Application of ILO classification to a population without industrial exposure: findings to be differentiated from pneumoconiosis

Radiographic Grading of Extrinsic Allergic Alveolitis

We analyzed the acute phase radiographs of 107 consecutive patients with clinically confirmed extrinsic allergic alveolitis. Three readers independently recorded the profusion and the type of opacities according to the standard ILO criteria extended with categories x, y, z, and ground glass for description as proposed by McLoud et al. (20). The profusion of the changes was grade 0 in 13%, grade 1 in 37%, grade 2 in 35%, and grade 3 in 15% of the interpretations. The type of predominant small opacities was p in 33%, x in 22%, s in 13%, t in 10%, q in 9%, and 0, r, u, y, and z in 13% of the interpretations. Ground glass density was seen in 8% of the recordings. The changes were predominantly located in the middle and lower lung zones. For comparison, according to the classification of Hapke et al. (15), miliary changes (68%) predominated over fibrotic (27%) and normal (11%) recordings. The intraobserver agreement was good by both methods, but there was less interobserver variation with the ILO method. The semiquantitative standardized modified ILO scheme was considered more informative than Hapke's descriptive classification for epidemiologic and research purposes.

Change of exposure response over time and long-term risk of silicosis among a cohort of Chinese pottery workers

An analysis was conducted on a cohort of Chinese pottery workers to estimate the exposure-response relationship between respirable crystalline silica dust exposure and the incidence of radiographically diagnosed silicosis, and to estimate the long-term risk of developing silicosis until the age of 65. The cohort comprised 3,250 employees with a median follow-up duration of around 37 years. Incident cases of silicosis were identified via silicosis registries (Chinese X-ray stage I, similar to International Labor Organisation classification scheme profusion category 1/1). Individual exposure to respirable crystalline silica dust was estimated based on over 100,000 historical dust measurements. The association between dust exposure, incidence and long-time risk of silicosis was quantified by Poisson regression analysis adjusted for age and smoking. The risk of silicosis depended not only on the cumulative respirable crystalline silica dust exposures, but also on the time-dependent respirable crystalline silica dust exposure pattern (long-term average concentration, highest annual concentration ever experienced and time since first exposure). A long-term "excess" risk of silicosis of approximately 1.5/1,000 was estimated among workers with all annual respirable crystalline silica dust concentration estimates less than 0.1 mg/m(3), using the German measurement strategy. This study indicates the importance of proper consideration of exposure information in risk quantification in epidemiological studies.

Previously undetected silicosis in New Jersey decedents

BACKGROUND

Despite a reported decline in mortality and hospitalizations associated with silicosis [U.S. Department of Health and Human Services, 1999], this decline may be artifactual, stemming in part from underdiagnosis by physicians.

METHODS

This study estimates, through radiological confirmation, the prevalence of unrecognized silicosis in a group of silica-exposed New Jersey decedents whose cause of death was chronic obstructive pulmonary disease (COPD), tuberculosis, or cor pulmonale. Two expert readers re-evaluated the chest X-rays of this group to determine the presence or absence of silicosis. The study population was considered to be presumptively exposed to silica dust by virtue of their usual industry of employment as listed on the death certificate.

RESULTS

Radiographic evidence of silicosis was found in 8.5% of this population, and evidence of asbestosis was found in another 10.7%, for a total of 19.2%.

CONCLUSIONS

The existence of previously unrecognized silicosis and asbestosis in 19.2% of this study group suggests that occupational lung disease is under-recognized and, hence, undercounted.

The clinical diagnosis of asbestosis in this century requires more than a chest radiograph

Asbestosis can cause significant impairment and even death. It is also a well-recognized risk factor for the development of lung cancer. However, asbestosis is usually diagnosed on clinical grounds without the aid of pathology. Many physicians and researchers believe that in asbestos-exposed individuals with adequate latency, chest radiographic findings that are compatible with asbestosis are sufficient for the diagnosis. In order to determine whether this approach is reasonable, the positive predictive value of the chest radiograph for the diagnosis of pathologic asbestosis must be determined. This requires information about the prevalence of asbestosis, and the sensitivity and specificity of the chest radiograph in its diagnosis. In this article, the sensitivity and specificity of the chest radiograph in diagnosing asbestosis is determined from a literature analysis. The prevalence of asbestosis among present-day cohorts, such as construction workers and petrochemical workers, is assessed based on the relative risk of lung cancer in patients with asbestosis and the overall relative risk of lung cancer in these occupationally asbestos-exposed cohorts. The results indicate a positive predictive value for abnormal chest radiograph findings alone to be significantly < 50%. Therefore, the chest radiograph is inadequate as the sole clinical tool to be used to diagnose asbestosis in these cohorts. However, when rales and a low diffusing capacity of the lung for carbon monoxide are also present, the diagnosis of asbestosis on clinical grounds can be made with reasonable confidence.

