China: A recent study found interstitial lung abnormalities to be persistent even after 1 one year (as seen on CT scans) in severe COVID-19 survivors. This correlated negatively with the lung diffusion capacity.The study has been published in the journal Radiology.
Lung sequelae post-COVID-19 is a major concern to all populations given the large scale of the COVID-19 pandemic worldwide. Previous studies have shown one-third of severe COVID-19 survivors to have lung "fibrotic-like" changes [fibrotic interstitial lung abnormalities (ILAs) according to Fleischner Society Glossary] on 6 months follow up. However, whether these fibrotic ILAs changes are permanent, progressive or reversible is not clear and not much is known about the one-year sequela of COVID-19.
Heshui Shi, Department of Radiology, Wuhan Jinyintan hospital, People's Republic of China, and colleagues aimed to assess the chest CT changes of fibrotic ILAs at one-year follow-up in COVID-19 survivors in a prospective study.
The study included a total of 71 participants who harbored lung sequelae (40 cases with fibrotic ILAs [previously described as fibrotic-like changes], 31 cases without fibrotic ILAs, including ground-glass opacification (GGO), consolidation or reticular abnormalities) at six-month follow up in a previous study were invited to a one-year follow-up study.
After exclusion, 62 participants (34 men, 28 women; mean age, 57±10 years; 35 cases with fibrotic ILAs, 27 cases without fibrotic ILAs) were prospectively enrolled in this study. Six-month and one-year follow-up CT scans were obtained on 182 days and 363 days after symptoms onset, respectively.
The researchers used WHO's interim guidance diagnostic criteria for adults with severe COVID-19 pneumonia. Within 1 week of the follow-up CT scans, 57 participants underwent standard pulmonary function testing (PFT) at six months while 53 participants had PFT tests at one year. The severity of the diffusing lung capacity drop was assessed using a standardized grading system (4): Normal, >75% - 140%; mild, 60% - 75%; moderate, 40% - 59%; and severe, <40%.
Using the same scanners as the 6-month CT scans, all 62 participants underwent one-year follow-up CT examinations. CT images obtained at 6-month and one year were reviewed side-by-side in random order by three senior cardiothoracic radiologists. After independent evaluation, discussion and consensus resolved any disagreement. For each patient, CT features according to the Fleischner Society glossary were assessed and recorded.
A semiquantitative CT score was used to quantify the extent of pulmonary abnormalities (all lesions, GGO, consolidation, interstitial lung abnormalities, and fibrotic interstitial lung abnormalities and traction bronchiectasis).
Key findings of the study include:
In group 1, all participants (100%) demonstrated persistent fibrotic ILAs on one-year follow-up CT scans.
Specifically, 77% participants had stable lung fibrotic ILAs while the extent of fibrotic ILAs was slightly reduced in 23% cases.
63% of participants in group 2 showed complete resolution on one-year CT, while the remaining 37% participants showed either partial resorption of the abnormalities (22%), or static radiologic changes (15%).
Compared with the 6-month CT scans, decrease in the CT scores of all lesions, GGO, reticular pattern and ILAs were observed on one-year CT scans.
CT scores of the fibrotic ILAs and traction bronchiectasis showed no differences between the two CT scans.
Regarding PFT findings, DLCO% abnormality was mostly and consistently mild, with no severe grading.
Although the DLCO% value slightly improved over time (85±12% vs 89±19%), no differences were found between the two occasions PFT and the severity of DLCO%.
At the one-year follow up, 15% participants suffered from exertional dyspnea, of which, 78% participants had fibrotic ILAs on CT.
There were still 25% participants with abnormal pulmonary diffusion on one-year PFT seen particularly in those with fibrotic ILAs (85%).
A negative correlation was found between the score of fibrotic ILAs and DLCO% at one year follow up.
"We conclude that interstitial lung abnormalities were found to be persistent at one-year follow-up CT scans in severe COVID-19 survivors, which were correlated with a reduction in the diffusion capacity of carbon monoxide," wrote the authors. "These findings need to be confirmed by further investigations on larger population."
Reference:
The study titled, "Fibrotic Interstitial Lung Abnormalities at 1-year Follow-up CT after Severe COVID-19," is published in the journal Radiology.
DOI: https://pubs.rsna.org/doi/10.1148/radiol.2021210972