Normal Chest Roentgenograms in Chronic Diffuse Infiltrative Lung Disease

Our plain-English summary of Normal Chest Roentgenograms in Chronic Diffuse Infiltrative Lung Disease, by G.R. Epler, T.C. McLoud, E.A. Gaensler, et al (1978).

The study

• Authors: G.R. Epler, T.C. McLoud, E.A. Gaensler, J.P. Mikus, C.B. Carrington
• Published: Reprint from the New England Journal of Medicine 298:934-939 April 27 (1978)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study asked how often chest X-rays look normal in chronic diffuse infiltrative lung disease, a group of disorders that here included asbestosis, other dust diseases, sarcoidosis, allergic alveolitis and interstitial pneumonias. A panel of three lung physicians classified the pre-biopsy X-rays of 458 patients whose disease was confirmed by tissue examination. A chest radiologist then re-read selected films mixed with 25 films of healthy people. Of the 458 patients, 44 (9.6 per cent) had normal films. The share with normal films ranged from none in pulmonary alveolar proteinosis to 38 per cent in allergic alveolitis. Among the 44, 57 per cent had reduced forced vital capacity and 71 per cent an abnormal single-breath diffusing capacity, a test of gas transfer. The authors suggested films can look normal when lesions are too small or few, or mainly affect airways or blood vessels. They concluded that patients with normal X-rays and normal breathing mechanics but impaired gas exchange should have a lung biopsy. They noted the radiologist knew about the project, so the count of normal films may be a minimum.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case series reviewing the X-rays taken just before biopsy in patients with histologically confirmed disease. A panel of three pulmonary clinicians classified the films. A chest radiologist then re-read a set of 134 films that mixed the panel's normal, borderline and abnormal films with films of healthy persons.
• Who was studied: 458 patients with histologically confirmed chronic diffuse infiltrative lung disease, of whom 44 with normal X-rays were studied further. In three of these 44, the lung tissue came from autopsy. 25 films of healthy persons, roughly matched for age, sex and date of X-ray, were used for comparison. The authors were at Boston University School of Medicine, Massachusetts General Hospital, Harvard Medical School and Stanford University School of Medicine. Study dates are not given.
• Exposure: This was not a study of an exposure. The diseases included 'environmental lung disease' categories such as asbestosis, allergic alveolitis, talcosis, graphite, berylliosis, silicosis and toxic gases. Asbestos fiber types and exposure levels were not described.
• Main results:
  • Of the 458 patients, 44 (9.6 per cent) had normal chest X-rays before biopsy.
  • The radiologist read all films of healthy persons as normal. The radiologist agreed with the panel's normal reading in 38 of 44 cases. Of the 61 films the panel had called abnormal, the radiologist read only five as normal and two as borderline.
  • The frequency of normal films varied by diagnosis, from none in pulmonary alveolar proteinosis to 38 per cent in allergic alveolitis.
  • Of the 44 patients with normal films, 22 had their biopsy because of dyspnea (breathlessness) and impaired lung function. The other 22 had it for other reasons, such as thoracotomy for plaques or recurrent pleural effusion, or surgery for recurrent pneumothorax. In three cases the tissue was obtained at autopsy.
  • In the 44 patients with normal films, 64 per cent had dyspnea of Medical Research Council Grade 2 or greater. 33 per cent had bilateral fine rales (crackles), rising to 71 per cent in the interstitial pneumonias.
  • In the 44 patients with normal films, 57 per cent had a reduced forced vital capacity and only 16 per cent had a reduced total lung capacity. 71 per cent had an abnormal single-breath carbon monoxide diffusing capacity and 86 per cent a reduced exercise diffusing capacity. Obstructive impairment was seen in nine of the 44.
  • The pathologist judged the lesions in 20 biopsies too limited or too mild to suggest more than minimal effect on function. These 20 included five cases of asbestosis, and the scanned text prints their mean single-breath diffusing capacity as '81 2' per cent of predicted. In the other 24 patients, whose lesions suggested unequivocal impairment, the mean diffusing capacity was 61.7 per cent of predicted and the mean alveolar-arterial oxygen pressure difference was 33.6 torr.
• The authors' conclusion: The authors gave three possible reasons why films may be normal: isolated lesions are too small or too few, diffuse disease may cast no discrete shadows, or lesions mainly affect airways or blood vessels. They concluded that patients with normal X-rays and normal mechanics of breathing but impaired gas exchange should have a lung biopsy for early diagnosis and therapy. In their diagnostic plan, airflow obstruction is excluded first, and a single-breath diffusing capacity below 50 per cent of predicted calls for biopsy. Less severe reductions call for further testing to decide whether a biopsy is needed.
• Limitations the authors state:
  • The radiologist was aware of the project and probably examined the films with special care.
  • Possible over-reading means the number of normal films may be a minimum rather than a maximum.
  • The panel knew the patients had presumably been referred for respiratory complaints.
  • Sampling error: the surgeon may resect a small area that is more severely affected than the rest of the lung.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Interstitial, Biopsy, Diffusing Capacity (DLCO).

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