Radiographic evidence of pulmonary fibrosis and possible etiologic factors at a nickel refinery in Norway

Animal studies have shown that nickel compounds may induce pulmonary fibrosis, but so far only limited documentation in humans has been available. Radiographs of 1046 workers in a nickel refinery in Norway were read blindly and independently by three NIOSH certified B-readers, according to the ILO standards. Pulmonary fibrosis (PF) was defined as a median reading of ILO score > or = 1/0 and following this criterion, 47 cases (4.5%) were identified. In logistic regression models, controlling for age and smoking, there was evidence of increased risk of PF with cumulative exposure to soluble nickel or sulfidic nickel (p = 0.04 for both). For metallic nickel a p-value of 0.07 was found. For soluble nickel there was a dose-response trend for 4 categories of cumulated exposure. In the group with the highest cumulative exposure to soluble nickel (low exposure as reference), the crude odds ratio for PF was 4.34 (95% CI 1.75-10.77). The risk adjusted for age, smoking, asbestos and sulfidic nickel was 2.24 (0.82-6.16), with a dose-response trend. The corresponding figures for sulfidic nickel were 5.06 (1.70-15.09, crude) and 2.04 (0.54-7.70, adjusted for age, smoking, asbestos and soluble nickel). However, the dose-response trend was less clear for sulfidic nickel. Controlling for estimated asbestos exposure at the refinery tended to increase the odds ratios of soluble and sulfidic nickel. This study indicates that in addition to age and smoking exposure to soluble and sulfidic nickel compounds are risk factors of PF in humans. Since the number of cases identified in this study is small and undetected confounders may have been present, further studies in other cohorts are appropriate.

International Labor Office Classification System in the age of imaging: relevant or redundant

The 1980 International Labor Office International Classification of Radiographs of Pneumoconioses is a widely used epidemiologic tool with a storied past. This article reviews its development and examines its applications to occupational lung disease and the controversies generated in that process. The question of its relevancy to current imaging practices is discussed.

Reliability and validity of chest radiograph surveillance programs

STUDY OBJECTIVES

Due to the lack of consensus in the literature in the use of posteroanterior (PA) vs PA with right and left oblique views as the optimum radiograph surveillance methodology to investigate pleural changes, a study was undertaken to evaluate the reliability, sensitivity, and specificity of these two approaches.

DESIGN

Three experienced radiologist B readers used the 1980 International Labor Office classification system for pneumoconiosis to independently read chest radiographs of workers with individual identifiers masked. All radiographs were read first as a PA view only. Unknown to the B readers, each subject's PA was then matched to his or her corresponding right and left oblique views (film triad) and re-read several weeks later.

SETTING AND PARTICIPANTS

The respiratory health of 652 workers exposed to refractory ceramic fiber was assessed as part of cross-sectional and longitudinal surveillance programs.

MEASUREMENTS AND RESULTS

kappa Statistics for interreader and intrareader reliability between the PA view and film triad methods were calculated. Sensitivity, specificity, and positive predictive value were assessed by comparing the initial cross-sectional study to the longitudinal study. The film triad method had considerably higher interreader reliability (kappa = 0.59) compared to the PA-only method (kappa = 0.44). Results from the initial cross-sectional study were then compared to findings evaluated longitudinally. The film triad again was superior, demonstrating a positive predictive value of 73.7% compared to only 47.8% for the PA method.

CONCLUSIONS

It is our recommendation that the film triad method be used in surveillance studies where both parenchymal and pleural changes are anticipated.

