracic Society/European Respiratory Society quality criteria to determine quality test failure and identified factors predictive of failure using both a Stepwise and a LASSO model. We calculated odds ratios and 95% confidence intervals (CIs) for associations of selected factors with test failure. RESULTS: Among GuLF Study participants who conducted spirometry, self-reported African American/Black participants (OR: 1.39, 95% CI: 1.23,1.56); men (OR:1.61, 95% CI: 1.41,1.83); and those making less than $20,000 per year (OR: 1.45, 95% CI: 1.26,1.67) were more likely to fail quality testing, while those who were obese were less likely to fail (OR: 0.61, 95% CI: 0.42,0.89). CONCLUSION: Field-based studies involving spirometry should identify and account for participant factors that may influence test failure. Coaching that is tailored to those less likely to have experience with spirometry may help reduce test failure rates.

Computational tools for inversion and uncertainty estimation in respirometry.

In many physiological systems, real-time endogeneous and exogenous signals in living organisms provide critical information and interpretations of physiological functions; however, these signals or variables of interest are not directly accessible and must be estimated from noisy, measured signals. In this paper, we study an inverse problem of recovering gas exchange signals of animals placed in a flow-through respirometry chamber from measured gas concentrations. For large-scale experiments (e.g., long scans with high sampling rate) that have many uncertainties (e.g., noise in the observations or an unknown impulse response function), this is a computationally challenging inverse problem. We first describe various computational tools that can be used for respirometry reconstruction and uncertainty quantification when the impulse response function is known. Then, we address the more challenging problem where the impulse response function is not known or only partially known. We describe nonlinear optimization methods for reconstruction, where both the unknown model parameters and the unknown signal are reconstructed simultaneously. Numerical experiments show the benefits and potential impacts of these methods in respirometry.

Current limits for flowmeter resistance in metabolic carts can negatively affect exercise performance.

PURPOSE: To investigate whether a metabolic cart using a flowmeter in the upper range of accepted resistance to airflow (<1.5 cmH2 O∙L-1 ∙s-1 for flows up to 14 L∙s-1 , American Thoracic Society) negatively impacts exercise performance in healthy individuals. METHODS: 16 recreationally active males (age 25 ± 1 years, height 180 ± 6 cm, weight 73.5 ± 5.8 kg, all mean ± SD) performed two incremental tests on a bicycle ergometer on each of two visits, using a metabolic cart with a flowmeter of either low (Oxycon Pro) or high (Innocor) airflow resistance. Mouth pressures, gas exchange, blood lactate concentration [La- ], perception of breathlessness, respiratory, and leg exertion were assessed throughout the tests. RESULTS: Tests performed with the Innocor were significantly shorter (15.3 ± 3.2 vs. 15.8 ± 3.3 min, p < 0.0001) and showed higher maximal flow resistance (1.3 ± 0.2 vs. 0.3 ± 0.0 cmH2 O∙L-1 ∙s-1 , p < 0.0001). At end-exercise, peak oxygen consumption (-200 ± 220 ml.min-1 , p < 0.0001), minute ventilation (-19.9 ± 10.5 L.min-1 , p < 0.0001), breathing frequency (-5.4 ± 5.2 breaths.min-1 , p < 0.0001), heart rate (-2.1 ± 3.6 bpm, p = 0.002) and [La- ] (-0.7 ± 1.0 mmol.L-1 , p < 0.0001), but not tidal volume (-0.1 ± 0.2 L, p = 0.172) were lower with the Innocor, while the perception of breathlessness was higher (+3.8 ± 5.1 points, p < 0.0001). CONCLUSIONS: Airflow resistance in the upper range of current guidelines can significantly affect exercise performance and respiratory pattern in young, healthy males during incremental exercise. The present results indicate the need to revisit guidelines for devices used in ergospirometry.

Assessing spirometry competence through certification in community-based healthcare settings in Australia and New Zealand: A position paper of the Australian and New Zealand Society of Respiratory Science.

