Systematic review of pleural plaques and lung function

Abstract

Context: US EPA proposed a Reference Concentration for Libby amphibole asbestos based on the premise that pleural plaques are adverse and cause lung function deficits.

Objective: We conducted a systematic review to evaluate whether there is an association between pleural plaques and lung function and ascertain whether results were dependent on the method used to identify plaques.

Methods: Using the PubMed database, we identified studies that evaluated pleural plaques and lung function. We assessed each study for quality, then integrated evidence and assessed associations based on the Bradford Hill guidelines. We also compared the results of HRCT studies to those of X-ray studies.

Results: We identified 16 HRCT and 36 X-ray studies. We rated six HRCT and 16 X-ray studies as higher quality based on a risk-of-bias analysis. Half of the higher quality studies reported small but statistically significant mean lung function decrements associated with plaques. None of the differences were clinically significant. Many studies had limitations, such as inappropriate controls and/or insufficient adjustment for confounders. There was little consistency in the direction of effect for the most commonly reported measurements. X-ray results were more variable than HRCT results. Pleural plaques were not associated with changes in lung function over time in longitudinal studies.

Conclusion: The weight of evidence indicates that pleural plaques do not impact lung function. Observed associations are most likely due to unidentified abnormalities or other factors.

Keywords: Asbestos; FEV; FVC; X-ray; high-resolution computed tomography; lung function; pleural plaques.

Figure 1.

Literature identification and screening process.

Figure 2.

Risk of bias evaluation process.

Figure 3

Spirometry results in high quality HRCT and X-ray studies. Percent predicted FVC and FEV₁, and FVC/FEV₁ ratio, among individuals with no lung lesions (light gray bars) or pleural plaques (dark gray bars). Error bars indicate standard deviations, except for Hilt et al. (1987), where no standard deviations were reported. (A, B and C) show the results of higher quality HRCT studies and (D, E and F) show the results of the higher quality X-ray studies.