Low Sensitivity of Admission Lung US Compared to Chest CT for Diagnosis of Lung Involvement in a Cohort of 82 Patients with COVID-19 Pneumonia

Abstract

Background and Objectives: The potential role of lung ultrasound (LUS) in characterizing lung involvement in Coronavirus disease 2019 (COVID-19) is still debated. The aim of the study was to estimate sensitivity of admission LUS for the detection of SARS-CoV-2 lung involvement using Chest-CT (Computed Tomography) as reference standard in order to assess LUS usefulness in ruling out COVID-19 pneumonia in the Emergency Department (ED). Methods: Eighty-two patients with confirmed COVID-19 and signs of lung involvement on Chest-CT were consecutively admitted to our hospital and recruited in the study. Chest-CT and LUS examination were concurrently performed within the first 6-12h from admission. Sensitivity of LUS was calculated using CT findings as a reference standard. Results: Global LUS sensitivity in detecting COVID-19 pulmonary lesions was 52%. LUS sensitivity ranged from 8% in case of focal and sporadic ground-glass opacities (mild disease), to 52% for a crazy-paving pattern (moderate disease) and up to 100% in case of extensive subpleural consolidations (severe disease), although LUS was not always able to detect all the consolidations assessed at Chest-CT. LUS sensitivity was higher in detecting a typical Chest-CT pattern (60%) and abnormalities showing a middle-lower zone predominance (79%). Conclusions: As admission LUS may result falsely negative in most cases, it should not be considered as a reliable imaging tool in ruling out COVID-19 pneumonia in patients presenting in ED. It may at least represent an expanded clinical evaluation that needs integration with other diagnostic tests (e.g., nasopharyngeal swab, Chest-CT).

Keywords: COVID-19; Chest-CT; SARS-CoV-2 pneumonia; interstitial pneumonia; lung ultrasound (LUS); sensitivity.

Figure 1

A 41-year-old male, presented with a one week history of persistent and worsening dry cough and fever with fatigue. The RT-PCR assay for the SARS-COV-2 showed a positive result. Computed Tomography (CT) scans in (A,C,E) show a diffuse pure bilateral ground glass opacity (GGO), also peripherally distributed, but not adherent to pleural surface. Ultrasound scans in (B,D,F) (corresponding to the blue boxes in the respective (A,C,E) CT scans), with a convex probe (6 MHz) and thoracic setting, do not show any pathologic pattern. The hyperechoic pleural line is highlighted by a white arrow.

Figure 2

A 78-year-old male patient presenting with fever and cough for 10 days. The RT-PCR assay confirmed the suspect for COVID-19 pneumonia. The peripheral subpleural consolidation showed in (A) CT scan was in part located in the retroscapular area (blue box). The corresponding ultrasound scan with a convex probe (6 MHz) and thoracic setting in (B) allows us to view its non-retroscapular part as a mixed hyper-hypoechoic subpleural area (white arrows). Not all of the consolidations shown in (C,E,G) CT scans were adherent to the pleural surface (blue boxes). The corresponding ultrasound scans with a convex probe (6 MHz) and thoracic setting in (D,F) show a thickened hyperechoic pleural line (yellow arrow), with a mixed hypo-echoic subpleural consolidation (white arrow), that represent the adherent to the pleural surface part of these consolidations. On the contrary, ultrasound scan in (H) allows us to view only a blurred and thickened hyperechoic pleural line (yellow arrow), with B line below it (white arrow).