Baseline chest X-ray in coronavirus disease 19 (COVID-19) patients: association with clinical and laboratory data

Abstract

Purpose: To assess the reliability of CXR and to describe CXR findings and clinical and laboratory characteristics associated with positive and negative CXR.

Methods: Retrospective two-center study on consecutive patients admitted to the emergency department of two north-western Italian hospitals in March 2020 with clinical suspicion of COVID-19 confirmed by RT-PCR and who underwent CXR within 24 h of the swab execution. 260 patients (61% male, 62.8 ± 15.8 year) were enrolled. CXRs were rated as positive (CXR+) or negative (CXR-), and features reported included presence and distribution of airspace opacities, pleural effusion and reduction in lung volumes. Clinical and laboratory data were collected. Statistical analysis was performed with nonparametric tests, binary logistic regression (BLR) and ROC curve analysis.

Results: Sensitivity of CXR was 61.1% (95%CI 55-67%) with a typical presence of bilateral (62.3%) airspace opacification, more often with a lower zone (88.7%) and peripheral (43.4%) distribution. At univariate analysis, several factors were found to differ significantly between CXR+ and CXR-. The BLR confirmed as significant predictors only lactate dehydrogenase (LDH), C-reactive protein (CRP) and interval between the onset of symptoms and the execution of CXR. The ROC curve procedure determined that CRX+ was associated with LDH > 500 UI/L (AUC = 0.878), CRP > 30 mg/L (AUC = 0.830) and interval between the onset of symptoms and the execution of CXR > 4 days (AUC = 0.75). The presence of two out of three of the above-mentioned predictors resulted in CXR+ in 92.5% of cases, whereas their absence in 7.4%.

Conclusion: CXR has a low sensitivity. LDH, CRP and interval between the onset of symptoms and the execution of CXR are major predictors for a positive CXR.

Keywords: Chest X-ray; Coronavirus disease 2019 (COVID-19); Laboratory test; Real-time reverse transcriptase-polymerase reaction chain test (RT-PCR); Sensitivity; Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Fig. 1

Study flow chart

Fig. 2

ROC curves for the discriminating ability of lactate dehydrogenase (LDH) AUC = 0.88; C-reactive protein (CRP), AUC = 0.83; and Number of days (days) between the onset of symptoms and the execution of CXR, AUC = 0.75

Fig. 3

Odds Ratio 95%CIs of the three predictors for agreement of CXR with RT-PCR. 95%CIs completely above 1 correspond to positive effect on CXR+; completely below 1 correspond to adverse effects; including 1 to randomity

Fig. 4

Baseline chest X-ray finding in COVID-19 patients associated with clinical and laboratory data. a 47-year-old man, without comorbidities, presented with fever, cough, rhinitis and conjunctivitis for 3 days. Laboratory test: Lymphocytes 1.31 (10⁹/L), CRP = 8.3 mg/L and LDH = 330 UI/L. The chest X-ray resulted negative. b 46-year-old man, without comorbidities, presented with fever, cough, and Pharyngodynia for 1 days. Laboratory test: Lymphocytes 0.8 (10⁹/L), CRP = 3 mg/L and LDH = 346 UI/L. The chest X-ray resulted negative. c 58-year-old man, without comorbidities, presented with fever and cough for 7 days. Laboratory test: Lymphocytes 0.67 (10⁹/L), CRP = 141.9 mg/L and LDH = 711 UI/L. The chest X-ray resulted positive with peripheral airspace opacification in the left lower lobe. D: 55-year-old woman, without comorbidities, presented with fever and cough for 7 days. Laboratory test: Lymphocytes 1.13 (10⁹/L), CRP = 60.9 mg/L and LDH = 784 UI/L. The chest X-ray resulted positive with neither peripheral nor perihilar airspace opacification with middle and lower zone involvement