CT Imaging May Help Distinguish COVID-19 From Interstitial Lung Disease

By Marilynn Larkin

August 13, 2021

NEW YORK (Reuters Health) - Computed tomography (CT) could be used to help distinguish COVID-19 from systemic sclerosis-related interstitial lung disease (SSc-ILD), researchers suggest.

"We found that the ground glass opacities (GGO) in COVID are remarkably different from those in SSc," Dr. Marco Matucci-Cerinic of the University of Florence told Reuters Health by email. "In SSc, the GGO is characterized by signs of fibrosis that are not found in the COVID GGO."

As reported in Rheumatology, Dr. Matucci-Cerinic and colleagues studied CT scans of 99 patients, 52 with COVID-19 and 47 with SSc-ILD. The mean age overall was about 61; about 42% were women.

Twenty-two international CT scan readers were divided into radiologist (RAD) or non-radiologist (nRAD) groups.

CT features most frequently associated with SSc-ILD were fibrosis inside focal GGO in the upper lobes; fibrosis in the lower lobe GGO; and reticulations in lower lobes, especially if bilateral and symmetrical or associated with signs of fibrosis.

Most frequent COVID- 19 pneumonia features were consolidation (CONS) in the lower lobes; CONS with central/peripheral or patchy distributions; anterior and posterior CONS; and rounded-shaped GGOs in the lower lobes.

After multivariate analysis, CONS in the lower lobes and signs of fibrosis in GGO in the lower lobes remained independently associated with COVID-19 pneumonia or SSc-ILD, respectively.

Based on the findings, the team created a predictive risk score with a 96.1% sensitivity and 83.3% specificity for a COVID-19 diagnosis. Four points were assigned if CONS was present, 0 if not present; GGO without fibrosis received 5 points, 0 points with fibrosis; and 3 points if absent. A score of 4 or more was associated with a COVID-19 diagnosis.

According to the authors, the score showed an excellent predictive capability, with an area under the ROC curve of 0.97. The negative predictive value was 95.2% (83.8% -99.4% CI), and the positive predictive value was 86.0%.

Because there was little interreader agreement (0.03-0.36) on the various items requested in the study, this aspect of the study was not further evaluated.

Matucci-Cerinic said the team currently is studying the shared pathogenetic pathways of both diseases (https://bit.ly/3AD4UJa).

Dr. Shelley Schmidt, Director of the Pulmonary Fibrosis Care Center at Spectrum Health in Grand Rapids, Michigan commented in an email to Reuters Health, "Identifying radiographic hallmarks that distinguish an enduring COVID-19-related lung injury from other causes of chronic lung injury would be incredibly useful in the COVID era. This is especially so if the patient later develops respiratory symptoms without clear, radiographic evidence of lung disease during their initial COVID-19 infection, or if their symptoms and radiographic changes completely resolved post-infection, only to recur. We risk blaming a distant COVID-19 infection when another, treatable cause of their lung injury could be present."

"As physicians and health systems, we need to put proper mechanisms in place to heighten vigilance in our patient evaluations, in spite of the COVID-19 tidal wave, to accurately diagnose treatable conditions," Dr. Schmidt concluded.

Dr. Benjamin Tabibian of the University of California, Riverside also commented by email. "A bit less than one in three of SSc-ILD patients have a usual interstitial pneumonia pattern, which is less likely to be confused with COVID-19. It's unclear what the rate of correct diagnosis would have been with those patients excluded. This may have been clearer with a specific focus on non-specific interstitial pneumonia."

"SSc-ILD can easily be mistaken for COVID-19 even by chest radiologists," he noted. "This study noted common findings more specific to each individual diagnosis, which may be useful in differentiating between these two similar appearing conditions."

"Given the reasonably good sensitivity of COVID-19 screening, these findings may be useful in addressing patients who may need repeat screening or additional workup for ILD," he added. "As with most radiographic findings, 'clinical correlation' is required."

SOURCE: https://bit.ly/3CL05Pw Rheumatology, online July 28, 2021.

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