Incremental value of oblique chest radiographs in the diagnosis of asbestos-induced pleural disease

To assess the value of oblique chest radiographs in the diagnosis of asbestos-related pleural disease, we identified 100 asbestos-exposed construction workers and provided separate interpretations of the postero-anterior (PA), left anterior oblique (LAO), and right anterior oblique (RAO) projections using the International Labour Office (ILO) system. We found that the LAO projection identified left-sided pleural thickening more effectively than the PA view and the RAO view improved diagnosis of right-sided disease comparably. Of 62 cases of bilateral pleural thickening, only 43 (68%) were diagnosed by the PA projection alone. The increased diagnostic efficiency of approximately 50% in identifying bilateral pleural thickening appears to justify the routine use of oblique chest films in screening asbestos-exposed populations. Since bilateral pleural thickening among asbestos-exposed workers is an indicator of significant asbestos exposure and increased risk of other asbestos-induced conditions, early detection of this abnormality can lead to interventions designed to reduce asbestos-related morbidity and mortality.     

High-resolution computed tomography in the early detection of asbestosis

Summary A group of 21 former asbestos sprayers was studied with high-resolution computed tomography (HRCT), and the findings were compared with radiographic, exposure and lung function variables. HRCT was superior to plain radiography in detecting parenchymal and pleural changes. It showed changes indicative of lung fibrosis, especially septal lines and parenchymal bands, in 9 of the 12 subjects (75%) with a plain radiographic category of 0/0 in the International Labour Office (ILO) 1980 classification of radiographs of pneumoconioses. The HRCT findings were classified according to a method developed by the authors, and an HRCT parenchymal score was calculated. The HRCT revealed pleural plaques in 19 of the 21 (90%) asbestos sprayers, whereas plain radiography detected pleural plaques in only 5 (24%) sprayers. Changes in the visceral pleura were detected twice as often with HRCT as with plain radiography. In the group without radiographic evidence of lung fibrosis (ILO < 1/0) and without evidence of emphysema in either the radiographs or the HRCT examination, there was a correlation between the HRCT parenchymal score and diffusion capacity (r = –0.64, P = 0.03) and total lung capacity (r = –0.61, P = 0.04). This finding indicates that parenchymal changes seen only with HRCT are of clinical importance. The study strongly suggests that for asbestos exposed workers with an ILO classification of < 1/0 and functional impairment, an HRCT examination should always be considered.     

Asbestos exposure: A potential cause of retroperitoneal fibrosis

The etiology of retroperitoneal fibrosis is unknown in 70% of the cases. The aim of our study was to examine the possible association between occupational asbestos exposure and retroperitoneal fibrosis; only two cases have been reported in the literature. We gathered all the cases of retroperitoneal fibrosis diagnosed in the Tampere University Hospital between 1987 and 1995. We examined their hospital records to evaluate the possible etiology of the disease. We also sent a structured questionnaire to all living patients (10/13) to obtain information on their asbestos exposure. The chest radiographs of the patients were re-read to evaluate possible changes resulting from asbestos exposure. We found 13 cases of idiopathic retroperitoneal fibrosis. Seven patients (all male) had been exposed to asbestos in the past. The chest radiographs of the four most-exposed patients showed characteristic asbestos-related abnormalities, including bilateral pleural plaques, round atelectasis and small irregular lung opacities. In our study, we found that asbestos exposure and asbestos-induced changes in the lung and pleura were common among male retroperitoneal fibrosis patients. We suggest that occupational exposure to asbestos may be an important etiological factor for retroperitoneal fibrosis. Am. J. Ind. Med. 33:418–421, 1998. © 1998 Wiley-Liss, Inc.     

The national sheet metal worker asbestos disease screening program: Radiologic findings

This report presents data gathered from a series of asbestos disease screening examinations of 9,605 United States sheet metal workers who were first employed in the trade at least 20 years before the examination. The overall prevalence of asbestos-related radiographic changes was 31.1%: 18.8% had pleural abnormalities alone, 6.6% had parenchymal abnormalities (International Labour Office (ILO) score of 1/0 or higher) © 1994 Wiley-Liss, Inc.     

