Is There a Role for Using Race-Specific Reference Equations? Yes and No

Comparison of Race-Neutral versus Race-Specific Spirometry Equations for Evaluation of Child Asthma

Rationale: Race-based estimates of pulmonary function in children could influence the evaluation of asthma in children from racial and ethnic minoritized backgrounds. Objectives: To determine if race-neutral (Global Lung Function Initiative [GLI]-Global) versus race-specific (GLI-Race-Specific) reference equations differentially impact spirometry evaluation of childhood asthma. Methods: The analysis included 8,719 children aged 5 to <12 years from 27 cohorts across the United States grouped by parent-reported race and ethnicity. We analyzed how the equations affected FEV1, FVC, and FEV1/FVC z-scores. We used multivariable logistic models to evaluate associations between z-scores calculated with different equations and asthma diagnosis, emergency department visits, and hospitalization. Measurements and Main Results: For Black children, the GLI-Global versus GLI-Race-Specific equations estimated significantly lower z-scores for FEV1 and FVC but similar values for FEV1/FVC, thus increasing the proportion of children classified with low FEV1 by 14%. Although both equations yielded strong inverse relationships between FEV1 and FEV1/FVC z-scores and asthma outcomes, these relationships varied across racial and ethnic groups (P < 0.05). For any given FEV1 or FEV1/FVC z-score, asthma diagnosis and emergency department visits were higher among Black and Hispanic than among White children (P < 0.05). For FEV1, GLI-Global equations estimated asthma outcomes that were more uniform across racial and ethnic groups. Conclusions: Parent-reported race and ethnicity influenced relationships between lung function and asthma outcomes. Our data show no advantage to race-specific equations for evaluating childhood asthma, and the potential for race-specific equations to obscure lung impairment in disadvantaged children strongly supports using race-neutral equations.

PM2.5 exposure and household income are associated with lung function abnormalities in children with sickle cell disease

RATIONALE

Cardiopulmonary dysfunction is a major contributor to mortality among persons with sickle cell disease (pwSCD). Despite this, little is known regarding environmental drivers of lung function decline.

OBJECTIVE

We hypothesized that environmental and socioeconomic variables have a significant effect on lung function in pwSCD that can be detected by spirometry.

METHODS

We retrospectively analyzed all spirometry results from pwSCD followed in the Pediatric Pulmonology clinic at the Children's Hospital of Philadelphia since 1 January 2016.

RESULTS

The study included 349 spirometry tests from 128 patients, primarily "Black or African American" (88%) and male (61%). More frequent exposure to PM2.5 above 25 μg/m3 was associated with higher odds of obstruction. Specifically, when compared to incidence of exposure to PM2.5 above 25 μg/m3 <25th percentile, both pwSCD exposed to 25th-75th percentile and pwSCD >75th percentile had higher odds of obstruction on spirometry (25th-75th: odds ratio [OR]: 9.6, p = .017; >75th: OR: 31.85, p = .002) despite correction for potential confounders. Similarly, median household income below the mean was associated with higher odds of restriction (OR: 4.37; p = .009).

CONCLUSIONS

We report higher odds of obstruction in pwSCD frequently exposed to PM2.5 concentrations above 25 μg/m3 and higher odds of restriction in pwSCD with lower household income. Our findings link spirometry patterns to modifiable risk factors indicating that there may opportunities for early intervention in pwSCD that have been referred to a pulmonology clinic. Further research is needed to assess if these findings can be generalized to the wider population of pwSCD.

The prevalence and mortality risks of PRISm and COPD in the United States from NHANES 2007-2012

BACKGROUND

We estimated the prevalence and mortality risks of preserved ratio impaired spirometry (PRISm) and chronic obstructive pulmonary disease (COPD) in the US adult population.

METHODS

We linked three waves of pre-bronchodilator spirometry data from the US National Health and Nutritional Examination Survey (2007-2012) with the National Death Index. The analytic sample included adults ages 20 to 79 without missing data on age, sex, height, BMI, race/ethnicity, and smoking status. We defined COPD (GOLD 1, 2, and 3-4) and PRISm using FEV1/FVC cut points by the Global Initiative for Chronic Obstructive Lung Disease (GOLD). We compared the prevalence of GOLD stages and PRISm by covariates across the three waves. We estimated adjusted all-cause and cause-specific mortality risks by COPD stage and PRISm using all three waves combined.

