Dublin, Ireland—While much has been learned about the acute infective process of SARS-CoV-2, the virus behind the COVID-19 pandemic, less is understood about the incidence and seriousness of post-COVID pulmonary pathology, according to a new study.

The report in the Annals of the American Thoracic Society points out that the inflammatory response and coagulopathic state in acute SARS-CoV-2 often promotes pulmonary fibrosis.

Irish researchers and colleagues examined a range of measures of recovery for 153 patients who were followed in an outpatient clinic for a median of 75 days after COVID-19 diagnosis.

“We found that fatigue, ill-health and breathlessness were all common following COVID-19,” said lead author Liam Townsend, MD, of St. James’s Hospital and Trinity College in Dublin. “However, these symptoms appeared to be unrelated to the severity of initial infection or any single measurement at the time of an outpatient appointment.”

For the study, researchers graded infection severity into three groups: 1) not requiring admission; 2) requiring hospital admission, and 3) requiring intensive care.

The 153 participants—nearly half, 48%, requiring hospitalization—underwent chest radiography and 6-minute-walk test (6MWT). Researchers assessed fatigue and subjective return to health and measured of C-reactive protein (CRP), interleukin-6, soluble CD25, and D-dimer. They also investigated the association between initial illness and abnormal chest x-ray, 6MWT distance, and perception of maximal exertion.

Results indicate that persistently abnormal chest x-rays were seen in 4%, lower than expected, but the median 6MWT distance covered was 460 m.

The authors note that reduced distance covered was associated with frailty and length of inpatient stay, with most, 62%, reporting that they didn’t feel they had returned to full health. In fact, 47% met the case definition for fatigue. “Ongoing ill-health and fatigue were associated with increased perception of exertion,” the authors write.

Yet, they report, none of the measures of persistent respiratory disease were associated with initial disease severity, adding, “This study highlights the rates of objective respiratory disease and subjective respiratory symptoms following COVID-19 and the complex multifactorial nature of post-COVID ill-health.”

“We were surprised by our findings. We expected a greater number of abnormal chest x-rays. We also expected the measures of ongoing ill-health and abnormal findings to be related to severity of initial infection, which was not the case,” Dr. Townsend added, suggesting, “These findings have implications for clinical care, in that they demonstrate the importance of following up all patients who were diagnosed with COVID-19, irrespective of severity of initial infection. It is not possible to predict who will have ongoing symptoms.”

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