Spirometry has been established as an essential test for diagnosing and monitoring respiratory disease, particularly asthma and COPD, as well as in occupational health surveillance. In Australia and New Zealand, there is currently no pathway for spirometry operators in community-based healthcare settings to demonstrate spirometry competence. The Australia and New Zealand Society of Respiratory Science (ANZSRS) has identified a need for developing a pathway for operators working in community-based practices in Australia and New Zealand to demonstrate spirometry competence and certification. Spirometry certification provides evidence to patients, clients, employers and organizations that an individual has participated in an assessment process that qualifies them to perform spirometry to current international spirometry standards set out by the American Thoracic Society and the European Respiratory Society (ATS/ERS). This document describes a competence assessment pathway that incorporates a portfolio and practical assessment. The completion of this pathway and the award of certification confer an individual is competent to perform spirometry for 3 years, after which re-certification is required. The adoption of this competency assessment and certification process by specialist organizations, and the commitment of operators performing spirometry to undergo this process, will enhance spirometry quality and practice in community-based healthcare settings.

Validation of an app-based portable spirometer in adolescents with asthma.

OBJECTIVES: Objective measurements of asthma impairment could aid teens in recognition of changes in asthma status over time. Ready access to a conventional spirometer is not realistic outside of the clinical setting. In this proof-of-concept study, we compared the performance of the VitalFlo mobile spirometer to the nSpire KoKo® sx1000 spirometer for accuracy in measuring Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) in adolescents with asthma. METHODS: Two hundred forty pulmonary function measurements were collected from 48 adolescents with persistent asthma from the University of North Carolina's pediatric allergy and pulmonology subspecialty clinics. Participants performed spirometry with the nSpireKoKo® sx1000 spirometer and the VitalFlo spirometer during their clinic visits. 119 simulated FVC maneuvers were conducted on both devices to standardize measurements. Pearson correlations, Bland-Altman procedure, and two-sample comparison tests were performed to assess the relationship between the two spirometers. RESULTS: VitalFlo measurements were significantly highly correlated with nSpireKoKo® spirometer values for FEV1, (r2=0.721, [95% CI, 0.749 ± 0.120], P < 0.001) and moderately for FVC (r2= 0.617, [95% CI, 0.640 ± 0.130], P < 0.001) measurements. There were no statistically significant differences of the mean FEV1 (M = 0.00764, SD = 0.364, t(59)=0.16, P = 0.87) and FVC measurements (M = 0.00261, SD = 0.565, t(59)=0.036, P = 0.97.) between the VitalFlo and nSpireKoKo® systems. Both devices demonstrated significantly high correlation when comparing the automated FVC (r2 = 0.997, [95% CI, 1.00 ± 0.00974], P < 0.001) measurements. Bland-Altman plots did not demonstrate significant bias between devices for both FEV1 (0.00764 L) and FVC (0.00261 L) measurements. CONCLUSIONS: Lung function measurements from the VitalFlo mobile spirometer were comparable to a commercially-available spirometer commonly used in clinical settings. This validated app-based spirometer for home use has the potential to improve asthma self-management.

Impact of a supervised training course on spirometry competency for primary care pediatricians.

OBJECTIVE: Spirometry is the most commonly performed lung function test, and performance, adherence to acceptability and repeatability criteria, and accurate interpretation of results help optimize the test's usefulness. This study aimed to measure the effects of spirometry training courses supported by the Italian Pediatric Respiratory Society (IPRS) on primary care pediatricians' (PCP) knowledge of spirometry test quality, ability to interpret results, and overall degree of satisfaction with the course. METHODS: Of the six face-to-face courses, four lasted two days and two lasted one day: mean duration of theoretical lessons was five and four hours respectively; and practical sessions lasted eight and six hours, respectively. At the end of each course, participants took a learning test consisting of evaluating six flow-volume curves. Degree of satisfaction was assessed by asking participants to rank the relevance, quality, and usefulness of the course. RESULTS: 261 PCPs were involved, with most (67.43%) taking two-day courses. Nearly all participants correctly identified normal and restrictive patterns. Intrathoracic large-airway obstruction was the pattern most difficult to identify correctly (70.5% overall), whereas > 80% of the participants correctly classified artifacts, obstructive-restrictive, and obstructive patterns. Participants in longer courses reported significantly higher values on the learning score. The overall degree of satisfaction average ranged between "good" and "excellent". CONCLUSIONS: This pilot study showed the greater impact of two-day courses than one-day courses for training PCPs to properly interpret spirometry, confirming that a practical module lasting at least six hours is sufficient to deliver adequate training on spirometry for healthcare professionals.

