Post-COVID-19 condition, often referred to as long COVID, affects a significant number of individuals who recover from SARS-CoV-2 infection, particularly those with moderate to severe pneumonia. Persistent respiratory symptoms and chest CT abnormalities are common among these patients. However, the lack of unified terminology and standardised imaging protocols has complicated both clinical management and research efforts. To address these issues, an international panel of thoracic radiologists from three major societies collaborated to develop a multisociety consensus statement. This initiative provides evidence-informed best practices for CT indications, imaging acquisition and reporting of post-COVID-19 residual lung abnormalities.
Clear Criteria for CT Imaging
The consensus identifies three primary recommendations for when chest CT should be performed. Firstly, CT is recommended for patients who experience respiratory symptoms lasting at least two months and persisting three months after COVID-19 infection, without an alternative explanation. This group typically includes those experiencing dyspnoea, which is commonly associated with residual CT abnormalities. Secondly, a follow-up CT may be considered for patients hospitalised with moderate to severe COVID-19 pneumonia, typically within three to six months after discharge. Finally, the frequency and timing of further imaging should be guided by clinical context, including the initial extent of lung damage and changes over time.
The guidelines emphasise that CT findings in such patients often include ground-glass opacities, organising pneumonia, fibrotic-like changes and, in some cases, signs of fibrosis. While most abnormalities tend to regress gradually over 12 to 36 months, persistent scarring may remain. These findings may inform treatment decisions, such as corticosteroid use or pulmonary rehabilitation. Importantly, the panel stresses that universal CT screening of all COVID-19 survivors is not justified, given the high volume of potential patients and the typically non-progressive nature of most abnormalities.
Recommendations for CT Acquisition
The consensus outlines detailed protocols for CT acquisition to optimise diagnostic accuracy while limiting radiation exposure. Thin-section CT (≤1.5 mm) during full inspiration is advised for both initial and follow-up scans. When symptoms suggest air trapping or when pulmonary function deteriorates, expiratory phase imaging should be included. In specific cases, such as bilateral basal abnormalities, prone CT may offer additional diagnostic value.
Radiation dose management is a key concern. The panel recommends consistent use of low-dose protocols (1–3 mSv) in accordance with the ALARA principle, while advising against ultra–low-dose CT (<0.5 mSv) due to reduced sensitivity for subtle abnormalities. In cases of acute respiratory deterioration, standard-dose CT is preferred, and contrast-enhanced CT pulmonary angiography may be warranted to assess for pulmonary embolism or perfusion defects. These advanced protocols should be reserved for experienced centres and only employed when clinically indicated.
Unified Terminology and Reporting Practices
Standardising language in CT reporting is essential to avoid misinterpretation and ensure appropriate patient management. The panel recommends using terms from the Fleischner Society Glossary, such as ground-glass opacities, consolidation, reticulation and bronchial distortion. Importantly, the term “fibrosis” should only be applied when specific features like traction bronchiectasis, honeycombing or architectural distortion with volume loss are persistently present.
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The use of “interstitial lung abnormality” (ILA) is strongly discouraged for describing post-COVID-19 findings, as these abnormalities are typically not incidental and differ in clinical trajectory. Similarly, radiologists are advised to avoid attributing post-COVID-19 residuals to patterns like nonspecific or usual interstitial pneumonia unless there is clear evidence of pre-existing or concurrent fibrosing interstitial lung disease (ILD). Where ILD is suspected, distinguishing between post-infectious abnormalities and pre-existing disease is essential, particularly when prior CT scans are available.
This careful framing is vital, as misclassifying residual post-COVID-19 changes as early ILD may lead to inappropriate clinical decisions. Radiologists are encouraged to contextualise findings and, when describing ILD patterns, clarify their likely origin in the patient’s COVID-19 history unless strong indicators suggest otherwise.
This multisociety consensus represents a collaborative effort to harmonise CT-based assessment of post-COVID-19 residual lung abnormalities. By defining clear criteria for imaging, establishing best practices for CT acquisition and unifying terminology for reporting, the statement supports consistent, evidence-based management of patients with lingering respiratory symptoms after COVID-19. With the continuous need for managing the long-term consequences of the pandemic, such standardisation is critical for effective care delivery and research alignment.
Source: Radiology
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