Chest CT of Lung Injury 1 Year after COVID-19 Pneumonia: The CovILD Study

Abstract

Background The long-term pulmonary sequelae of COVID-19 is not well known. Purpose To characterize patterns and rates of improvement of chest CT abnormalities 1 year after COVID-19 pneumonia. Materials and Methods This was a secondary analysis of a prospective, multicenter observational cohort study conducted from April 29 to August 12, 2020, to assess pulmonary abnormalities at chest CT approximately 2, 3, and 6 months and 1 year after onset of COVID-19 symptoms. Pulmonary findings were graded for each lung lobe using a qualitative CT severity score (CTSS) ranging from 0 (normal) to 25 (all lobes involved). The association of demographic and clinical factors with CT abnormalities after 1 year was assessed with logistic regression. The rate of change of the CTSS at follow-up CT was investigated by using the Friedmann test. Results Of 142 enrolled participants, 91 underwent a 1-year follow-up CT examination and were included in the analysis (mean age, 59 years ± 13 [SD]; 35 women [38%]). In 49 of 91 (54%) participants, CT abnormalities were observed: 31 of 91 (34%) participants showed subtle subpleural reticulation, ground-glass opacities, or both, and 18 of 91 (20%) participants had extensive ground-glass opacities, reticulations, bronchial dilation, microcystic changes, or a combination thereof. At multivariable analysis, age of more than 60 years (odds ratio [OR], 5.8; 95% CI: 1.7, 24; P = .009), critical COVID-19 severity (OR, 29; 95% CI: 4.8, 280; P < .001), and male sex (OR, 8.9; 95% CI: 2.6, 36; P < .001) were associated with persistent CT abnormalities at 1-year follow-up. Reduction of CTSS was observed in participants at subsequent follow-up CT (P < .001); during the study period, 49% (69 of 142) of participants had complete resolution of CT abnormalities. Thirty-one of 49 (63%) participants with CT abnormalities showed no further improvement after 6 months. Conclusion Long-term CT abnormalities were common 1 year after COVID-19 pneumonia. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Leung in this issue.

Graphical abstract

Figure 1:

Study flowchart. Hospitalized patients were consecutively enrolled. Persistent symptoms of participants with outpatient treatment were defined by persistent dyspnea, cough, or impaired performance status. PCR = polymerase chain reaction.

Figure 2:

Unenhanced axial (left) and sagittal (right) chest CT scans corresponding to CT severity score. (A) Score of 1: minimal (subtle ground-glass opacities [GGOs], few findings). Scans show subtle subpleural GGO (arrow) in the right and left lower lobes. (B) Score of 2: low (several GGOs, subtle reticulation). Scans show several subpleural GGOs and superimposed reticulation (arrow) in the right and left lower lobes and the left upper lobe. (C) Score of 3: moderate (multiple GGOs, reticulation, small consolidation). Scans show multiple GGOs in all lobes. (D) Score of 4: marked (extensive GGOs, consolidation, reticulation with distortion). Scans show extensive subpleural GGOs and consolidations (arrow) in the dependent lung. (E) Score of 5: massive (massive findings, parenchymal destructions). Scans show massive consolidations in the dependent lung areas, as well as extensive GGOs in the upper lobes. (Parenchymal destruction includes pneumatocele, cavitation, or abscess formation.)

Figure 3:

Risk of developing persistent CT abnormalities at 1-year follow-up. Odds ratio (OR) significance was determined with the Wald Z test. ORs with 95% CIs are presented in a forest plot. Numbers of complete observations and the reference levels of the explanatory variables are indicated on the y axis. Orange indicates positive correlation, and gray indicates not significant or reference. BMI = body mass index, Ref. = reference. (A) Univariable analysis. Risk factors for developing any lung CT abnormalities at 1-year follow-up were identified with logistic regression. (B) Multivariable analysis. Independent risk factors for lung CT abnormalities were identified with multiparameter logistic regression with backward elimination.

Figure 4:

Serial unenhanced axial chest CT scans in three study participants with previous COVID-19 pneumonia. (A–C) Scans in a 44-year-old man. During acute COVID-19, scan shows extensive bilateral ground-glass opacities (GGOs) and subpleural reticulation (A). At 2-month follow-up, almost complete resolution of GGOs with residual subpleural reticulation in the middle lobe is noted (B). These subpleural reticulations (arrow) persisted up to 1 year after onset (C). (D–F) Scans in a 68-year-old-man. During active infection, scan shows patchy bilateral consolidations, a subpleural arcadelike sign, and pleural effusions (D). At 2-month follow-up, a substantial improvement in organizing pneumonia pattern is seen, with GGO and subpleural reticulation, including arcadelike sign (arrowhead) in the left lower lobe (E). At 1-year follow-up, further improvement is seen, but subtle reticulation and GGO can still be detected (F). (G–I) Scans in a 79-year-old man. During admission to intensive care unit, scan shows bilateral consolidations and small areas of GGO (G). At 2-month follow-up, residual GGO and small subpleural microcystic changes (arrow) are seen (H), and persisted up to 1 year after onset (I).

Figure 5:

Change in CT severity score (CTSS) over time. CTSS kinetic at the consecutive time points was investigated with the Friedman test (grouping by the individual) in the entire cohort and the acute COVID-19 severity subsets. The effect size was determined by using the Kendall W test, and differences between time points were compared by using the paired Wilcoxon test. Plots display individual CTSS value trajectories as thin gray lines, thick colored lines represent medians, and interquartile ranges are presented as colored regions. P values of the Friedman test and the Kendall W statistic are presented in the plot captions. Numbers of individuals with the complete set of consecutive CT scans are shown under the plots.