The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan

BACKGROUND: Since asbestos has been widely used in Japanese building materials since 1960s, a large number of Japanese construction workers may be exposed to asbestos occupationally. METHODS: Among 2951 construction workers in Okayama, Japan, the prevalence of asbestos-induced pleural or pulmonary changes was examined by screening chest x-rays; these findings were confirmed by computed tomography (CT) scanning of the chest. RESULTS: Among 2951 construction workers, 168 (5.7%) were found to have significant findings for pleural plaque or pulmonary changes on chest x-ray. Seventy-four had both pleural plaque and asbestosis, 85 pleural plaques alone, and 9 asbestosis alone. In 11 subjects, pleural plaques were suggested by chest x-ray, but neither pleural plaque nor asbestosis was demonstrated by chest CT. Honeycombing as one of the characteristic findings of asbestosis was found in 29 subjects. Others showed subpleural spots or curvilinear shadow, which suggested the early stage of asbestosis. The occupations of these workers were carpenters (64), plasterers (27), and concrete board cutters (14). About 30% of the workers with these findings were aware that they were handling asbestos in activities such as installation of asbestos boards, and/or asbestos spraying. CONCLUSIONS: As the incidence of malignant mesothelioma and primary lung cancer associated with asbestos exposure are high, screening by chest CT is necessary for detecting asbestos-induced pulmonary and/or pleural lesions. Education for protection such as telling about the presence of asbestos in building materials is also necessary.     

Diffuse pleural fibrosis--an unreliable indicator of heavy asbestos exposure?

OBJECTIVES: This study aimed at testing the hypothesis that diffuse pleural fibrosis is associated with a heavier exposure to asbestos than that of benign pleural plaques, and hence diffuse pleural fibrosis can be used as a marker of heavy exposure. METHODS: Asbestos burden was estimated for 192 naval dockyard workers (96 with diffuse pleural fibrosis, 96 with plaques) by calculating the exposure ratings from the trade and the years spent in that trade. In 53 cases the diffuse pleural fibrosis was bilateral. RESULTS: No difference was found in the mean estimated asbestos burden between all diffuse pleural fibrosis and plaques, nor between plaques and unilateral and bilateral diffuse pleural fibrosis, analyzed separately by a one-factor analysis of variance. The mean asbestos burden was significantly greater for bilateral than for unilateral diffuse pleural fibrosis. A wide spread of asbestos exposure was noted among the men with diffuse pleural fibrosis. CONCLUSIONS: Diffuse pleural fibrosis may arise after widely varying exposure to asbestos. The mean exposure ratings for diffuse pleural fibrosis do not differ from those for pleural plaques, although the ratings are significantly higher for men with bilateral diffuse pleural fibrosis than for those with unilateral diffuse pleural fibrosis. Diffuse pleural fibrosis cannot be used as a reliable marker of heavy asbestos exposure.     

Parenchymal and pleural fibrosis in construction workers.

Exposure to mineral dust was studied among construction workers (N = 437) with the aid of a questionnaire and a chest X-ray examination of the lungs. The results of the questionnaire showed that 81% of the construction workers had been exposed to asbestos. Exposure had occurred in all of the occupational groups studied. Pleural plaques and/or lung fibrosis (ILO greater than or equal to 1/1) were found in 26% of the examined workers; the prevalence varied from 18 to 40% among the various occupational groups. Comparison with a representative sample of the Finnish male population from another investigation indicates that the frequency of lung fibrosis (ILO greater than or equal to 1/1) is at least two times higher among the examined construction workers than among the general population. It seems likely that exposure to asbestos dust can be considered an etiological factor for an appreciable number of the X-ray findings.     

Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking

A cohort of 1,117 asbestos insulation workers was established in 1963 and has been prospectively followed since then. Chest X-ray abnormalities detected at the initial medical examination, and interpreted according to the International Labour Office Classification of Radiographs of Pneumoconioses are reported in this paper. The prevalence of all radiographic abnormalities (pleural and pulmonary) increased with duration from onset of asbestos exposure. A positive smoking history was associated with a significantly higher prevalence of small irregular opacities indicating interstitial pulmonary fibrosis. Such an association was not found for pleural fibrosis. The possible mechanisms which underlie the effect of smoking on asbestos-induced interstitial fibrosis seem to be of much less importance in the development of pleural fibrosis. Progression of radiographic changes over the 20-year interval 1963-1983 will be separately reported as will the predictive significance of these changes.     

Relation of spirometric function to radiographic interstitial fibrosis in two large workforces exposed to asbestos: an evaluation of the ILO profusion score.

OBJECTIVES: To analyse quantitatively the relations of spirometric lung function (forced vital capacity (FVC)) to radiographic interstitial pulmonary fibrosis (assessed by the International Labour Organisation (ILO) profusion score of small irregular opacities) in two large workforces exposed to different intensities of asbestos. These analyses consider the question whether a similar profusion score n differently exposed workers is associated with a similar effect on lung function. METHODS: Surveys of two workforces, insulators (n = 2611) and sheet metal workers (n = 1245), by the same investigators allowed comparison of the effects of the two levels of exposure to asbestos. The two groups were of similar age and had similar percentages of non-smokers and smokers. All radiographs were read by the same expert reader. RESULTS: Consistent with their less continuous and less intense exposure to asbestos, metal workers had: (a) far less frequent radiographic asbestosis (profusion score > or = 1/0, 17.5% v 59.6% for insulators): (b) less severe radiographic asbestosis (only 1.1% had scores > or = 2/1 v 13.3% of insulators); (c) a similar slope to that seen in insulators for the relation between FVC and profusion score when pleural thickening was absent; (d) less frequent pleural fibrosis (36% v 75%); and (e) less frequent restrictive impairment (23% v 33%). In both insulators and metal workers, lung function was below normal even when lung fields were normal, FVG fell with increasing profusion, it was lower in smokers and in those with pleural thickening at comparable profusion scores, and these was no difference in FVC between scores 0/1 and 1/0. CONCLUSION: The decrease in FVC with increasing profusion score in both workforces as well as the similar slopes for the relation between FVG and profusion score and the similar FVG at similar scores in the absence of pleural thickening confirm the ILO profusion score as an acceptable assessment of pulmonary fibrosis.     

Lung function and chest radiograph abnormalities among construction insulators.

We carried out a prevalence survey of pulmonary health parameters among current and retired construction insulators (50 years old and older) from all areas of British Columbia, Canada. The study population included 59 active workers (81 percent participation in this group) and 29 workers who were retired or inactive due to illness (69% participation). Radiograph results were compared to those from actively working bus mechanics from the same age group, and retired grain and civic workers, who were all tested in the same manner. Chest radiographs were read independently by two readers and were graded according to the ILO classification system. Pleural abnormalities alone were found in 34% (20) of active workers (5% in comparison group) and 45% (13) of non-active workers (14% in comparison group). Rates for parenchymal abnormalities for these same groups (ILO grade 1/0 or higher) were 17% (5%) and 20% (5%), respectively. Airflow obstruction was present in 35% (31) of the insulators and was associated with age and the presence of diffuse pleural thickening, and 5 or more years of employment in pulp mills. Restrictive lung function was present in 22% (19) of the insulator population and was associated with age and radiographic evidence of parenchymal fibrosis. The results indicate that construction insulators, a group at high risk for asbestos-related lung disease, also have a high prevalence of airflow obstruction. This was associated not only with smoking, but also with diffuse pleural thickening and a history of pulp-mill employment, suggesting that airflow obstruction in this population is also partly work related.     

