Impact of Thymic Response in COVID-19 Pneumonia on Disease Severity and Mortality-As Assessed on CT-Chest

Objective: To determine the effect of thymic response to COVID-19 pneumonia on imaging and its impact on disease severity and outcome. Study Design: Cross-sectional study. Place and Duration of Study: Armed Forces Institute of Radiology and Imaging (AFIRI), Rawalpindi Pakistan, from Mar to Jul 2020. Methodology: A total of 1620 COVID-19 patients above the age of 18, of either gender, were included in the study. Their findings on High-Resolution CT (HRCT) chest were recorded and graded according to the CT severity score (CTSS) out of a total of 40;less than or equal to 19 was taken as mild while >20 scores were considered as severe disease. The thymic response was assessed by imaging appearance on CT and was graded from 0-3 as follows: fatty, predominantly fatty, mixed density (fat and soft density), and soft density. Fatty replacement implied thymic involution, while soft density depicted a reactivation of thymic tissue after a disease process depictive adequate thymic response. Results: A significant difference in thymic response was observed in patients of different age groups (p<0.001), with the younger age group demonstrating thymic reactivation/ response in the majority (170/244, 69.7%). CT severity score and mortality were significantly higher in older patients demonstrating poor thymic response to COVID pneumonia. Conclusion: Response of the thymus to acute viral infection by Sars COVID-19 is impaired as age progresses;this accounts for greater disease severity, morbidity and mortality in older patients.

SPECTRUM OF CHEST X-RAY FINDINGS IN COVID-19 POSITIVE PATIENTS UTILIZING MODIFIED RALE SCORE FOR SEVERITY ASSESSMENT

ABSTRACT Objective: To assess chest x-ray appearance of patients with positive RT-PCR test for SARS-Cov-2 and utilize modified RALE score for severity assessment of chest x-ray findings for correlation with clinical spectrum of disease. Study Design: Prospective observational study. Place and Duration of Study: Armed Forces Institute of Radiology and Imaging, Pak Emirates Military Hospital, Rawalpindi, from Apr 2020 to May 2020. Methodology: First 1000 consecutive chest x-rays of COVID-19 patients with RT-PCR confirmation at our setup were analyzed. Positive chest x-rays were assessed for consolidation, ground glass opacities and location of involvement. A severity index using modified RALE score was calculated for each and both lungs. Results: Nine hundred and thirty two patients were males and 68 were females with an average age of 40.77 years ± 13.58. Out of 1000 patients, 759 (75.9%) had normal chest x-rays. Two hundred and forty one patients had positive findings, ground glass opacities being the most frequent feature 211 (87.6%) showing peripheral 219 (90.9%), bilateral 182 (75.5%) and lower zone predominance 221 (91.7%). The optimal modified RALE score threshold for recognizing severe disease was 4.5 (area under curve, 0.943), with 79.2% sensitivity and 96.3% specificity. Conclusion: COVID-19 patients with positive chest x-ray findings frequently showed ground glass opacities with bilateral lower zone involvement in peripheral distribution. Modified RALE score can be used for objective evaluation of clinically severe patients.