Lung health among electricians in Edmonton, Alberta, Canada

Respiratory symptoms, lung function, and radiographic changes among 100 actively employed electricians in Edmonton, Alberta, Canada, with 20 or more years of union membership were compared with those of 100 telephone workers. Posteroanterior chest radiographs were evaluated by two experienced chest physicians, with a third arbitrating films that were disagreed upon. Employment in a number of industrial sectors was compared for time and for time-weighted exposure to dust and fumes. Compared with telephone workers, electricians had more usual cough (odds ratio [OR] = 3.36; 95% confidence interval [CI], 1.36-8.31), usual phlegm (OR = 2.44; 95% CI, 1.01-5.86), chronic phlegm (OR = 2.74; 95% CI, 1.13-6.60), and shortness of breath (OR = 2.26; 95% CI, 1.10-4.67), but no differences in lung function. The prevalence of radiographic changes in both groups was low. The electricians had more radiographic changes, but only for the category "any change" was the difference statistically significant (OR = 5.2; 95% CI, 1.06-23.93). Only two electricians had small irregular opacities. Phlegm, chronic phlegm, and chest tightness were significantly associated with cumulative exposure to fumes in the gas and oil industry and to total industrial construction.

Lung health among plumbers and pipefitters in Edmonton, Alberta

OBJECTIVES

A cross sectional study was undertaken to assess lung health among plumbers and pipefitters. Respiratory symptoms, lung function, and radiographic changes among 99 actively employed plumbers and pipefitters with > or = 20 years of union membership were compared with 100 telephone workers.

METHODS

A respiratory symptom questionnaire was administered, including smoking and occupational histories. Spirometry was conducted according to standard criteria. Posteroanterior chest radiographs were evaluated by two experienced chest physicians, with a third arbitrating disagreed films. Members of the union were categorised as pipefitters (n = 57), plumbers (n = 16), or welders (n = 26), based on longest service, and compared with the telephone workers and internally (between groups). Lung health was also compared with employment in several work sectors common to Alberta for time, and for time weighted by exposure to dust and fumes.

RESULTS

Compared with the telephone workers, plumbers and pipefitters had more cough and phlegm, lower forced vital capacity, and more radiographic changes (20% with any change), including circumscribed (10%) and diffuse pleural thickening (9%). None of the plumbers and pipefitters had small radiographic opacities. Among the three subgroups of workers, plumbers had the highest prevalence of radiographic changes. Both plumbers and pipefitters showed higher odds ratios for cough and phlegm than the welders. No differences between groups were found for lung function. Indicators of lung health were not related to work in any sector.

CONCLUSIONS

Plumbers and pipefitters had increased prevalence of symptoms suggestive of an irritant effect with no evidence of bronchial responsiveness. The chest radiographs showed evidence of asbestos exposure, especially in the plumbers, but at lower levels than previously reported. Health screening programmes for these workers should be considered, although the logistical problems associated with screening in this group would be considerable.

Prevalence of small lung opacities in populations unexposed to dusts. A literature analysis

OBJECTIVES

Despite the wide use of the International Labor Organization (ILO) system for reading chest radiographs, little information is available regarding the prevalence of abnormalities in populations unexposed to dusts. Prevalence studies of radiographic changes consistent with dust inhalation, as classified by the system, would be more meaningful if there were better understanding regarding the extent of abnormalities in unexposed populations.

DESIGN

To determine small opacity prevalence in unexposed populations, a review of articles published since 1970 that used the ILO system to classify radiographs of the unexposed, either as subjects or control subjects, was performed. Criteria for inclusion in this review included ascertainment of the lack of exposure of subjects to occupational dusts, and independent reading of radiographs by at least two readers certified in the ILO system (B readers) or experienced in its use. A total of eight published articles presenting data on nine study populations were included in this study.

RESULTS

The prevalence of small opacities graded 1/0 or greater varied widely, with a range from 0.21 to 11.7%. A meta-analysis of the published data yielded a population prevalence of 5.3% (95% confidence interval [CI] = 2.9 to 7.7%). The prevalence was significantly greater in Europe than in North America (Europe, 11.3%; 95% CI = 10.1 to 12.5%; North America, 1.6%; 95% CI = 0.6 to 2.6%). A subset of the studies contained information on gender that showed greater prevalence of lung opacities in male subjects than female subjects (male subjects, 5.5%; 95% CI = 3.4 to 7.6%; female subjects, 3.5%; 95% CI = 1.3 to 5.8%). Based on estimated age information, the studies were divided into two strata (mean age < 50 years vs > or = 50 years). The age-specific pooled prevalence was higher in the studies with mean age > or = 50 years than studies with mean age < 50 years in both Europe (11.7% vs 9.6%) and North America (2.3% vs 0.6%). Prevalence of lung opacities remained significantly higher in Europe and North America in each age stratum. The large difference in the prevalence between Europe and North America could not be explained on the basis of age, gender, or smoking history, although available age and smoking data are less robust.

