Clinical utility of chest radiography for severe COVID-19

Abstract

Background: Chest radiography (CXR) is performed more widely and readily than CT for the management of coronavirus disease (COVID-19), but there remains little data on its clinical utility. This study aims to assess the diagnostic performance of CXR, with emphasis on its predictive value, for severe COVID-19 disease.

Methods: A retrospective cohort study was conducted, 358 chest radiographs were performed on 109 COVID-19 patients (median age 44.4 years, 58 males and 30 with comorbidities) admitted between 22 January 2020 and 15 March 2020. Each CXR was reviewed and scored by three radiologists in consensus using a 72-point COVID-19 Radiographic Score (CRS). Disease severity was determined by the need for supplemental oxygen and mechanical ventilation.

Results: Patients who needed supplemental oxygen (n=19, 17.4%) were significantly older (P<0.001) and significantly more of them had co-morbidities (P=0.011). They also had higher C-reactive protein (CRP) (P<0.001), higher lactate dehydrogenase (LDH) (P<0.001), lower lymphocyte count (P<0.001) and lower hemoglobin (Hb) (P=0.001). Their initial (CRS_initial) and maximal CRS (CRS_max) were higher (P<0.001). Adjusting for age and baseline hemoglobin, the AUROC of CRS_max (0.983) was as high as CRP_max (0.987) and higher than the AUROC for lymphocyte count_min (0.897), and LDH_max (0.900). The AUROC for CRS_initial was slightly lower (0.930). CRS_initial ≥5 had a sensitivity of 63% and specificity of 92% in predicting the need for oxygen, and 73% sensitivity and 88% specificity in predicting the need for mechanical ventilation. CRS between the 6^th and 10^th day from the onset of symptoms (CRS_D6-10) ≥5 had a sensitivity of 89% and specificity of 95% in predicting the need for oxygen, and 100% sensitivity and 86% specificity in predicting the need for mechanical ventilation.

Conclusions: Adjusting for key confounders of age and baseline Hb, CRS_max performed comparable to or better than laboratory markers in the diagnosis of severe disease. CXR performed between the 6^th and 10^th days from symptom onset was a better predictor of severe disease than CXR performed earlier at presentation. A benign clinical course was seen in CXR that were normal or had very mild abnormalities.

Keywords: Radiography; pneumonia; thoracic; viruses.

Figure 1

How COVID-19 Radiographic Score was calculated in the initial chest radiograph of a 71-year-old Chinese man with COVID-19: the patient had a past medical history of hypertension and presented to our institution with fever, shortness of breath and diarrhoea (day 6 of symptoms onset). On CXR, the right upper zone was graded 0 (no opacity), right middle zone was graded 1 (<25% opacity) with grade 1 density (hazy), right lower zone was graded 3 (50–74% opacity) with grade 2 density, left upper zone was graded 0, left middle zone was graded 1 (<25% opacity) with grade 1 density (hazy), left lower zone was graded 4 with grade 2 density. A CRS of 16 (1+6+1+8) was obtained. The patient’s oxygen saturation was 93% on arrival and he was started on supplemental oxygen. The patient’s disease worsened and he was intubated on day 9 of symptom onset.

Figure 2

Correlation of ground-glass opacities between CXR and CT: a 36-year-old Chinese woman with no past medical history, who presents to hospital on day 6 of COVID-19 infection. (A) Chest radiograph on day 14 from symptom onset was scored as follows: right upper zone grade 1 with grade 1 density, right lower zone grade 2 with grade 1 density, left middle zone grade 1 with grade 1 density and left lower zone grade 1 with grade 1 density, CRS score of 5; (B) CT abdomen and pelvis performed on day 15, for abdominal pain, confirmed patchy ground-glass attenuation of the lower lobes, worse on the right. CXR, chest radiography.

Figure 3

Correlation of consolidation between CXR and CT: a 68-year-old Chinese man with COVID-19, and relevant past medical history of smoking and hypertension, presented with shortness of breath on day 14 of symptom onset. He presented with an oxygen saturation of 85% on room air and was intubated on arrival. (A) Initial chest radiograph was scored as follows: right middle zone grade 1 density score 2, right lower zone grade 3 density score 3, left middle zone grade 4 density score 3 and left lower zone grade 4 density score 2 (CRS 31); (B) CT thorax done on the same date confirmed dense consolidation in both lungs, worse in the lower lobes.

Figure 4

Scatterplot diagrams illustrate relationships between maximum COVID-19 Radiographic Score and (A) maximum CRP, (B) maximum LDH and (C) lowest lymphocyte count. CRP, C-reactive protein; LDH, Lactate dehydrogenase.