CT in coronavirus disease 2019 (COVID-19): a systematic review of chest CT findings in 4410 adult patients
Main result
- 3272 original articles identified, of which 357 justified full-text reading. Of those, 45 articles (case series only) were selected for the study, totaling 4733 scans and 4410 patients.
- Most frequent "severe" CT signs (% relative to the number of thoracic scanners - the number of scanners taken into account varying according to the signs): frosted glass opacities (50.2%; 2383/4738), mixed lesions: frosted glass opacities and condensations (44.4%; 854/1922), condensations (24.2%; 1021/4221).
- "Appended" CT signs: enlargement of pulmonary vascularization (64%; 353/550), intralobular septal thickening (60%; 310/2053), adjacent pleural thickening (41.7%; 213/511), aerial bronchograms (41.2% ; 572/1388), subpleural lines (25%; 98/388), crazy paving aspect (19.5%; 266/1364), bronchial distortions (18.6%; 21/113), bronchiectasis (18%; 69/385), interlobular septal thickening [excluding crazy paving] (15.1%; 310/2053).
- Lesion location and distribution: bilateral opacities 84% (1185/1407), peripheral or subpleural 68.8% (570/828), posterior 77.7% (178/229)
- Follow up studies (2 studies):
1- Wang et al. (n=90): Frosted glass opacities alone initially (65% on D0-J5), with gradual progression to frosted glass opacities + condensation (38% at week 3), return to frosted glass opacities alone at week 4 (70%); maximum extension at D6-J11.
2- Pan et al. (n=21): frosted glass opacities alone initially (75% at D0-D4), progression to "crazy paving" at D5-D8 (53%), then predominant condensations (91% on D9-D13) resolving progressively after week 2, with a peak at D10.
- Lesion based on clinical severity (2 studies):
1- Liu et al. (n=73): typical COVID-19 lesions: peripheral frosted glass opacities with or without interlobular thickening. Severe COVID-19 lesions: extended frosted glass opacities and condensations. Critical COVID-19 lesions: "white" lung with atelectasis and pleural effusion.
2- Xu et al. (n=50): severe and critical patients (n=13): more frequent multilobar (4-5) and bilateral involvement compared to mildy affected patients .
- Lesions according to age (2 studies): 1- Song et al. (n=51): more extensive lesions and condensation among patients >50 years 2- Zhu et al. (n=72): significantly more extensive multilobar involvement among patients >60 years (71.4% vs. 36.4%, p = 0.009).
Takeaways
The most commonly observed CT lesions in COVID-19 patients are primarily frosted glass opacities, that may further be associated with condensation.
Lesions are mostly bilateral and peripheral. They appear more frequently expanded and multilobar in patients > 50-60 years of age or exhibiting severe form of the disease.
Strength of evidence Weak
Literature review to be considered with caution!
Strengths:
- Systematic review (English only) of the literature.
- Significant study and patient number.
Weaknesses:
- Probable exclusion of a significant number of Chinese articles not written in English.
- Selected articles are case series only, without control group.
- Selected articles might show biased classification of lesions due to the subjectivity of interpretation and description of some radiological signs.
- Some radiological signs seem picked from a limited number of studies. The signs are expressed in % number of scanners performed, which might be misleading (since based on a fraction of the total number of scanners included).
- Probable strong heterogeneity between selected studies (not evaluated by the authors).
- No results from the study quality assessment.
Objectives
Method
- Systematic review of the literature:
-- published between January 1, 2020 and March 31, 2020, in English only
-- on a population of at least 5 patients with confirmed COVID-19 infection
-- describing the appearance of thoracic scanners in these patients
- using 4 databases: PubMed, Embase, Google Scholar, and World Health Organization Library
- evaluation of the article quality according to the NIH Quality Assessment Tool for Case Serie Studies
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