Systemic sclerosis-related interstitial lung disease (SSc-ILD) can be differentiated from COVID-19 lung disease with the help of CT scan, according to a new study reported in the journal Rheumatology.¹

The retrospective, observational, multicentric, international study included 99 patients (52 patients with COVID-19 pneumonia and 47 patients with SSc-ILD).

Examination of CT scans of the participants showed that the most frequent findings on CT predictive of SSc-ILD according to clinical decision, feasibility, good reproducibility and good/excellent predictive ability were fibrosis inside focal ground glass opacities (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.

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 were the CT features most frequently associated with COVID- 19 pneumonia.

Based on these findings, a predictive risk score was developed to identify the CT associated with the COVID-19 diagnosis. The score was 0 if there was no consolidation, while the score was 4 if consolidation was present. GGO: 5 points if present without fibrosis, 0 if present with fibrosis, 3 if absent. This score was found to have a negative predictive value of 95.2%, and a positive predictive value of 86.0%.

The presence of consolidation in the lower lobes and signs of fibrosis in GGO in the lower lobes were found to be independently associated with COVID-19 pneumonia or SSc-ILD, respectively demonstrating for the first time, as per the study authors, that CT scan can come to the aid of the clinician in differentiating between the two conditions.

SSc-ILD can easily be mistaken for COVID-19 to the inexperienced eye. While a clinical correlation is essential, these findings may help to identify patients who may need repeat screening or additional workup for ILD. Fever and sudden onset of dyspnea are typically associated with COVID-19 pneumonia. However, as the authors say, “suspicion for a SARS-CoV-2 infection in symptomatic SSc patients should be raised also in the absence of fever, since in most of these patients, fever is absent due to treatment with immunosuppressors”. On an SSc-ILD background, the appearance of rounded GGO may raise the suspicion of a COVID-19 overlapping on SSc-ILD.

Reference

1. Orland M, et al. The role of chest CT in deciphering interstitial lung involvement: systemic sclerosis versus COVID-19. Rheumatology (Oxford). 2021 Jul 28;keab615. doi: 10.1093/rheumatology/keab615.

Dr Surya Kant,

Professor and Head, Dept. of Respiratory Medicine, KGMU, UP, Lucknow.National Vice Chairman IMA-AMS