In this multicenter cohort study, we retrospectively evaluated the radiological findings of 212 patients with COVID-19 and there are several findings: I. The main findings of COVID-19 pneumonia on CT include GGO and consolidation tending to be peripheral in distribution with lower zone predominance. II. The CT score of lung involvement is a marker of clinical severity and correlated with CRP. IV. Most COVID-19 pneumonia gradually resolve in 8 days and a few cases forms fibrosis. V.CXR cannot detect lesions in early stage or exclude COVID-19 pneumonia.
In this cohort, the most common clinical symptom are fever, dry cough which were consistent with our previous reports (15). Lymphocytopenia and increase of CRP were reported to be the most common laboratory findings (16, 17). The normal white blood cell and lymphocyte count and increased CRP were the most prominent laboratory findings in current study and Lymphocytopenia were found in 45.2%( 96/212) patients. Chest CT plays an important role in early detection of lung involvement of infection. Ying et al (9) reported 100% of 42 patients suffer from pneumonia as well as Guan et al(18) showed 76.4% of 840 patients manifested as pneumonia undergoing chest CT on admission. 94.3%(200/212) of patients showed the abnormal opacity on the baseline CT and the median time from symptom onset to the baseline CT were 4 days, suggesting pneumonia can occur in the early stage of COVID-19. For the remaining patients without positive findings on the baseline CT, the second CT after 3 days demonstrated GGO. Thus, 100% of 212 patients with COVID-19 manifested as pneumonia. Notably, the abnormal opacity on the baseline CT scan were found in 30 patients with normal body temperature and 14 asymptomatic patients, suggesting that chest CT scans should be done in high exposure-risk individuals to facilitate early identification of lung involvement.
CXR is widely used to detect pulmonary infection, In Kim et al.’s report on the first case of COVID-19 in Korea (19), they found chest radiography was negative but CT scans performed on the same day showed bilateral, multiple GGOs. And Three of the nine patients (33.3%) had parenchymal abnormalities detected by chest radiography were reported by his team (20). In our study, there were no abnormalities on the initial CXR at admission in 14 patients while their baseline CT showed focal or multifocal GGO. And CXR in 1 patient could not be evaluated due to old tuberculosis. Thus,we believe that the high-risk population can benefit from the early CT scan and CXR is yet insufficient for evaluation of the suspected COVID-19 pneumonia.
Chung et al (8) showed three patients (21%, 3/21) with normal CT scans, 12 (57%) with GGO only, and 6 (29%) with GGO and consolidation in appearance, 15 (71%) patients with two or more lobes involved, and 16 (76%) with bilateral disease. Song et al (21) found pure GGO in 77% patients, GGOs with consolidation in 59% cases, bilateral GGOs in 88% of patients. Similarly, we showed that the most common CT findings of COVID-19 pneumonia in the early stage were focal (36%) or multifocal peripheral GGO (51%) with/without patchy consolidation in a lower lung involvement, however, crazy-paving sign and reticulation were not common. Although some of these findings were similar with SARS-CoV, MERS, H1N1 pneumonia (22–24), cautious attention to high exposure risk and CT findings are helpful for early suspicion of COVID-19 pneumonia and isolation as soon as possible.
CT or radiologic scores of involved lung was reported to be associated with clinical outcomes (14, 25–26). Our modified CT score takes into account the number, size and intensity of lesions, based on the previous method and we found the modified CT score negatively correlated with Lymphocyte count while it positively correlated with C-reactive protein, moreover, the baseline CT scores were higher in severe group than in non-severe group. Regarding the prediction of clinical severity, we found an optimal cutoff value of a CT score of 15 with sensitivity of 70% and specificity of 96.5%. Further study was needed to demonstrate whether this modified CT score predict the lung function and clinical outcomes.
The serial CT scans provided an opportunity to observe the longitudinal lung changes of COVID-19 pneumonia. According to the follow-up CT images, the median time interval to gradually resolved opacity in 52 patients was 8 days. Although the third CT scan of 6 patients showed the features suggestive of lung fibrosis with reticular opacities, architectural distortion and bronchial dilatation.
There are some limitations in our research. First, these patients came from multicenter outside Hubei province, thus they cannot represent real condition in whole country. There are remarkable selection bias because most patients were common type, thus, our study could not comprehensively reflect the difference of clinical and CT findings of patients in mild, common, severe and critical type. Another significant limitation is that, only some of our patients underwent a series of CT scans, there were significant differences in the time interval of CT follow-up and treatment options in each center. Therefore, the characteristics of temporal CT changes and the treatment effect on CT findings cannot be clarified in detail.