Predictors of pneumonia on routine chest radiographs in patients with COPD: a post hoc analysis of two 1-year randomized controlled trials

Our plain-English summary of Predictors of pneumonia on routine chest radiographs in patients with COPD: a post hoc analysis of two 1-year randomized controlled trials, by D.B. Rubin, H.A. Ahmad, M. O'Neal, et al (International Journal of Chronic Obstructive Pulmonary Disease, 2018).

The study

• Authors: D.B. Rubin, H.A. Ahmad, M. O'Neal, S. Bennett, S. Lettis, D.V. Galkin, C. Crim
• Journal: International Journal of Chronic Obstructive Pulmonary Disease
• Published: 2018;13:189-201
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Patients with COPD are at risk for life-threatening pneumonia. Although anatomical abnormalities in the thorax may predispose to pneumonia, those abnormalities identified on routine chest X-rays (CXRs) in patients with COPD have not been studied to better understand pneumonia risk.

Methods: We conducted a post hoc exploratory analysis of data from two replicate year-long clinical trials assessing the impact of fluticasone furoate-vilanterol versus vilanterol alone on COPD exacerbations (GSK studies: HZC102871/NCT01009463 and HZC102970/NCT01017952). Abnormalities on baseline CXRs from 179 patients who developed pneumonia and 50 randomly selected patients who did not were identified by blinded consensus readings conducted by two radiologists. Positive and negative likelihood ratios and diagnostic odds ratios (ORs) were calculated to evaluate the markers for subsequent pneumonia development during the 1-year study period.

Results: Baseline characteristics distinguishing the pneumonia and non-pneumonia groups included a lower body mass index (24.9 vs 27.5 kg/m2, P=0.008), more severe airflow obstruction (mean post-bronchodilator forced expiratory volume in 1 second [FEV1]/forced vital capacity ratio: 42.3% vs 47.6%, P=0.003), and prior pneumonia (36% vs 20%, P=0.030). Baseline CXR findings with the highest diagnostic ORs were: elevated hemi-diaphragm (OR: 6.87; 95% CI: 0.90, 52.26), thick tracheal-esophageal stripe (OR: 4.39 [0.25, 78.22]), narrow cardiac silhouette (OR: 2.91 [0.85, 9.99]), calcified pleural plaque/mid-chest pleural thickening (OR: 2.82 [0.15, 53.76]), and large/prominent pulmonary artery shadow (OR: 1.94 [0.95, 3.97]). The presence of a narrow cardiac silhouette at baseline was associated with a statistically significant lower mean pre-bronchodilator FEV1 (P=0.040). There was also a trend for a lower mean pre-bronchodilator FEV1 in patients with a large/prominent pulmonary artery shadow at baseline (P=0.095).

Conclusion: Findings on routine CXR that relate to pathophysiological mechanisms of pneumonia could help determine pneumonia risk in patients with COPD.

In plain English

This was a post hoc exploratory analysis of two year-long randomized trials in outpatients with COPD, which compared fluticasone furoate plus vilanterol with vilanterol alone. It was not a study of asbestos exposure, which the article does not report measuring. Of 3,255 randomized patients, 181 developed pneumonia. The baseline chest X-rays of 179 of them were compared with those of 50 randomly selected patients who did not develop pneumonia, and two blinded radiologists read the films together. A calcified pleural plaque over the diaphragm or mid-chest pleural thickening was seen in 5 of 65 pneumonia patients (8%) and in none of 15 non-pneumonia patients with data for this finding. The diagnostic odds ratio was 2.82 (95% CI 0.15 to 53.76, P=0.578). An elevated hemi-diaphragm was seen in 12% of the pneumonia group versus 2% of the comparison group (odds ratio 6.87, 95% CI 0.90 to 52.26). The authors noted that the confidence intervals for these odds ratios all included 1, and that the pneumonia occurred on the same side as the plaque or thickening in only 2 of 9 cases. The authors concluded that these findings may be associated with later pneumonia, and they described the study as hypothesis generating.

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: Post hoc exploratory analysis of baseline chest X-rays from two replicate 1-year randomized controlled trials, comparing patients who developed pneumonia with a random sample of patients who did not
• Who was studied: Outpatients with COPD aged 40 or older with a smoking history of at least 10 pack-years, enrolled in two multicenter trials. Of 3,255 randomized patients, 181 developed pneumonia. The analysis included 179 pneumonia patients with a baseline X-ray and 50 randomly selected patients without pneumonia, 229 X-rays in total.
• Exposure: The factors examined were 21 categories of baseline chest X-ray findings, including calcified pleural plaque over the diaphragm or mid-chest pleural thickening, plus baseline characteristics. Patients received fluticasone furoate (50, 100 or 200 µg) plus vilanterol 25 µg, or vilanterol 25 µg alone. Asbestos exposure was not reported.
• Main results:
  • Calcified pleural plaque over the diaphragm or mid-chest pleural thickening: 5 of 65 pneumonia patients (8%) versus 0 of 15 non-pneumonia patients with data. P=0.578; diagnostic odds ratio 2.82 (95% CI 0.15, 53.76).
  • Data on the pleural plaque/thickening finding were missing for 114 patients in the pneumonia group and 35 in the non-pneumonia group.
  • Elevated hemi-diaphragm: 12% of the pneumonia group versus 2% of the non-pneumonia group. P=0.033; diagnostic odds ratio 6.87 (95% CI 0.90, 52.26).
  • Elevation of the right hilum, a sign of upper lobe volume loss, was less common in the pneumonia group: 11% versus 22%. P=0.048; odds ratio 0.45 (95% CI 0.20, 1.01).
  • For the X-ray findings linked to later pneumonia, the 95% confidence intervals of the diagnostic odds ratios included 1 in every case.
  • Pneumonia occurred on the same side of the chest as the calcified pleural plaque or mid-chest pleural thickening in 2 of 9 cases, and on the same side as an elevated hemi-diaphragm in 10 of 20 cases.
  • Compared with the non-pneumonia group, the pneumonia group had a lower mean BMI (24.9 vs 27.5 kg/m2, P=0.008), a lower post-bronchodilator FEV1/FVC ratio (42.3% vs 47.6%, P=0.003), and more prior pneumonia (36% vs 20%, P=0.030).
• The authors' conclusion: The authors concluded that an elevated hemi-diaphragm, thick tracheal-esophageal stripe, narrow cardiac silhouette, calcified pleural plaque/mid-chest pleural thickening, or large/prominent pulmonary artery shadow on routine chest X-ray may be associated with later pneumonia in patients with COPD. They said these results need confirmation in a prospective or larger study.
• Limitations the authors state:
  • The study was a post hoc retrospective analysis of two previously published trials.
  • Because of the small sample, the analysis was not adjusted for baseline factors, including inhaled corticosteroid use.
  • The comparison group was small, and its members may not be true negatives.
  • The ratio of pneumonia to non-pneumonia patients does not reflect real-world prevalence.
  • Time at risk was not matched between cases and controls.
  • X-ray findings at baseline may have differed from those present when pneumonia was diagnosed.
  • The X-rays came from various machines and sites without standardization, and the readings were subjective with no severity scale.
  • Because many findings were examined, some could be due to chance, so the study is hypothesis generating, not confirmatory.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, COPD, Thorax, Clinical Trial, Odds Ratio, Obstructive Lung Disease, FEV1, Diaphragm.

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