CT Study Reveals Persistent Lung Abnormalities Two Years After COVID-19

In a new study looking at serial follow-up computed tomography (CT) imaging in patients who had COVID-19, researchers noted gradual decreases in the incidence of interstitial lung abnormalities (ILAs) and found the majority of patients had complete radiological resolution at two years. However, the study findings also revealed that 39 percent of patients had ILAs linked to a greater than twofold higher incidence of respiratory symptoms and abnormal diffusing capacity of the lung for carbon monoxide (DLco).

For the prospective study, recently published in Radiology, researchers evaluated 144 patients (median age of 60) during a two-year period after they had recovered from COVID-19. The study authors reviewed results from pulmonary function tests as well as high-resolution chest CT scans obtained at six months, one year and two years after the onset of symptoms for COVID-19. According to the study, 78 percent of the cohort had suffered severe COVID-19 and six patients (4.2 percent) were in critical condition.

Researchers found that 61 percent of the study participants (88/144) had complete radiological resolution at two years and 39 percent of the cohort (56/144) had ILAs. Study participants with ILAs had a 19 percent higher frequency of respiratory symptoms (including exertional dyspnea and cough) and a 23 percent higher frequency of lung diffusion abnormalities (DLco < 75 percent of the predicted value) on pulmonary function testing in comparison to those who had radiological resolution, according to the study findings.

The study authors also found that study participants with fibrotic ILAs had a 28 percent higher incidence of residual symptoms (45 percent) and a 38 percent lower DLco (60 percent) in comparison to those with non-fibrotic ILAs (17 percent and 22 percent, respectively).

“It may be possible that persisting residual symptoms and abnormal lung function, or further deterioration, is related to the patient’s ongoing parenchymal lung damage. Participants with ILAs had symptoms or dysfunction that might represent mild interstitial lung disease,” wrote study co-author Heshui Shi, M.D., Ph.D., who is affiliated with the Department of Radiology at Union Hospital and Tongji Medical College at the Huazhong University of Science and Technology in Wuhan, China.

While the researchers did see a gradual reduction in ILA incidence (decreasing from 54 percent at six months to 39 percent at two years), they noted that the proportion of fibrotic ILAs remained consistent at 23 percent throughout the two-year follow-up period.

“ … The fibrotic ILAs observed in our study might represent a stable, irreversible pulmonary sequelae, such as lung fibrosis, after COVID-19,” suggested Shi and colleagues.

(Editor’s note: For related content, see “COVID-19 and Cancer: What a New Chest CT Study Reveals” and “Study Shows Merits of Photon-Counting CT in Detecting Subtle Post-COVID Lung Abnormalities.”)

The study authors noted that ground-glass opacities (GGOs) and reticular abnormalities were among the CT findings for non-fibrotic ILAs. However, Shi and colleagues also maintained that post-COVID 19 CT findings of subpleural GGOs and reticular abnormalities could reflect fine interstitial fibrosis.

In an accompanying editorial, Edwin J.R. van Beek, M.D., Ph.D., FRCR, emphasized the importance of distinguishing between fibrotic and non-fibrotic ILA on CT.

“Once distortion and traction bronchiectasis and bronchiolectasis are present, the findings will likely become irreversible, as noted by (the study authors). It is therefore important during follow-up examinations in clinical practice to recognize this difference, as patients with non-fibrotic ILA findings are more likely to still recover, even as late as 2 years after the initial infection episode,” noted Dr. van Beek, the Scottish Imaging Network (SINAPSE) chair of clinical radiology at the University of Edinburgh in Scotland.

In addition to the limitations of a single-center study, the researchers noted the study cohort was only infected with the alpha strain of COVID-19, which may limit extrapolation of the study findings to patients with other COVID-19 variants. The study authors also suggested the prevalence of long COVID-19 may have been overestimated due to the study’s exclusion of patients with preexisting lung disease and those who had a normal CT upon hospital discharge.