Bronchial anthracofibrosis (BAF), which is associated with exposure to biomass smoke in inefficiently ventilated indoor areas, can take the form of obstructive lung disease. Patients with BAF can mimic or present with an exacerbation of chronic obstructive pulmonary disease (COPD). The purpose of the current study was to investigate the prevalence of BAF in Korean patients with COPD exacerbation as well as to examine the clinical features of these patients in order to determine its clinical relevance.
A total of 206 patients with COPD exacerbation were divided into BAF and non-BAF groups, according to computed tomography findings. We compared both clinical and radiologic variables between the two groups.
Patients with BAF (51 [25%]) were older, with a preponderance of nonsmoking women; moreover, they showed a more frequent association with exposure to wood smoke compared to those without BAF. However, no differences in the severity of illness and clinical course between the two groups were observed. Patients in the BAF group had less severe airflow obstruction, but more common and severe pulmonary hypertension signs than those in the non-BAF group.
Compared with non-BAF COPD, BAF may be associated with milder airflow limitation and more frequent signs of pulmonary hypertension with a more severe grade in patients presenting with COPD exacerbation.
Bronchial anthracofibrosis (BAF) is characterized by definite narrowing or obliteration of large airways with anthracotic pigmentation in the bronchial mucosa
BAF is frequently associated with tuberculosis, pneumonia, lung cancer, and chronic obstructive pulmonary disease (COPD)
Between August 2008 and April, 2012, a cohort of COPD exacerbation hospitalized to the Kyungpook National University Hospital (KNUH), a tertiary referral center (Daegu, Korea) were analyzed retrospectively. This study was approved by the Institutional Review Board of the KNUH, which waived the requirement for written informed consent because of the retrospective nature of the study. According to the criteria of the Global Initiative for Chronic Obstructive Lung Diseases
The diagnosis of BAF was based on the CT findings that fulfilled the following criteria: 1) bronchostenosis that caused smooth narrowing of multiple lobar or segmental bronchi; 2) calcified or non-calcified lymph node enlargement adjacent to narrowed bronchi; and 3) these two criteria which could not be attributed to other causes (
Demographic and clinical variables of the patients were checked, including gender, age, smoking history, body mass index, and comorbid conditions. History of exposure to wood smoke and its duration was retrospectively taken by an interviewer over the phone. For severity of illness, BAP-65 classes were assessed
PFT data were obtained according to the standards of the American Thoracic Society and European Respiratory Society Guideline
CT scans were reviewed by two radiologists and a consensus diagnosis was reached. In addition to the presence of BAF, we checked for the presence of consolidation, GGO, bronchiolitis, emphysema, bronchiectasis, bronchial wall thickening, pleural effusion, and inactive pulmonary tuberculosis. These CT findings were defined as follows: consolidation as airspace opacification with obscuration of the underlying vasculature
To determine the prevalence of pulmonary hypertension, we measured main PA size and PA-to-ascending aorta (AA) ratio. Similar to previous studies
Transthoracic echocardiographic findings, including right ventricular (RV) dysfunction and RV systolic pressure (RVSP), were also reviewed. RV dysfunction was defined as RV free wall hypokinesia, and RVSPs were calculated using tricuspid regurgitation flow velocity as determined by Doppler echocardiography
SPSS ver. 12.0 (SPSS Inc., Chicago, IL, USA) was used in performance of statistical analyses. The data are expressed as the mean±standard deviation or median with interquartile range (IQR), if the data were skewed for continuous variables and number with percentage for categorical variables. Kappa statistic was used for measurement of the agreement between bronchoscopy and CT in determining the presence of BAF. Between the two groups, continuous variables were compared using the Student's t-test or the Mann-Whitney U test, whereas categorical variables were compared using either chi-squared test or Fisher's exact test.
Blinded to bronchoscopic finding, radiologists determined the presence or absence of BAF based on CT findings in 30 patients for whom both bronchoscopic results and CT images were available. Kappa statistic for diagnosing was 0.933 between bronchoscopy and CT. Initially, 209 patients were included in this study but three were excluded due to stage III or IV lung cancer (n=2) or pneumoconiosis (n=1). Consequently, a total of 206 patients were included in the final analysis and 51 (25%) were diagnosed as having BAF based on CT scan.