GINA 2020: what's new and why?

The Global initiative against asthma (GINA) 2020 strategy has been released with some changes and updates. GINA recommends the continuation of medications, avoidance of nebulization and spirometry, and ensuring a written asthma action plan in COVID-19 times. GINA 2020 specifies which step of management is to be followed according to the patient's symptoms in an easy flowchart. Clinicians need to be aware of the changes and the evidence behind them.

Practical considerations for spirometry during the COVID-19 outbreak: Literature review and insights.

BACKGROUND: As the Coronavirus disease 2019 (COVID-19) is spreading worldwide, countries are dealing with different phases of the pandemic. Lately, scientific evidence has been growing about the measures for reopening respiratory outpatient services during the COVID-19 pandemic. We aim to summarize the key differences and similarities among recommendations by different national and international organizations. METHODS: We searched on Google and Pubmed for recently published National and International Recommendations/Guidelines/Position Papers from professional organizations and societies, offering a guidance to physicians on how to safely perform pulmonary function testing during COVID-19 pandemic. We also searched for spirometry manufacturers' operational indications. RESULTS: Indications on spirometry were released by the Chinese Task force, the American Thoracic Society, the European Respiratory Society, the Thoracic Society of Australia and New Zealand, the Société de Pneumologie de Langue Française, the Spanish Societies (Sociedad Espanola de Neumologia y Cirugia Toracica, Sociedad Espanola de Alergologia e Inmunologia Clinica, Asociacion de Especialistas en Enfermeria del trabajo, Asociacion de Enfermeria Comunitaria), the Sociedade Portuguesa de Pneumologia, the British Thoracic Society/Association for Respiratory Technology & Physiology, the Irish Thoracic Society, the Sociedad Uruguaya de Neumologia, the Italian Thoracic Society and the Italian Respiratory Society, Cleveland Clinic and Nebraska Medical Center. Detailed technical recommendations were found on manufacturers' websites. We found several similarities across available guidelines for safely resuming pulmonary function services, as well as differences in criteria for selecting eligible patients for which spirometry is deemed essential and advice which was not homogenous on room ventilation precautions. CONCLUSIONS: This study shows a synthesis of national/international guidelines allowing practicing physicians to adapt and shape the way to organize their outpatient services locally. There is generally good agreement on the importance of limiting pulmonary function testing to selected cases only. However, significant differences concerning the subsets of candidate patients, as well as on the management of adequate room ventilation, were observed.

Gender influence on the MVV / FEVi ratio in a population of healthy young adults.

INTRODUCTION: Maximal voluntary ventilation (MVV) and flow expiratory volume in the first second (FEVi) are important spirometric parameters. They are both gender-dependent. However, estimating the MVV, which is widely practiced in cardiopulmonary function testing, by multiplying FEVi by a constant value (equal to MVV/FEVi ratio) does not seem to take this into account. The purpose of this study was to compare the MVV/FEVi ratio by gender among healthy young adults. METHODS: This cross-sectional prospective study involved 67 medical sciences students, including 36 females of the same race, height, and age group. Their ventilatory function was assessed using a computerized spirometer, according to international recommendations. Pearson's test made it possible to correlate different spirometric parameters and linear regression was established between MVV and FEVi. The nonparametric Kruskal-Wallis test was used to compare the MVV/FEVi ratio between females and males. Comparisons by gender were made also between our data and previous prediction equations. RESULTS: In both females and males, FEVi was the spirometric parameter with which MVV had the highest correlation (r = .91 in females, r = .63 in males). A comparison of the means of the MVV/FEVi ratio by gender showed a statistically significant (p < .005) decrease in females (35.68 vs. 38.87). The previous prediction equations showed statistically significant under and overestimation of MVV values when gender was not taken into account. CONCLUSION: For the same height, age, and race, the ratio MVV/FEVi was significantly lower for females. So, the use of a preset constant value in estimating the MVV without taking gender into account was methodologically questionable. This work, which could have clinical implications, would benefit from being confirmed in a larger population.

