Chest
Volume 130, Issue 1, July 2006, Pages 108-118
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Original Research
Advanced Emphysema in African-American and White Patients: Do Differences Exist?

https://doi.org/10.1378/chest.130.1.108Get rights and content

Background

Emphysema is the only smoking-related disease in which white patients have higher prevalence and higher attributable mortality rates than African-American patients. Epidemiologic studies have not addressed, nor explained, the observed racial differences in emphysema.

Study objectives

To determine whether white and African-American patients differ with respect to the magnitude, anatomic distribution, and physiologic impairments of emphysema.

Patients

Characteristics of patients with severe and very severe emphysema enrolled in the National Emphysema Treatment Trial were examined and compared. Patient demographics, cardiopulmonary function, quality of life, and severity/distribution of the emphysema by quantitative CT were analyzed.

Results

Of the 1,218 patients enrolled in the trial, 42 were African American (3.4%) and 1,156 were white (95%). African Americans were younger (mean age ± SD, 63 ± 7 years vs 67 ± 6 years) and smoked less (26 ± 14 cigarettes per day vs 32 ± 14 cigarettes per day) than white patients (p = 0.01). There was no difference between the two racial groups in pulmonary function (FEV1, 27 ± 6% predicted vs 27 ± 7% predicted), gas exchange (Pao2, 66 ± 11 mm Hg vs 65 ± 10 mm Hg), and exercise (33 ± 14 W vs 36 ± 21 W), respectively. Quality of life measures were similar between the groups, but African Americans had a lower socioeconomic status, lower education level, and fewer were married. Radiographic analysis of the extent of emphysema in African Americans, who were matched with selected white patients, revealed significantly less emphysema in the former group and different distribution of severe emphysema.

Conclusions

African Americans with emphysema were younger and had a similar degree of lung impairment as the white study population despite smoking less. In a subgroup of matched patients, the severity and distribution of emphysema by quantitative radiographic analysis were different.

Section snippets

Materials and Methods

The NETT is a multicenter, randomized clinical trial of optimal medical therapy vs optimal medical therapy plus lung volume reduction surgery in the treatment of severe emphysema. The design and methods of the NETT have been described previously and are summarized below.11 All analyzed data were obtained from the baseline prerehabilitation assessment during the first or second visit to NETT centers, except for some chest CT scans that were collected after rehabilitation.

Patient Selection

The inclusion criteria were as follows: FEV1 ≤ 45% of predicted value, and if age ≥ 70 years, FEV1 ≥ 15% of predicted; total lung capacity (TLC) ≥ 100% of predicted; residual volume (RV) ≥ 150% of predicted; Paco2 ≤ 60 mm Hg (≤ 55 mm Hg in Denver), with patients at rest and breathing room air; Pao2 ≥ 45 mm Hg (≥ 30 mm Hg in Denver), with patients at rest and breathing room air; ability to walk > 140 m (459 feet) in 6 min; ability to complete 3 min of pedaling on a bicycle ergometer without a

Patient Data

The initial evaluation included 6-min walk distance15; postbronchodilator pulmonary function tests; maximal exercise capacity during cycle ergometry while receiving 30% oxygen; echocardiography; radionuclide pharmacologic (dobutamine) cardiac stress testing; arterial blood gas measurement; and lung perfusion scanning. Patients also responded to a battery of general and disease-specific self- administered quality of life scales16: the Quality of Well-being (QWB) scale, the Short Form-36, St.

Diagnostic Imaging Studies

The severity and distribution of emphysema were determined from CT scans of the chest obtained during full inspiration. Spiral CT scans were acquired with a collimation ranging from 3 to 10 mm, with the majority of the centers having a slice collimation ≤ 5 mm. Data were evaluated using the standard reconstruction kernel but were not complete for all patients because of early archiving problems, not meeting a set of minimum criteria for matching the prescribed scanning protocol, or missing

Statistical Analysis

Categorical variables were compared using χ2 and Fisher Exact Test. Continuous variables (age, FEV1, TLC, RV) were compared using two-way analysis of variance to evaluate differences between gender and race, and multiple pair-wise comparisons used the Dunn-Bonferroni adjustment to maintain an experiment-wise type I error ≤ 0.05. Prior to analysis, continuous data were tested for normality using the Shapiro-Wilk test. If the data for the continuous dependent variables were significantly

Demographic and Physiologic Racial Differences

Between January 1998 and July 2002, a total of 1,218 patients with severe emphysema were enrolled in the NETT. Forty-two of the patients (3.4%) were African American, and 1,156 patients (95%) were white. The baseline characteristics of these patients are shown in Table 1. African Americans were younger and less heavy. There was no difference in the severity of the emphysema based on static pulmonary function, gas exchange, exercise performance, and use of steroids. African-American patients in

Discussion

Our data show that African-American patients with advanced emphysema presented with impairment comparable to white patients as identified by lung function, exercise, and quality of life measures, and at a younger age despite smoking less. Each gender within the two racial groups was as affected as its counterpart; African-American women were not less severely sick than white women. However, when matched with respect to age, height, smoking, and pulmonary function, African-American patients

Source of Funding

The NETT is supported by contracts with the National Heart, Lung, and Blood Institute (N01HR76101, N01HR76102, N01HR76103, N01HR76104, N01HR76105, N01HR76106, N01HR76107, N01HR76108, N01HR76109, N01HR76110, N01HR76111, N01HR76112, N01HR76113, N01HR76114, N01HR76115, N01HR76116, N01HR76118, and N01HR76119), the Centers for Medicare and Medicaid Services (formerly the Health Care Financing Administration); and the Agency for Healthcare Research and Quality.

Office of the Chair of the Steering Committee

University of Pennsylvania,

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  • Cited by (0)

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

    Details of National Emphysema Treatment Trial membership and locations are given in the Appendix.

    Dr. Hoffman is a shareholder of VIDA Diagnostics, which seeks to commercialize the software that may be relevant to this article.

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