Patients with BAF were significantly older (78±7.6 years vs. 71±9.8 years, p<0.001) with female preponderance (61% vs. 23%, p<0.001) (
Respiratory tract infection, including tracheobronchitis and pneumonia, was the most common cause of COPD exacerbation in both groups, however, its frequency was significantly lower in the BAF group, compared with the non-BAF group (77% vs. 90%, p=0.011) (
Peripheral blood WBC count and blood levels of ESR, CRP, procalcitonin, troponin-I, and D-dimer did not differ significantly between the two groups (
Of various CT findings, frequencies of emphysema and bronchial wall thickening were significantly greater in the non-BAF group, compared with the BAF group (80% vs. 33%, p<0.001; and 92% vs. 73%, p<0.001, respectively) (
Echocardiographic pulmonary hypertension was frequently observed in the BAF group, as compared with the non-BAF group (50% [6/12] vs. 18% [6/33], p=0.033), although echocardiographic data were available in the minority of the patients.
In the current study, approximately 25% of Korean patients with COPD exacerbation had CT findings consistent with BAF. The current data demonstrated that in Korea, BAF is common in nonsmoking elderly women and that among patients presenting with COPD exacerbation, the severity of illness and clinical course are similar regardless of BAF. Of note, patients with BAF had milder airflow limitation, compared to those without BAF. However, signs of pulmonary hypertension were more common with a more severe grade in the BAF group, compared with the non-BAF group.
In developing countries, such as Mexico and Columbia, where biomass fuel has been used for heating and cooking in poorly ventilated spaces, a considerable number of patients with obstructive airway disease, particularly in nonsmoking elderly females, are caused by exposure to wood smoke
Patients with BAF had less severe airflow limitation, compared to those without BAF. This finding corresponds to the previous report
It is noteworthy that the BAF group more frequently had signs of pulmonary hypertension and more severe degree of pulmonary hypertension than the non-BAF group. This is in an agreement with a necropsy finding where intimal thickening was more severe in the biomass smoke-induced COPD group, compared with the cigarette smoke-induced COPD group
Whether BAF is a phenotype of COPD or a distinct entity remains to be clarified. Biomass smoke, such as wood smoke, is considered a risk factor for COPD. However, BAF is thought be one end of the spectrum of wood smoke-induced lung diseases
Several limitations of the current study should be considered. First, although bronchoscopy is needed to confirm BAF, the diagnosis was based on CT findings in this study. However, the CT findings of BAF are well-established, and agreement rate between bronchoscopy and CT scan in diagnosis of BAF was high for 30 patients whose bronchoscopic data were available. Second, as this study was retrospective, some clinical data were not available. Thus, selection bias could not be avoided. Third, history of exposure to wood smoke and its duration was taken by an interviewer over the phone. Recall bias should be considered. Finally, as our criteria for tracheobronchitis and pneumonia were broad, there is a possibility that the frequencies were overestimated.
In conclusion, BAF should be considered in Korean patients with presenting with COPD exacerbation, particularly in nonsmoking elderly females with a history of exposure to wood smoke. Compared with non-BAF COPD, BAF is characterized by less frequent emphysema and bronchial wall thickening on CT scan, less severe airflow limitation, and more common pulmonary hypertension with a greater degree of severity. From these results, BAF is a distinct phenotype of obstructive lung disease.
This research was supported by Kyungpook National University Research Fund, 2012.
No potential conflict of interest relevan to this article was reported.
On the computed tomography scan, bronchial anthracofibrosis is characterized by smooth narrowing and thickening of multiple lobar or segmental bronchi (white arrowheads) and calcified lymph node enlargement adjacent to the narrowed bronchi (black arrows) with or without lobar or segmental atelectasis (white arrow).
The diameter of the main pulmonary artery (PA) and the diameter of the ascending aorta (AA) are measured at the level of the PA bifurcation.
Clinical characteristics of patients (n=206)
Values are presented as mean±standard deviation, median (interquartile range), number (%) or number/number (%).
BAP-65, severity of illness score based on the presence of blood urea nitrogen≥24 mg/dL, altered mental status, pulse≥109 beats/min, or age>65 years.
BAF: bronchial anthracofibrosis; COPD: chronic obstructive pulmonary disease.
Laboratory and spirometric data
Values are presented as mean±standard deviation or median (interquartile range).
BAF: bronchial anthracofibrosis; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate; NT-proBNP: N-terminal-pro-B-type natriuretic peptide; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity.
Computed tomographic and echocardiographic findings
Values are presented as mean±standard deviation, median (interquartile range) or number (%).
BAF: bronchial anthracofibrosis; CT: computed tomography; PA-to-AA ratio: ratio of diameter of main pulmonary artery and diameter of ascending aorta; RVSP: right ventricular systolic pressure; RV: right ventricular.