CONCLUSIONS

These results indicate that a background level of opacities consistent with the radiographic appearance of pneumoconiosis exists in populations considered to be free of occupational dust exposure. Environmental and unaccounted occupational exposures, as well as reader variability, all may play a role in the determination of small opacity prevalence in these subjects and may explain the large differences between Europe and North America. Thorough ascertainments of occupational and environmental exposures are essential to determine the true significance of opacities in populations who are not exposed to dust.

Prevalence of radiographic small lung opacities and pleural abnormalities in a representative adult population sample

The prevalence of radiographic widespread small lung opacities and pleural abnormalities in the general population was assessed as part of the Mini-Finland Health Survey, which was based on a representative sample of people aged 30 years or over. Full-size chest radiographs of 7,095 persons (89% of the sample) were classified. Two radiologists classified all the radiographs according to the ILO 1980 Classification of Radiographs of Pneumoconioses. Small lung opacities and pleural abnormalities were considerably more prevalent in the older age groups and in men. Small lung opacities on the radiographs and pleural abnormalities were associated with work in industrial occupations, particularly in men. There was a clear association between small lung opacities and pleural abnormalities. The sex differences may be related to occupational factors, particularly dust exposure. The elevated risk of pleural plaques in persons with small lung opacities on the radiographs may indicate a fiber effect.

Chest x ray films from construction workers: International Labour Office (ILO 1980) classification compared with routine readings

The extent of agreement between International Labour Office (ILO) and clinical readings of chest x ray films from construction workers was studied. From a survey of 5898 workers 258 subjects with a profusion of small opacities of > or = 1/1 and a stratified sample of subjects with profusion < 1/1 were selected. Only 41% of the films classified as ILO profusion category > or = 1/1 were clinically recorded as non-normal for the parenchyma. The proportion of films recorded as pneumoconiotic (or possibly so) was especially low for irregular opacities (22%), but increased with the profusion category (both rounded and irregular) as well as with the size of rounded opacities (p 3/11, q 12/25, r 3/4). Only with the profusion category > or = 2/1 were most of the films recorded as pneumoconiotic. The specificity and sensitivity were highest in the geographical areas where a few clinical readers had assessed many films each. The proportion of false negative clinical reports was low for circumscribed pleural thickening of the chest wall (9%) and diaphragmatic pleural thickening (6%). For calcified pleural changes and for the combination of diffuse pleural thickening and obliteration of the costophrenic angle, false negative reports were absent. The present study shows an unsatisfactory sensitivity for clinical compared with ILO readings as a means for screening the parenchyma of workers with a risk of pneumoconiosis.

Asbestos-related chest diseases: plain radiographic findings

In summary, there are a wide range of pulmonary manifestations seen in asbestos-exposed individuals from pleural and parenchymal fibrosis to pleural and parenchymal malignancy. The chest roentgenogram has assumed an important role in the detection and surveillance of asbestos-related pleural and parenchymal changes.

Comparative accuracy of high resolution computed tomography and chest radiography in the diagnosis of chronic diffuse infiltrative lung disease

One hundred individuals who had undergone both high resolution computed tomography (HRCT) and chest radiography were studied to determine the accuracy of each technique in establishing the diagnosis of diffuse lung disease. The group consisted of 86 patients with a diagnosis of a chronic diffuse infiltrative lung disease and 14 normal subjects. Two independent observers assessed the HRCT examinations and chest radiographs and recorded the three most likely diagnoses. Overall a confident diagnosis was reached more often with HRCT (49%) than with chest radiography (41%). The diagnoses were correct in 82% of HRCT examinations and 69% of chest radiographs. Diagnoses made on HRCT, irrespective of the degree of certainty, were accurate more often than diagnoses made on chest radiography (56% and 47% respectively). Of the patients thought to have a normal chest radiograph, 42% had diffuse infiltrative lung disease (DILD). Of the patients thought to be normal on HRCT, 18% had DILD. Conversely, normal subjects were correctly identified as such in 82% of chest radiographs and in 96% of HRCT examinations. This study emphasizes the important role of CT in helping to confirm or refute the presence of abnormality when the chest radiograph is normal or questionably abnormal, and underlines the superior diagnostic accuracy of HRCT compared with conventional chest radiography in DILD.