RESULTS

Prevalence of COPD and PRISm from 2007-2012 ranged from 13.1%-14.3% and 9.6%-10.2%, respectively. We found significant differences in prevalence by sex, age, smoking status, and race/ethnicity. Males had higher rates of COPD regardless of stage, while females had higher rates of PRISm. COPD prevalence increased with age, but not PRISm, which was highest among middle-aged individuals. Compared to current and never smokers, former smokers showed lower rates of PRISm but higher rates of GOLD 1. COPD prevalence was highest among non-Hispanic White individuals, and PRISm was notably higher among non-Hispanic Black individuals (range 31.4%-37.4%). We found associations between PRISm and all-cause mortality (hazard ratio [HR]: 2.3 95% CI: 1.9-2.9) and various cause-specific deaths (HR ranges: 2.0-5.3). We also found associations between GOLD 2 (HR: 2.1, 95% CI: 1.7-2.6) or higher (HR: 4.2, 95% CI: 2.7-6.5) and all-cause mortality. Cause-specific mortality risk varied within COPD stages but typically increased with higher GOLD stage.

CONCLUSIONS

The prevalence of COPD and PRISm remained stable from 2007-2012. Greater attention should be paid to the potential impacts of PRISm due to its higher prevalence in minority groups and its associations with mortality across various causes including cancer.

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.

Race-Specific Interpretation of Spirometry: Impact on the Lung Allocation Score

Rationale: Interpretation of spirometry using race-specific reference equations may contribute to health disparities via underestimation of the degree of lung function impairment in Black patients. The use of race-specific equations may differentially affect patients with severe respiratory disease via the use of percentage predicted forced vital capacity (FVCpp) when included in the lung allocation score (LAS), the primary determinant of priority for lung transplantation. Objectives: To determine the impact of a race-specific versus a race-neutral approach to spirometry interpretation on the LAS among adults listed for lung transplantation in the United States. Methods: We developed a cohort from the United Network for Organ Sharing database including all White and Black adults listed for lung transplantation between January 7, 2009, and February 18, 2015. The LAS at listing was calculated for each patient under race-specific and race-neutral approaches, using the FVCpp generated from the Global Lung Function Initiative equation corresponding to each patient's race (race-specific) or from the Global Lung Function Initiative "other" (race-neutral) equation. Differences in LAS between approaches were compared by race, with positive values indicating a higher LAS under the race-neutral approach. Results: In this cohort of 8,982 patients, 90.3% were White and 9.7% were Black. The mean FVCpp was 4.4% higher versus 3.8% lower among White versus Black patients (P < 0.001) under a race-neutral compared with a race-specific approach. Compared with White patients, Black patients had a higher mean LAS under both a race-specific (41.9 vs. 43.9; P < 0.001) and a race-neutral (41.3 vs. 44.3; P < 0.001) approach. However, the mean difference in LAS under a race-neutral approach was -0.6 versus +0.6 for White versus Black patients (P < 0.001). Differences in LAS under a race-neutral approach were most pronounced for those in group B (pulmonary vascular disease) (-0.71 vs. +0.70; P < 0.001) and group D (restrictive lung disease) (-0.78 vs. +0.68; P < 0.001). Conclusions: A race-specific approach to spirometry interpretation has potential to adversely affect the care of Black patients with advanced respiratory disease. Compared with a race-neutral approach, a race-specific approach resulted in lower LASs for Black patients and higher LASs for White patients, which may have contributed to racially biased allocation of lung transplantation. The future use of race-specific equations must be carefully considered.