Radiographic abnormalities in asbestos insulators: effects of duration from onset of exposure and smoking. Relationships of dyspnea with parenchymal and pleural fibrosis

Chest radiographs and spirometry were evaluated in 2,907 active and retired asbestos insulators; most (86.8%) had greater than or equal to 30 years from onset of asbestos exposure. Testing was performed in 19 cities in the United States during 1981-1983. Complete demographic, smoking, clinical, and radiologic data were obtained for 2,790 workers. This is the largest single group of insulators that has been studied. Five hundred forty-eight (19.7%) had never smoked cigarettes, 942 (33.9%) were current cigarette smokers, and 1,300 (46.6%) were ex-smokers. Only 439 (15.7%) workers had no radiographic evidence of asbestos-related disease (normal chest X-ray); 668 (23.9%) had pleural fibrosis only, 325 (11.6%) had parenchymal fibrosis alone, and 1,358 (48.7%) had both parenchymal and pleural fibrosis. The prevalence of radiographic parenchymal changes increased significantly (p less than .001) from 38.6% (DURONSET less than 30 years) to 70% (greater than or equal to 40 years). For pleural changes the comparative prevalences were 55% and 82%. Those with no history of cigarette smoking were more likely to have normal films than those with a history of smoking (19.2% versus 14.4% for current smokers and 15.2% among ex-smokers), and were less likely to have parenchymal fibrosis (44.5% versus 69.7% for current smokers and 60.2% of ex-smokers). Dyspnea, MRC grade 3 and higher, was more prevalent when pleural fibrosis was associated with interstitial pulmonary fibrosis (at all profusion levels of small opacities) than when pleural fibrosis was absent. Logistic regression analysis of factors contributing to such dyspnea showed that the presence of combined parenchymal and pleural abnormalities was a significant explanatory variable, in addition to age, smoking, and body mass (Quetelet index); the presence of parenchymal changes only or of pleural changes only, as factors contributing to dyspnea, did not reach the level of statistical significance in the regression analysis. The results of these examinations show that pleural fibrosis is a frequent finding in asbestos-exposed groups with long-term follow-up and that its functional significance is not negligible. The contribution of cigarette smoking to prevalence and severity of interstitial fibrosis is an additional reason for smoking cessation among asbestos-exposed individuals.     

Roentgenographic manifestations and pulmonary function effects of asbestos-induced pleural thickening.

Pleural thickening is the most common roentgenographic manifestation of past asbestos exposure. In addition to pleural thickening serving as a specific market of exposure, discrete (plaques) and diffuse pleural fibrosis are important abnormalities because they have been found to be associated with increased risk for other asbestos-related sequelae and to themselves have an adverse effect on pulmonary function. We review here the results of an evaluation of a cohort of asbestos-exposed workers, plumbers and pipefitters, who were consecutively enrolled in a large cross-sectional prevalence study. Among the 681 male participants, pleural abnormalities were associated with decreased values of forced vital capacity, an effect independent of ILO profusion grade. The risk for pleural disease was unexplained by smoking status. Diffuse pleural thickening was more common and was associated with greater decrements in function than was discrete thickening.     

Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers

Eighty-seven workers exposed to asbestos in a railroad car repair shop, with characteristic asbestos-induced pleural plaques, underwent extensive lung-function examination. Vital capacity (VC) showed the greatest reduction among the static lung volumes, with an asymmetrical distribution of one-fourth of the subjects below 80% of the predicted value. Logistic regression demonstrated VC to be sufficient for optimal discrimination of asbestos-exposed subjects from a group of matched controls. No further discriminatory power was gained by additional spirometric measures, lung mechanics, blood gas analysis, or diffusing capacity. Smoking had an influence on dynamic but not on static lung volumes. In conclusion, reduced static lung volumes among smoking asbestos-exposed workers with pleural plaques should, in the absence of other lung diseases, be mainly attributed to the asbestos exposure.     