Exposure to asbestiform minerals and radiographic chest abnormalities in a talc mining region of upstate New York

A radiologist in New York reported a high prevalence of pulmonary fibrosis in St. Lawrence and Jefferson counties. The New York State Department of Health responded by conducting a case history study of radiographic abnormalities found in the lung parenchyma and pleura of residents in Lawrence and Jefferson counties, where tremolitic talc has been mined for many years. During a 1-y period, all radiographs from 6 hospitals in the region were reviewed. A B-reader confirmed that 355 of 9,442 patients who were at least 40 y of age (3.8%) had a relevant abnormality; 60% of them reported occupational exposure to asbestiform minerals, and another 15% had a chest condition or injury that could have accounted for the abnormal radiograph. The results should be interpreted cautiously, but there was no evidence of widespread radiographic abnormalities resulting from ambient dust exposure. The data, however, support earlier studies that indicate that talc miners and millers experience excess parenchymal fibrosis and pleural changes. The data also suggest that individuals in the paper industry and construction trades may be at risk.

Correlation of chest roentgenograms with pulmonary function and bronchoalveolar lavage in interstitial lung disease

We used the ILO classification for occupational lung disease to determine whether there was any correlation between the type and/or severity of pulmonary infiltration on chest roentgenograms and either pulmonary function tests or the types of inflammatory cells present in BAL fluid in patients with interstitial lung disease. Of the 62 patients evaluated (27 with sarcoidosis, 18 with IPF, and 17 with a CV disease and lung involvement), 49 had irregular linear opacities and 13 had normal chest x-rays. There were no significant correlations between the types of cells present in BAL fluid and the various categories of infiltrate or profusion of the infiltrates within each disease group. In patients with sarcoidosis, more extensive infiltration (profusion) was associated with lower FEV, (p less than 0.01). In patients with IPE, linear opacity type, profusion, and the presence or absence of honeycombing were not related to the severity of pulmonary function abnormalities. We conclude that the ILO classification for analysis of chest roentgenograms can be applied to patients with interstitial lung disease not associated with an occupational exposure and that this approach is useful, especially for communication. However, these data provide no information regarding the inflammatory process in the lung and limited information regarding abnormalities in pulmonary function.

High-resolution computed tomography of the lung

High-resolution computed tomography (HRCT) and thin-section CT are techniques that are particularly suited for evaluation of the pulmonary parenchyma. These techniques have been found useful in the assessment of bronchiectasis and solitary pulmonary nodules. HRCT offers promise in evaluation of diffuse and focal pulmonary parenchymal disease. The principles and applications of HRCT of the lung are reviewed.

Factors influencing the reading of small irregular opacities in a radiological survey of asbestos miners in South Africa

A cross-sectional radiological survey of 2,245 men who were employed in South African asbestos mines was conducted in 1976. Since 1976, the lungs of 172 of these men who died have been examined to establish the presence of asbestosis or other pneumoconiosis. The x-ray readings (ILO/UC 1971) were compared with the pathological findings. A high prevalence of false positive readings, particularly for two of the three readers, was found. False negative readings were also very prevalent. Detailed information about asbestos and other mining exposure, smoking habit, age, height, and weight were examined to determine what influence they may have had in inducing false positive findings. Other dust exposure and smoking appeared to be possible factors, whereas age and obesity were probably not. It is suggested that the term "small irregular opacities" requires more precise definition.

