The discriminant value of pulmonary function tests in asbestosis

Our plain-English summary of The discriminant value of pulmonary function tests in asbestosis, by M.L. Thomson, A.M. Pelzer, W.J. Smither (Annals of the New York Academy of Sciences, 1965).

The study

• Authors: M.L. Thomson, A.M. Pelzer, W.J. Smither
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):421-36
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002512).

Abstract

A clinical and pulmonary function field survey was made of 28 factory workers who had been exposed to asbestos dust for an average of 14 years. In certifying 19 of these as having asbestosis, the British Pneumoconiosis Board relied mainly on radiological abnormality and the presence of dyspnea and rales, in that order. Finger clubbing came next in importance and cyanosis, productive cough and wheeze were of relatively minor value.

The power of 11 pulmonary function indices to discriminate between the certified and uncertified workers, estimated by the U/Umax test, was greatest for inspiratory capacity (IC), vital capacity (VC), diffusing capacity for carbon monoxide (DCO) and compliance. These indices therefore supported the Board's selection. The discriminant value was lower in forced expiratory volume (FEV) and pulmonary capillary blood volume (Vc), and poor in membrane diffusing capacity (DM), airway conductance (AWC), peak flow rate (PFR), residual volume/total lung capacity (RV/TLC) and FEV/VC.

The influence of the reduced lung volume found in asbestosis on the more specialized tests has been considered, and an attempt made to determine whether they provide significant extra information.

The VC or IC alone correctly classified all but a few individuals. In some certified workers, however, these volumes were normal but the DCO and compliance were low.

Abnormality in the arterial blood oxygen saturation (by ear oximeter) was present in seven workers; it was usually, but not invariably, associated with a low DCO.

Severe obstructive defect was rare in these workers. The mean FEV/VC ratio was within 10 per cent of normal; this small reduction appeared to be due mainly to dynamic factors other than airway obstruction. This was borne out by the airway conductance (by body plethysmograph) and by the PFR, which on the average were better than might have been anticipated in view of the reduction in lung volume. The AWC was low in workers with wheeze and high in the remainder. Of the two simpler indices, PFR correlated more highly with conductance than FEV. Perhaps the main value of the AWC and, to a lesser extent, of the PFR was in excluding airway obstruction in a proportion of workers with asbestosis, and enabling greater precision in its diagnosis and evaluation.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This study examined 28 workers from one asbestos factory who had been exposed to asbestos dust for an average of 14 years. Nineteen had been certified by the British Pneumoconiosis Board as having asbestosis, and nine were exposed but uncertified. The article does not name the fiber type. The Board appeared to rely mainly on X-ray, rales (crackling lung sounds) and breathlessness. Of 11 lung function tests, inspiratory capacity, vital capacity, carbon monoxide diffusing capacity and compliance best separated the two groups. Vital capacity or inspiratory capacity alone correctly classified all but a few workers. Seven of 24 workers tested (six certified, one uncertified) had abnormal blood oxygen saturation. In a second survey, mean forced expiratory volume (FEV) in 16 certified workers was 52 per cent of that in 32 controls. The authors linked most of this to reduced lung volume, and severe airway obstruction was rare. The authors concluded that the lung function tests largely supported the Board's certifications. They noted that the workers formed a continuum rather than separate study and control groups.

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: Cross-sectional clinical and pulmonary function field survey comparing certified and uncertified asbestos workers, with a second survey of breathing tests that included comparison groups
• Who was studied: 28 asbestos workers from one factory in Britain. Nineteen were certified as having asbestosis (Group C, including four females) and nine were exposed but uncertified (Group UC). Mean age and exposure were 52 years and 13.5 years for Group C, and 51 years and 14.2 years for Group UC. A later breathing-test survey covered 16 certified and 6 uncertified workers, compared with 15 workers (described as office workers in the methods and as minimally exposed workers from the same factory in Table 3) and 32 normal subjects.
• Exposure: Asbestos dust in a factory, for an average of 14 years. Fiber type, products and jobs are not specified.
• Main results:
  • X-ray, rales and dyspnea (breathlessness) best distinguished certified from uncertified workers. Overlap between the groups was confined to the lowest severity grade.
  • Of 11 lung function indices, the discriminant index (U/Umax) was greater than 90 per cent for inspiratory capacity, vital capacity, carbon monoxide diffusing capacity and compliance.
  • Vital capacity or inspiratory capacity alone correctly classified all but a few workers. Some certified workers had normal lung volumes but low diffusing capacity and compliance.
  • Many of the indices had poor or negligible power to discriminate asbestosis.
  • Among certified workers, comparing mild and severe grades of X-ray, rales and dyspnea, only the FEV and X-ray combination reached statistical significance (P less than 0.05). The authors noted that one in 20 such comparisons would be significant by chance.
  • Abnormal arterial blood oxygen saturation (below 89 per cent at rest, or a fall of 5 per cent or more on exercise) was found in 7 of 24 workers examined: six certified and one uncertified.
  • Mean FEV was 1.73 litres in the certified group (16 workers), which was 52 per cent of the control group's 3.30 litres (32 subjects).
  • The FEV/VC ratio was similar in the three factory groups (64.4 per cent certified, 60.3 per cent uncertified, 66.3 per cent minimally exposed), compared with 73.35 per cent in controls. The authors concluded that most of the FEV defect was associated with reduced lung volume.
  • On average, airway conductance was within normal limits in all three groups of factory workers.
  • Among certified workers with productive cough, the five with wheeze had a mean specific conductance of 0.13, compared with 0.38 in the remaining eleven without wheeze.
  • Severe obstructive defect was rare in these workers.
• The authors' conclusion: The authors concluded that, on the whole, the lung function evaluation supported the Board's selection of workers for certification, which had been made largely on clinical examination.
• Limitations the authors state:
  • The workers studied formed to some extent a continuum rather than a distinct study group and control group.
  • There is no unequivocal criterion of asbestosis, so certification was used as the yardstick.
  • A truly valid control group could not be found within the factory.
  • Because the ear oximeter was reputed to be inaccurate, minor deviations at rest were not regarded as reliable.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Pulmonary Function Test (PFT), Pneumoconiosis, Dyspnea, Clubbing, Cyanosis, Diffusing Capacity (DLCO), Total Lung Capacity (TLC), Oxygen Saturation.

Related studies

• Pulmonary function in asbestosis: serial tests in a long-term prospective study — M.E. Bader, R.A. Bader, et al. (1965)
• Relationship between chest X-ray findings and pulmonary function tests in dust workers — Y. Tonori, M. Niitsuya, et al. (2005)
• Is it time to end race and ethnicity adjustment for pediatric pulmonary function tests? — A.L. Non, K. Akong, et al. (2024)
• Assessment of progression of asbestosis in the sheep model by bronchoalveolar lavage and pulmonary function tests — R. Bégin, M. Rola-Pleszczynski, et al. (1983)
• The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort — L. Rosenstock, S. Barnhart, et al. (1988)
• Asbestos-induced and smoking-related disease: apportioning pulmonary function deficit by using thin-section CT — S.J. Copley, Y.C. Lee, et al. (2007)

Browse more research in Annals of the New York Academy of Sciences, or return to medical research.