Obesity-related Changes in Diffusing Capacity and Transfer Coefficient of the Lung for Carbon Monoxide and Resulting Patterns of Abnormality across Reference Equations

Rationale: In 2017, an American Thoracic Society/European Respiratory Society Task Force report recommended further research on the effects that body mass index (BMI) has on diffusing capacity of the lung for carbon monoxide (DlCO), the transfer coefficient (Kco), and the alveolar volume (VA). Objectives: Our goals were to 1) quantify the magnitude and direction of change to measured and predicted DlCO values as BMI increases in patients free of cardiopulmonary disease and 2) identify how BMI and obesity-related changes differ by reference set. Methods: Using data from a prospective cohort study of service members free of cardiopulmonary disease, we modeled the effect that BMI has on measured values of DlCO, Kco, and VA, after adjusting for age, sex, hemoglobin (Hgb), and height. We then referenced DlCO, Kco, and VA to normal values using four different reference equations. Results: There were 380 patients with data available for analysis, and 130 had a BMI ⩾ 30 kg/m2 (87.7% class I obesity). After controlling for age, sex, Hgb, and height, increased BMI was significantly associated with Kco (β = 0.09, P < 0.01) and VA (β = -0.15, P < 0.01) but not DlCO. After adjustment for Hgb, for every 5-kg/m2 increase in BMI, the mean increase in percent predicted (PPD) values ranged from 4.2% to 6.5% and from 5.0% to 7.5% for DlCO and Kco, respectively; and the mean decrease in VA PPD was 3.2-4.0%. In the presence of obesity (BMI ⩾ 30 kg/m2), the prevalence of DlCO and Kco abnormalities dropped by 4.1-12.1% and 0.4-16.3%, respectively, across equations, whereas VA abnormalities increased from 7.7% to 9.9%. Eliminating 163 patients with abnormal trans-thoracic echocardiogram (TEE), high-resolution computed tomographic (HRCT) scan, or Hgb altered the magnitude of relationships, but significance was preserved. Conclusions: In an otherwise healthy population with predominantly class I obesity and normal TTE, HRCT scan, and Hgb, we found that Kco and VA were more affected by BMI than DlCO. Increases in PPD values varied across equations and were modest but significant and could change clinical decision making by reducing sensitivity for detecting gas-exchange abnormalities. BMI and obesity had the smallest effect on Global Lung Function Initiative PPD values.

Changes in interpretation of spirometry by implementing the GLI 2012 reference equations: impact on patients tested in a hospital-based PFT lab in a large metropolitan city

BACKGROUND

The Global Lung Function Initiative (GLI-2012) focused on race/ethnicity as an important factor in determining reference values. This study evaluated the effects of changing from Canadian reference equations developed from an all-Caucasian cohort with European ancestry to the GLI-2012 on the interpretation of spirometry in a multiethnic population and aimed to identify the ethnic groups affected by discrepant interpretations.

METHODS

Clinically indicated spirometry in a multiethnic population (aged 20-80 years) collected from 2018 to 2021 was analysed. The predicted and lower limit of normal (LLN) values were calculated using three sets of reference equations: Canadian, GLI-race/ethnic-based (GLI-Race) and GLI-race/ethnic-neutral (GLI-Other). We compared the prevalence of concordance in the abnormal diagnoses (defined as <LLN) for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and FEV₁/FVC among the three reference values, and evaluated whether race/ethnicity was associated with discordance.

RESULTS

Data from 406 participants were evaluated (non-Caucasian 43.6%). There was 85%-87% concordance for normal/abnormal FVC and FEV₁ interpretations among the Canadian, GLI-Race and GLI-Other reference equations. In all ethnic groups, application of the Canadian references for interpretation led to a higher prevalence of abnormal (<LLN) FVC and FEV₁compared with GLI-Race and GLI-Other. This trend was more prominent in Black, South-East Asian and Mixed/other ethnic groups when comparing the Canadian to the GLI-Race equations. In contrast, the discordance rates were similar among ethnic groups when compared with the GLI-Other reference equations. Interpretation of FEV₁/FVC had a high rate of agreement among all equations.

CONCLUSION

Interpretation using Canadian reference equations was associated with a higher prevalence of restrictive physiology compared with the GLI-2012 equations, particularly if the GLI-Race were used. These observations were mostly found in non-white Caucasian groups, highlighting the need to choose reference equations that reflect closely the ethnic mix of the population being evaluated in order to optimise patient management.