Diagnostic performance of standard and inverted grey-scale CXR in detection of lung lesions in COVID-19 patients. A single institution study in the region of Abu Dhabi

Purpose To evaluate diagnostic performance of greyscale and inverted greyscale Chest X-ray (CXR) using Computed Tomography (CT) scan as a gold standard. Methods In this retrospective study, electronic medical records of 120 patients who had valid CXR and High-resolution CT (HRCT) within less than 24 hours after having a positive COVID-19 RT-PCR test during the period from May 19 th to May 23 rd 2020 in a single tertiary care center were reviewed. PA chest radiographs were presented on 2 occasions to 5 radiologists to evaluate the role and appropriateness of greyscale and inverted greyscale chest radiographs (CXR). The images were viewed on high-specification viewing systems using a primary display monitors and compared it to computed tomography (CT) findings for screening and management of suspected or confirmed COVID-19 patients. Results Ninety-six (80%) patients had positive CT findings, 81 (67.5%) had positive grey scale CXR lesions, and 25 (20.8%) had better detection in the inverted grey scale CXR. The CXR sensitivity for COVID-19 pneumonia was 93.8% (95% CI (86.2% - 98.0%) and the specificity was 48.7% (95% CI (32.4% - 65.2%). The CXR sensitivity of detection of lung lesions was slightly higher in male (95.1% (95% CI (86.3% - 99.0%)) than female (90.0% (95% CI (68.3% - 98.8%)), while the specificity was 48.0% (95% CI (27.8% - 68.7%) and 50.0% (95% CI (23.0% - 77.0%) in males and females, respectively. However, no significant difference was detected in ROC area between men and women. Conclusions The sensitivity of detection of lung lesions of CXR was relatively high, particularly in men. The results of the study support the idea of considering conventional radiographs as an important diagnostic tool in suspected COVID-19 patients especially in healthcare facilities where there is no access to HRCT scans. Highlights CXR shows high sensitivity for detecting lung lesions in HRCT confirmed COVID-19 patients. Better detection of lesions was noted in the inverted grey scale CXR in (20.8%) of cases with positive findings in standard greyscale CXR. Conventional radiographs can be used as diagnostic tools in suspected COVID-19 patients especially in healthcare facilities where there is no access to HRCT scans.