Pleural plaque profiles on the chest radiographs and CT scans of asbestos-exposed Japanese construction workers

Pleural plaques are asymptomatic focal thickenings of the pleura and considered the hallmark of asbestos exposure. However, it is often difficult to detect pleural plaques on chest x-rays (CXR). In a retrospective study, using chest CT scans of 140 Japanese asbestos-exposed construction workers who have probable or definite findings of pleural plaque on CXR; firstly, we proposed plaque morphology-based classification for CXR findings, and then we examined if those classified findings could be confirmed as pleural plaques on CT scans. Our morphology-based classification of pleural plaque findings included nine types. The percentages of confirmed pleural plaques on CT scans by type (number of confirmed pleural plaque on CT/number of observed on CXR) were 93% (40/43) for straight, 89% (56/63) for diamond, 88% (7/8) for double, 83% (19/23) for tapered medially, 80% (20/25) for parallel, 77% (23/30) for crescent, 79% (11/14) for tenting, 72% (18/25) for tapered-laterally (long type), and 0% (0/9) for tapered-laterally (short type). When added to the ILO classification, morphology-based classification of CXR pleural plaque findings makes its detection easier and hence chest radiograph continues to be a suitable tool for screening asbestos-related pleural plaques based on its simplicity, low radiation exposure, wide availability and cost-effectiveness.     

Chest radiographs in subjects with asbestos-related abnormalities: comparison between ILO categorizations and clinical reading.

The findings of a previous chest X-ray screening, determined without using standardized criteria, were reassessed by means of the ILO classification. Of 470 radiographs that had been determined as showing asbestos-related changes, 430 were categorized according to the ILO Classification. Small opacities with profusion greater than or equal to 1/0 were described in 39 (52%) of 75 participants who, on the original clinical reading, had been determined as having lung fibrosis, and in 45 (12.7%) of 355 who were determined as having pleural changes only. When considering circumscribed pleural thickening at the chest wall or diaphragm, as categorized by the ILO Classification, such changes were present in 401 (93.7%) of 428 subjects with pleural changes as determined on the clinical reading. In addition to the improved sensitivity and specificity achieved, the ILO Classification also allows comparison with other studies. The most apparent disadvantage of the ILO system is that it cannot firmly separate the various types of asbestos-related pleural changes. The study revealed that the previous asbestos exposure of the case subjects had occurred in many different workplaces and occupations.     

Asbestos plaques in a typical veteran's hospital population

Previous authors have described several pleural abnormalities on chest radiography as being pathognomonic for asbestos exposure. We sought to determine the percentage of admissions and outpatients at a typical Veteran's Affairs hospital with these findings, and researched medical records to verify the frequency at which patients having positive radiographs were suspected either by clinical/occupational history or radiologically to have had prior significant exposure to asbestos. Radiographs of 1,212 consecutive patients were evaluated by a certified B reader, and the medical records as well as previous radiology reports of all positive patients were reviewed. Twenty-eight (2.3%) of the radiographs had pleural abnormalities consistent with asbestos exposure, with the patients, all male, ranging in age from 50 to 98 years (mean 75.6). Radiology reports described pleural plaques in only 12 of the 21 (57%) cases with prior exams available; in only seven (33%) was an asbestos etiology considered by the interpreting radiologist. The plaques were misdiagnosed in four instances as being indicative of other, unrelated pathology. A history of known dust exposure was expressed by only five patients (18%). Eleven described working in occupations now known to have a high incidence of exposure, but neither patient nor examining physician expressed consideration of dust inhalation. In conclusion, we have found that a significant percentage of patients in certain subpopulations show radiographic evidence of asbestos exposure that may be a harbinger of related pathology. Unfortunately, because of a low index of suspicion, thorough environmental histories are often deferred, many radiographic changes are either not recognized or are misdiagnosed, and these patients are not followed with the stringent protocols they deserve. © 1996 Wiley-Liss, Inc.     