Spirometry practice and the impact of a phase 1 training workshop among health workers in southern Nigeria: a cross-sectional study.

BACKGROUND: Global standards require that spirometry should be performed by trained and experienced personnel, who would be able to assess the correct performance of tests by patients and assure good quality of the result. The complete achievement of this requires a two-step assessment where competency in both knowledge and skills are tested. This study aims to assess the impact of a one-day hands-on spirometry training (Phase1), on the knowledge and application of spirometry among health workers. METHODS: This was a descriptive cross-sectional study, which describes a one-day (seven hours) spirometry training and skills impartation done at two conference city locations in Enugu and Calabar in the southern part of Nigeria. All the verbally consenting attendees who completed the training assessment tests constituted the study population. The assessment of the spirometry knowledge base before and after the theory and practical sessions, on the various aspects of spirometry, according to international best practices, quality assurance and the interpretation of results, was done and the outcome was analyzed. Factors that could affect the outcome were also assessed. RESULTS: There were 64 consenting participants of whom 54.7% (35/64) were females. Theparticipants demonstrated much improved post-intervention knowledge and could satisfactorily perform spirometry, calibration, interpretation of test results and quality control as evidenced by the post test scores after practical sessions were conducted. Pre-test mean scores improved by a mean difference of 12% (p < 001) and were affected by the year of academic graduation and availability of spirometers at the place of work, an effect that was no longer seen at post-test following the hands-on spirometry training. CONCLUSION: The present study has shown that a one-day spirometry workshop significantly improved the knowledge of spirometry practice. There is need to set up more frequent locally-organized spirometry workshops since a one-day seven-hour effective knowledge and practical training would most likely have significant impact on participants' spirometry practice with its expected positive outcome on respiratory health in Nigeria.

Does spirometric tests meet the acceptability criteria? Data from a tertiary chest hospital in Turkey.

INTRODUCTION: First step is to evaluate the quality of the test in interpreting spirometries. International societies have defined the acceptability criteria for spirometric tests. With this study, it was aimed to evaluate spirometric tests in terms of compliance with international acceptability criteria and to determine error types. MATERIALS AND METHODS: Spirometric manoeuvres held at a tertiary chest diseases hospital were evaluated as to whether the acceptability criteria of "American Thoracic Society/European Respiratory Society (ATS/ERS)" guideline were maintained or not. Errors determined were classified as unexplosive start of expiration, submaximal effort, cough, closure of glottis, missing closure of the loop ring and early termination of expiration. RESULT: Among tests evaluated (n= 510), 276 (54.1%) belonged to female and 234 (45.9%) to male subjects. Average age of subjects was 56.1 ± 15.0 years. It was noted that 318 (62.4%) of the tests met acceptability criteria, whereas 192 (37.6%) did not. The most frequently noted error type is submaximal effort by 30.2% followed by missing closure of the loop, early terminaton of expiration, coughing, unexplosive start of expiration and closure of glottis. In the tests whose spirometric maneuvers did not meet the criteria, the mean age of the patients was significantly higher than in the appropriate tests. When the cases were grouped according to their age, it was observed that the rate of conformity of spirometric examinations decreased significantly as the age range increased. CONCLUSIONS: Within this study it is the first time in our country that evaluation of spirometric studies has been made to see the rate of conformity with international standarts. Although it is thought that spirometric examinations are not technically appropriate in clinical practice throughout our country, there is no data in the literature. Although the center where the study is conducted is a tertiary chest diseases hospital, the data obtained reveal that in spirometric evaluations, a substantially non-standard examination was performed.