Epidemiologic investigation of respiratory effects related to environmental exposure to asbestos inside insulated buildings

The respiratory effects of environmental pollution by asbestos inside university buildings were studied by comparing radiographic, clinical, and functional parameters among three groups of workers with different levels of exposure. Eight hundred and twenty-eight (828) people who worked for at least 15 yr in asbestos-insulated buildings and who were without known occupational exposure to asbestos (environmentally exposed group [EE]) were compared to a group of 252 workers with occupational exposure (occupationally exposed group [OE]), used as positive control; and to a group of 350 people with no known exposure to asbestos (nonexposed group [NE]), within the same university. After adjustment for confounding variables, no differences could be seen between groups EE and NE. Group OE exhibited a higher prevalence of pleural changes and lower lung functions than groups EE and NE.

Asbestos disease in sheet metal workers: II. Radiologic signs of asbestosis among active workers

A review of chest x-rays of 707 currently employed New York metropolitan area sheet metal workers found that 29.3% of the workers with 20 years or more of union membership (a surrogate for years of exposure) had radiologic abnormalities characteristic of parenchymal and/or pleural asbestosis, with 18.6% having abnormalities characteristic of parenchymal asbestosis (International Labor Organization [ILO] classification 1/0 or higher) and 17.4% of pleural asbestosis. The prevalence of abnormalities characteristic of either parenchymal and/or pleural asbestosis in the group as a whole was 16.4%, with 10.9% exhibiting signs of parenchymal asbestosis and 9.2% of pleural asbestosis. There was a strong, statistically significant relationship between years in the trade and the prevalence of radiologic abnormalities. These findings underscore the need for medical surveillance of all asbestos-exposed construction workers, including retirees and workers who have had past exposure but who are no longer exposed.

Relationships between radiographic change, pulmonary function, and bronchoalveolar lavage fluid lymphocytes in farmer's lung disease

Ninety four dairy farmers were investigated by chest radiography, pulmonary function tests, and bronchoalveolar lavage. They were divided into five groups--1: 11 subjects with acute farmer's lung; 2: 25 subjects with previously diagnosed farmer's lung who had stayed on their farm; 3: 15 farmers with previously diagnosed farmer's lung who had left the farm; 4: 23 precipitin positive symptomless farmers; 5: 20 precipitin negative symptomless farmers. The study evaluated the relationships between radiographic changes measured with a scoring system derived from the International Labour Office (ILO) classification, the results of pulmonary function tests, and bronchoalveolar lavage fluid. Thirty eight subjects had radiographic evidence of interstitial pulmonary infiltrates. Group 1 had the highest percentage of lymphocytes recovered by bronchoalveolar lavage (mean 66.3 (SD 19.2]. For all subjects carbon monoxide transfer factor (TLCO) and total lung capacity were negatively correlated with radiographic changes (r = -0.45 and -0.30; p less than 0.001 and less than 0.01 respectively). TLCO was also negatively correlated with radiographic change in group 2 (r = -0.59, p less than 0.005). The percentage of lavage lymphocytes was correlated with radiographic changes for all subjects (r = 0.36, p less than 0.001), but this correlation was not seen within groups. This study shows good correlation between radiographic abnormalities, pulmonary function changes and the cellular composition of bronchoalveolar lavage fluid.

Parietal pleural plaques, asbestos bodies, and neoplasia. A clinical, pathologic, and roentgenographic correlation of 25 consecutive cases

An investigation was made to correlate autopsy and roentgenographic findings of pleural plaques with occupational exposure to asbestos and occurrence of respiratory tract tumors. Of the 434 autopsies performed over a 2 1/2 year period, 25 (5.8 percent) had pleural plaques but no gross evidence of parenchymal fibrosis. Review of the posterior-anterior chest roentgenograms using the International Labor Office criteria for classification of pneumoconiosis (1980) revealed that only seven of the 25 cases had detectable pleural thickening or calcification, which demonstrates the poor sensitivity of standard x-ray films. There was no detectable difference in frequency of known or presumed exposure to asbestos between the pleural plaque cases and controls as determined by occupational information obtained from chart review. Asbestos bodies were identified in lung tissue digests from all 25 cases with pleural plaques, and exceeded the normal range for our laboratory in 14 cases (56 percent). Of the 25 cases with pleural plaques, four also had bronchogenic and three had laryngeal carcinoma. The prevalence of bronchogenic carcinoma in patients with plaques was not different from those without plaques (p greater than 0.50). However, the association between plaques and laryngeal carcinoma was highly significant (p = 0.004).