Railways and asbestos in Japan (1928-1987)--epidemiology of pleural plaques, malignancies and pneumoconioses-

Asbestos has been an indispensable insulating material for railway industries, especially steam locomotives (SLs). This review (1928-1987) consists of three parts. 1) Pleural plaques: Since the 1970s, pleural plaques have been regarded as evidence of past asbestos inhalation, and more recently recognized as a risk factor of asbestos-related malignancies. For diagnostic criteria on plain radiographs, the modified ILO 1980 International Classification of Radiographs of Pneumoconioses was used. Most cases had pleural plaques with normal lungs. Large plant workers showed a significantly higher rate of plaques than workers in smaller plants. Bilateral plaques were dominant followed by the left, then the right lung, and chest wall plaques were dominant over the diaphragm. The manifestation of pleural plaques was more correlated to years since the onset of the asbestos exposure than the sum of asbestos work years, although the result was not significant. The boilermen of railway ferry steamers had a significantly higher plaque rate than other seamen. CT studies on plaques started in 1978. 2) Asbestos-related malignancies: Five retrospective cohort studies 1960-1970 were made on primary lung cancer incidence and mortality among 350,000 active railway men with smoking information. The follow-up period was 20 yr at the longest. Almost all plant workers showed a tendency of higher incidence or mortality than the controls. Two cases of mesothelioma were reported in 1980. 3) Pneumoconioses: Most studies (1928-1975) had relatively low prevalence rates among SL-related workers.     

Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study

The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.     

Development of radiological and clinical evidence of parenchymal fibrosis in men with non-malignant asbestos-related pleural lesions.

After assessment of radiographs taken in 1966, 201 men employed at HM Dockyard, Devonport, were judged to have pleural abnormalities due to exposure to asbestos but to be free from small opacities (ILO U/C 1971 category 1/1 or more), mesothelioma, or bronchial carcinoma. By 1976, 32 of these men had died. Of the survivors, 155 were re-examined to determine the attack rates of parenchymal fibrosis or malignant disease, or both. In 1976, 16 (10.3%) of the survivors had radiographs showing small opacities of category 1/1 or more. When additional clinical criteria had to be satisfied before a diagnosis of parenchymal fibrosis was made the attack rate in the survivors was 4.5%. These attack rates were substantially higher than those observed in a sample of men with no initial pleural abnormality but were unrelated to age, smoking habit, occupation, duration of exposure to asbestos, or type of pleural abnormality. The number of cases of malignant disease was too small to allow any reliable conclusions.     

A new high resolution computed tomography scoring system for pulmonary fibrosis, pleural disease, and emphysema in patients with asbestos related disease.

The aim of this study was to describe a scoring system for high resolution computed tomographic (HRCT) scans analogous to the International Labour Office (ILO) scoring system for plain chest radiographs in patients with asbestos related disease. Interstitial fibrosis, pleural disease, and emphysema were scored, the reproducibility and the interobserver agreement using this scoring system were examined, and the extent of the various types of disease was correlated with measurements of lung function. Sixty asbestos workers (five women and 55 men) mean age 59 (range 34-78) were studied. The lungs were divided into upper, middle, and lower thirds. An HRCT score for the extent of pleural disease and pulmonary disease in each third was recorded in a way analogous to the International Labour Office (ILO) method of scoring pleural and parenchymal disease on chest radiographs. A CT score for the extent of emphysema was also recorded. Pleural disease and interstitial fibrosis on the plain chest radiographs were assessed according to the ILO scoring system. A chest radiographic score for emphysema analogous to that used for HRCT was also recorded. Two independent readers assigned HRCT scores that differed by two categories or less in 96%, 92%, and 85% compared with 90%, 78%, and 79% of cases for chest radiographs for fibrosis, emphysema, and pleural disease respectively. There was better intraobserver repeatability for the HRCT scores than for the chest radiograph scores for all disorders. Multiple regression analysis showed that scores for interstitial fibrosis, emphysema, and pleural disease on chest radiographs and HRCT correlated to a similar degree with impairment of lung function.