In a study recently published online in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine, researchers sought to ascertain the incidence of residual lung abnormalities in individuals hospitalized with COVID-19 based on risk strata.

The United Kingdom Interstitial Lung Disease (UKILD) study was conducted in cooperation with the PHOSP (posthospitalization)-COVID study, which consists of researchers and clinicians from across the UK designed to explore how different patients who were hospitalized with COVID-19 subsequently recovered. The UKILD COVID study excluded patients in PHOSP-COVID who had interstitial lung disease (ILD) prior to COVID-related hospital admission.

Interim study participants were discharged from the hospital by the end of March 2021, while interim data were collected until October 2021, restricting the analysis to 240 days after discharge. The researchers identified patients with thoracic CTs from the PHOSP-COVID database.

The primary outcome was to confirm the prevalence of residual lung abnormalities in individuals discharged from a COVID-19 hospitalization. Analyses were performed to establish participants’ risk factors of residual lung abnormalities in those who did not receive a CT scan. These risks were utilized to estimate prevalence in the overall population hospitalized by the end of March 2021.

A total of 3,700 individuals were included in the interim cohort. Results revealed that out of 209 subjects with related CTs (average 119 days, interquartile range 83-155), 166 individuals (79.4%) had >10% involvement of residual lung abnormalities.

Risk factors included abnormal chest x-ray (relative risk [RR] 1.21; 95% credible interval [CrI], 1.05-1.40), percent predicted diffusing capacity of the lungs for carbon monoxide <80% (RR 1.25; 95% CrI, 1.00-1.56), and severe admission requiring ventilation support (RR 1.27; 95% CrI, 1.07-1.55). Moderate to very high risk of residual lung abnormalities was classified in 7% to 8% of the remaining 3,491 individuals and posthospitalization prevalence was estimated at 8.5% (95% CrI, 7.6%-9.5%), increasing to 11.7% (95% CrI, 10.3%-13.1%) in sensitivity analysis.

The authors concluded that their findings emphasize the significance of radiological and physiological monitoring of patients at both early and later follow up. Findings also indicated that residual lung abnormalities were estimated in up to 11% of individuals discharged following COVID-19-related hospitalization and health services should monitor at-risk individuals to understand long-term functional implications. The authors also noted that more research is warranted to gain more insight in the progressive development of radiological patterning or resolution over time.

The authors wrote, “The UKILD Post-COVID interim analysis of residual lung abnormalities in patients hospitalized for COVID-19 offers the largest assessment of prevalence in hospitalized individuals to date and is consistent with findings from a number of smaller studies that demonstrate persistent radiological patterns and impaired gas transfer during the extended follow up of patients with COVID-19. At the time of this interim analysis, it is not possible to determine whether the observed residual lung abnormalities represent early interstitial lung disease with potential for progression, or whether they reflect pneumonitis that may be stable or resolve over time.”

In a press release on the American Thoracic Society website, the researchers also stated, “The next phase of the study is a primary analysis, which will be performed at 12 months. At that time, we will also use linked electronic health records of hospital admissions and mortality data to support our analyses. We expect to have the final results in early 2023.”

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