Lung abnormalities persist after COVID-19 hospitalization even without severe illness

Among patients previously hospitalized with COVID-19, researchers estimated that up to 11% had fibrotic patterning, according to a study published in American Journal of Respiratory and Critical Care Medicine.

The abnormal lung patterns observed in this study — which occurred among a substantial proportion of patients who did not require invasive oxygen therapy — may indicate lung damage characteristic of interstitial lung disease, according to an American Thoracic Society press release.

Iain Stewart

“This study highlights that people with persistent respiratory symptoms after infection should be followed closely for lung function impairments and radiological abnormalities,” Iain Stewart, PhD, advanced research fellow from Margaret Turner Warwick Centre for Fibrosing Lung Disease, National Heart & Lung Institute and Imperial College London, told Healio.

In an interim analysis of the U.K. Interstitial Lung Disease Long-COVID-19 Study, Stewart and colleagues evaluated 209 follow-up thoracic CT scans from previously hospitalized COVID-19 patients (median age, 58 years; 68.4% men; 68.9% white) from the Post-Hospitalization COVID study (PHOSP-COVID) to observe abnormal lung patterns. Researchers then compared what they found from the CT scans to risk factors of 3,491 patients from that study without a CT scan in order to determine the risk for residual lung abnormalities.

Patients included in the study were discharged by March 2021, with data gathered up until 240 days following their discharge.

Researchers scored CTs for percentage of residual lung abnormalities, such as ground glass opacities and reticulations, specifically noting when a patient had more than 10% involvement of the lung.

Patients with CT scans

At a median of 119 days (interquartile range [IQR], 83-155 days) following hospital discharge, researchers observed 166 (79.4%) out of 209 patients with a CT had residual lung abnormalities with greater than 10% involvement.

When visually scoring the CTs, researchers found ground glass opacities impacted a mean 25.5% ± 15.9% of the lung, reticulations impacted a mean of 15.1% ± 11% and residual abnormalities impacted a mean of 40.6% ± 20.8%.

Thirty-three patients underwent a follow-up CT scan a median 161 days later (IQR, 109-187). Researchers observed that 26 out of 28 (92.9%) patients who had residual abnormalities on their original scans had these persist on a follow-up scan. Paired analysis showed an overall change in residual lung abnormalities of –3.62% (95% CI, –6.1 to –1.13; P = .006).

Results of a univariate analysis showed that demographic risk factors for residual lung abnormalities greater than 10% included male sex (RR = 1.42; 95% CI, 1.17-1.77) and age older than 60 years (RR = 1.22; 95% CI, 1.06-1.4).

Clinical factors that heightened the risk for residual lung abnormalities included severe illness on admission that required continuous positive airway pressure, invasive mechanical ventilation or extracorporeal membrane oxygenation, with a relative risk of 1.4 (95% CI, 1.23-1.63); abnormal findings on a chest X-ray, with a relative risk of 1.4 (95% CI, 1.22-1.61); and a percent predicted diffusion capacity across the lung for carbon monoxide (ppDLco) less than 80%, with a relative risk of 1.26 (95% CI, 1.02-1.58).

Patients without CT scans

When evaluating the 3,491 patients without CT scans, researchers assessed their risk for residual lung abnormalities using three significant risk factors identified in the prior analysis: ppDLco less than 80%, abnormal chest X-ray and severe illness on admission.

Researchers divided this cohort into risk groups according to how many indicators they met. Fourteen patients (0.4%) met the thresholds for all three (very high risk), 143 (4.1%) met the thresholds for two (high risk), 116 (3.3%) had either a ppDLco less than 80% or an abnormal chest X-ray (moderate risk), 1,256 (36%) met illness severity alone (low risk) and 1,962 (56.2%) met none of the indicators (very low risk).

When comparing the 273 patients who fell in the very high-risk, high-risk and moderate-risk groups with the 166 patients with more than 10% residual abnormalities on CT, Stewart told Healio that he and his colleagues found something surprising.

“Forty-five percent of people with abnormalities on CT [compared with 44.3% of at-risk patients] had no invasive oxygen therapy during admission,” he said. “The high percentage was a surprise and suggests lung damage may not be restricted to just the most severe COVID-19 hospitalizations.”

Researchers then calculated that 7.8% of patients without CT scans most likely had residual lung abnormalities by combining the risk strata of those in the very high-, high- and moderate-risk groups. During sensitivity analysis, which included patients with planned research follow-up, this percentage increased to 10.4%, according to researchers.

Overall, Bayesian modeling estimated that 11.67% of patients hospitalized due to acute COVID-19 prior to March 2021 had fibrotic patterning present on follow-up.

“A limitation is the potential for background abnormalities prior to infection,” Stewart told Healio. “We excluded people reporting clinical management of interstitial lung disease, but the prevalence of subclinical interstitial lung abnormalities could explain some of our findings.”

Stewart offered several suggestions for future studies on this topic.

“Future studies will need to determine the extent to which lung abnormalities resolve, or progress to fibrotic disease, and assess the risk of lung abnormalities in community COVID-19 patients who were not hospitalized,” Stewart told Healio.

For more information:

Iain Stewart, PhD, can be reached at iain.stewart@imperial.ac.uk.

Reference:

Study reveals extent of residual lung damage after COVID-19 hospitalization. https://www.thoracic.org/about/newsroom/press-releases/journal/2022/lung-damage-after-covid-19-hospitalization.php. Published Dec. 2, 2022. Accessed Dec. 2, 2022.