Diagnostic performance of radiologists in distinguishing post-COVID-19 residual abnormalities from interstitial lung abnormalities

Abstract

Objective: Distinguishing post-COVID-19 residual abnormalities from interstitial lung abnormalities (ILA) on CT can be challenging if clinical information is limited. This study aimed to evaluate the diagnostic performance of radiologists in distinguishing post-COVID-19 residual abnormalities from ILA.

Methods: This multi-reader, multi-case study included 60 age- and sex-matched subjects with chest CT scans. There were 40 cases of ILA (20 fibrotic and 20 non-fibrotic) and 20 cases of post-COVID-19 residual abnormalities. Fifteen radiologists from multiple nations with varying levels of experience independently rated suspicion scores on a 5-point scale to distinguish post-COVID-19 residual abnormalities from fibrotic ILA or non-fibrotic ILA. Interobserver agreement was assessed using the weighted κ value, and the scores of individual readers were compared with the consensus of all readers. Receiver operating characteristic curve analysis was conducted to evaluate the diagnostic performance of suspicion scores for distinguishing post-COVID-19 residual abnormalities from ILA and for differentiating post-COVID-19 residual abnormalities from both fibrotic and non-fibrotic ILA.

Results: Radiologists' diagnostic performance for distinguishing post-COVID-19 residual abnormalities from ILA was good (area under the receiver operating characteristic curve (AUC) range, 0.67-0.92; median AUC, 0.85) with moderate agreement (κ = 0.56). The diagnostic performance for distinguishing post-COVID-19 residual abnormalities from non-fibrotic ILA was lower than that from fibrotic ILA (median AUC = 0.89 vs. AUC = 0.80, p = 0.003).

Conclusion: Radiologists demonstrated good diagnostic performance and moderate agreement in distinguishing post-COVID-19 residual abnormalities from ILA, but careful attention is needed to avoid misdiagnosing them as non-fibrotic ILA.

Key points: Question How good are radiologists at differentiating interstitial lung abnormalities (ILA) from changes related to COVID-19 infection? Findings Radiologists had a median AUC of 0.85 in distinguishing post-COVID-19 abnormalities from ILA with moderate agreement (κ = 0.56). Clinical relevance Radiologists showed good diagnostic performance and moderate agreement in distinguishing post-COVID-19 residual abnormalities from ILA; nonetheless, caution is needed in distinguishing residual abnormalities from non-fibrotic ILA.

Keywords: COVID-19; Diagnostic imaging; Lung diseases, Interstitial; Tomography, X-ray computed.

Fig. 1

Flow diagram of the study

Fig. 2

a Representative case of post-COVID-19 residual abnormalities. Unenhanced HRCT images show extensive GGO as the predominant finding, with a peribronchovascular distribution. Perilobular opacities (red squares) and parenchymal bands (arrows) are also present. b Representative case of non-fibrotic ILA. HRCT images show GGO as the predominant finding, with a subpleural and basal distribution (red squares). c Representative case of fibrotic ILA. HRCT images show reticulation as the predominant finding, with a subpleural and basal distribution. Traction bronchiolectasis (arrow) and non-emphysematous cysts (arrowheads) are also present

Fig. 3

Receiver operating characteristic (ROC) curves for the classification of post-COVID-19 residual abnormalities and interstitial lung abnormalities (ILA) for each reader. Each curve represents the performance of a different reader, and the legend indicates the area under the curve (AUC) value for each reader’s ROC curve. Higher AUC values indicate better performance in distinguishing between the two conditions. The diagonal gray line represents the chance level, which is the expected performance of a random classifier

Fig. 4

Bar graph showing the distribution of incorrect answers provided by each reader. When the true diagnosis was post-COVID-19 residual abnormalities, the most common incorrect answer given by the readers was “non-fibrotic ILA.” When the true diagnosis was non-fibrotic ILA, the most common incorrect answer was “post-COVID-19 residual abnormalities”