Clinical usefulness of tomographic standards for COVID-19 pneumonia diagnosis: Experience from a Brazilian reference center

Abstract

Background: COVID-19 is a new disease and the most common complication is pneumonia. The Radiological Society of North America (RSNA) proposed an expert consensus for imaging classification for COVID-19 pneumonia.

Objective: To evaluate sensitivity, specificity, accuracy, and reproducibility of chest CT standards in the beginning of the Brazilian COVID-19 outbreak.

Methods: Cross-sectional study performed from March 1st to April 14th, 2020. Patients with suspected COVID-19 pneumonia submitted to RT-PCR test and chest computed tomography (CT) were included. Two thoracic radiologists blinded for RT-PCR and clinical and laboratory results classified every patient scan according to the RSNA expert consensus. A third thoracic radiologist also evaluated in case of discordance, and consensus was reached among the three radiologists. A typical appearance was considered a positive chest CT for COVID-19 pneumonia. Sensitivity, specificity, positive and negative predictive values were calculated. Cohen's kappa coefficient was used to evaluate intra- and inter-rater agreements.

Results: A total of 159 patients were included (mean age 57.9 ± 18.0 years; 88 [55.3%] males): 86 (54.1%) COVID-19 and 73 (45.9%) non-COVID-19 patients. Eighty (50.3%) patients had a positive CT for COVID-19 pneumonia. Sensitivity and specificity of typical appearance were 88.3% (95%CI, 79.9-93.5) and 94.5% (95%CI, 86.7-97.8), respectively. Intra- and inter-rater agreement were assessed (Cohen's kappa = 0.924, P = 0.06; Cohen's kappa=0.772, P = 0.05, respectively).

Conclusion: Chest CT categorical classification of COVID-19 findings is reproducible and demonstrates high level of agreement with clinical and RT-PCR diagnosis of COVID-19. In RT-PCR scarcity scenarios or in equivocal cases, it may be useful for attending physicians in the evaluation of suspected COVID-19 pneumonia patients attended at the emergency unit.

Keywords: CT; Coronavirus disease 2019; Diagnosis.; Viral pneumonia.

Fig. 1

Fow diagram of study participants. Abbreviations: RT-PCR, Reverse Transcriptase Polymerase Chain Reaction; SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus 2; COVID-19, coronavirus disease 2019; CT, computed tomography.

Fig. 2

Positive and negative predictive values of a positive chest computed tomography (CT) according to distinct prevalences of COVID-19. A positive chest CT was defined as a typical appearance. Error bars indicate 95% confidence intervals (CI). Positive predictive values (%) and 95% CI according to each estimated prevalence (P): P 10% - 63.6 (40.8-81.9); P 20% - 80.0 (62.5-90.9); P 30% - 87.5 (74.0-94.8); P 40% - 91.8 (81.1-96.9); P 50% - 94.6 (86.0-98.2); P 60% - 96.5 (89.5-99.1); P 70% - 98.0 (92.2-99.6); P 80% - 98.2 (93.1-99.7); P 90% - 99.2 (95.0-99.9). Negative predictive values (%) and 95% CI according to each estimated prevalence (P): P 10% - 98.5 (94.3-99.7); P 20% - 96.7 (91.4 - 98.9); P 30% - 94.6 (88.1-97.7); P 40% - 92.7 (85.2-96.8); P 50% - 89.3 (80.1-94.6); P 60% - 84.5 (73.5-91.6); P 70% - 77.6 (64.4-87.0); P 80% - 66.6 (50.9-79.5); P 90% - 46.8 (29.5-64.9).

Fig. 3

Nonenhanced high-resolution chest CT of different patients with confirmed COVID-19 pneumonia and typical findings. A, 74-year-old man presented with 7-day history of fever and cough. Axial CT shows multifocal, peripheral and rounded ground glass opacities (GGO). B, 47-year-old man presented with 10-day history of moderate breathlessness and fever. Axial CT shows reversed halo sign. C, 70-year-old woman presented with 9-day history of mild dyspnea and COVID-19 exposure. Axial CT shows GGO with a perilobular pattern. D, 36-year-old man presented with 5-day history of fever, cough and myalgia. Axial CT shows bilateral areas of crazy-paving pattern.

Fig. 4

Nonenhanced high-resolution chest CT of different patients with atypical findings. A, 52-year-old man presented with 3-day history of fever, cough and adynamia. Axial chest CT shows centrilobular nodules, tree-in-bud opacities and bronchial mucocele. The patient was diagnosed with pulmonary tuberculosis. B, 26-year-old woman presented with 10-day history of cough, sputum, fever and dyspnea. Axial chest CT shows lobar consolidation. The patient was diagnosed with bacterial acquired community pneumonia. C, 47-year-old woman presented with 30-day history of headache, adynamia, cough and chest pain. Axial chest CT shows pulmonary cavitation with satellite centrilobular opacities. The patient was diagnosed with central nervous system and pulmonary cryptococcosis. D, 55-year-old man presented with 3-day history of orthopnea, precordial pain and cough. Axial chest CT shows bilateral pleural effusion, interlobular septal thickening, and centrilobular ground glass opacities. The patient was diagnosed with congestive heart failure due to myocardial infarction.

Fig. 5

Nonenhanced high-resolution chest CT of different patients with indeterminate findings. A, 40-year-old man presented with 5-day history of worsening of chronic cough, dyspnea and fever. Axial CT shows diffuse and bilateral ground glass opacities. The patient was diagnosed with acquired immunodeficiency syndrome and Pneumocystis pneumonia. B, 55-year-old man presented with 3-day history of cough and mild breathlessness. Axial CT shows unilobar, rounded and peribroncovascular ground glass opacity. COVID-19 pneumonia was confirmed.

Fig. 6

Nonenhanced high-resolution chest CT of a 79-year-old man presented with 7-day history of dyspnea, adynamia and COVID-19 exposure (wife and job colleague diagnosed with SARS-CoV-2 pneumonia). A and B, axial, C, sagittal chest CT shows a typical appearance, with bilateral and rounded ground-glass opacities with predominant peripheral distribution. The diagnosis of COVID-19 pneumonia couldn't be ruled out, even though with two negative RT-PCR. The patient had no alternative diagnosis during hospitalization and he obtained complete resolution mptoms and CT findings in a 6-month follow-up visit.