Diffusing capacity in normal-for-age spirometry and spirometric impairments, using reference equations from the global lung function initiative.

BACKGROUND: Reference equations from the Global Lung Function Initiative (GLI) are now available for both spirometry and diffusion. However, respiratory phenotypes defined by GLI-based measures of diffusion have not yet been evaluated in GLI-based normal-for-age spirometry or spirometric impairments. METHODS: We evaluated cross-sectional data from 2100 Caucasians, aged 40-85 years. GLI-based spirometric categories included normal-for-age and the impairments of restrictive-pattern and three-level severity of airflow-obstruction (mild, moderate, severe). GLI-based diffusion included diffusing capacity of the lung for carbon monoxide (DLCO) and measured components of alveolar volume (VA) and transfer coefficient (KCO): DLCO = [VA]x[KCO]. Using multivariable regression models, adjusted odds ratios (adjORs) for DLCO, VA, and KCO < lower limit of normal (LLN) were calculated for spirometric impairments, relative to normal-for-age spirometry. RESULTS: Relative to normal-for-age spirometry, the restrictive-pattern increased the adjORs (95% confidence intervals) for DLCO and VA < LLN-4.61 (3.62, 5.85) and 15.53 (11.8, 20.4), respectively, but not for KCO < LLN-1.02 (0.79, 1.33). Also relative to normal-for-age spirometry, airflow-obstruction from mild to severe increased the adjORs for DLCO < LLN-from 1.22 (0.80, 1.86) to 6.63 (4.91, 8.95), for VA < LLN-from 1.37 (0.85, 2.18) to 7.01 (5.20, 9.43), and for KCO < LLN-from 2.04 (1.33, 3.14) to 3.03 (2.29, 3.99). Notably, in normal-for-age spirometry, 34.5%, 19.7%, and 25.3% of participants had DLCO, VA, or KCO < LLN, respectively. CONCLUSION: Abnormal diffusion is most prevalent in spirometric impairments but also occurs in normal-for-age spirometry. These results further inform the respiratory phenotypes of GLI-based spirometric categories and, in turn, the spirometric evaluation of respiratory disease.

Validation of a method to assess emphysema severity by spirometry in the COPDGene study.

BACKGROUND: Standard spirometry cannot identify the predominant mechanism underlying airflow obstruction in COPD, namely emphysema or airway disease. We aimed at validating a previously developed methodology to detect emphysema by mathematical analysis of the maximal expiratory flow-volume (MEFV) curve in standard spirometry. METHODS: From the COPDGene population we selected those 5930 subjects with MEFV curve and inspiratory-expiratory CT obtained on the same day. The MEFV curve descending limb was fit real-time using forced vital capacity (FVC), peak expiratory flow, and forced expiratory flows at 25, 50 and 75% of FVC to derive an emphysema severity index (ESI), expressed as a continuous positive numeric parameter ranging from 0 to 10. According to inspiratory CT percent lung attenuation area below - 950 HU we defined three emphysema severity subgroups (%LAA-950insp < 6, 6-14, ≥14). By co-registration of inspiratory-expiratory CT we quantified persistent (%pLDA) and functional (%fLDA) low-density areas as CT metrics of emphysema and airway disease, respectively. RESULTS: ESI differentiated CT emphysema severity subgroups increasing in parallel with GOLD stages (p < .001), but with high variability within each stage. ESI had significantly higher correlations (p < .001) with emphysema than with airway disease CT metrics, explaining 67% of %pLDA variability. Conversely, standard spirometric variables (FEV1, FEV1/FVC) had significantly lower correlations than ESI with emphysema CT metrics and did not differentiate between emphysema and airways CT metrics. CONCLUSIONS: ESI adds to standard spirometry the power to discriminate whether emphysema is the predominant mechanism of airway obstruction. ESI methodology has been validated in the large multiethnic population of smokers of the COPDGene study and therefore it could be applied for clinical and research purposes in the general population of smokers, using a readily available online website.