Diagnostic efficacy of chest xray and hrct in detection of covid-19 pneumonia: a study in tertiary care covid hospital, kolkata

Introduction: World is battling through a global pandemic of unprecedented extent which has posed perhaps the most serious threat to the mankind in modern times. The epicenter of the global catastrophe was Wuhan, China from where the new virus by the name of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has spread over 188 countries and caused a death toll of over 2.16 million till now. Chest Radiography has very limited role in diagnosis of early and mild course of disease. However it showed significant efficacy in diagnosing intermediate to advanced stages of the disease as well as during follow-up. CT on the other hand has shown promising sensitivity values and has been the mainstay of imaging diagnosis of Covid-19 cases, even in RT-PCR negative patients.
Purpose: The purpose of our study is to correlate chest x-ray and HRCT Thorax findings with RT-PCR, describe various chest x-ray & CT findings and monitor patient’s disease progression over time.
Materials and Methods: The study was done in the department of Radio diagnosis, Medical College Kolkata, a dedicated tertiary level Covid-19 hospital. We selected 50 patients from 10th April to 10th August, 2020 who had symptoms of COVID-19 (fever, cough, sore throat, dyspnoea). All patients performed RT-PCR nasopharyngeal and throat swab, CXR on admission and during follow-up and HRCT Thorax. RT-PCR results were considered the reference standard. A CXR severity scoring index and CT Severity score were determined for each lung. A total severity score was calculated by summing both lung scores.
Results: The study was composed of 50 clinically suspected patients, all of whom tested positive for COVID-19 by RT-PCR. 26 of 140 RT-PCR positive patients at initial scan and 6 patients in follow-up scan showed chest X-ray abnormalities. Most common findings of chest X-ray were consolidation (65.6%) followed by ground glass opacity (34.4%), reticulation and interstitial thickening (31.3%). Pleural effusion was found in 4 patients (12.5%). Most cases showed peripheral predominance (62.5%) with Bilateral lung involvement (74%) and lower zonal (78.1%) distribution. Total severity scores ranged from 0 to 8 and calculated at baseline, first week and second week of follow-up scan. Peak severity was reached at 12-14 days of disease onset. The typical findings on CT as studied were ground-glass opacities (96%) being the most common finding almost in every patient, followed by bronchovascular thickening (76%), air space consolidation (64%) and crazy paving appearance (50%). Patients with pre-existing comorbidities were found to be more prone to develop severe form of the disease with 5 out of 12 patients with diabetes and 3 out of 9 patients with hypertension having severe CT severity scores. By using RT-PCR results as standard, overall sensitivity of chest radiography and CT Thorax were 68% and 100% respectively in the diagnosis of COVID-19.
Conclusions: Chest radiography can be used as initial diagnostic tool for triaging of COVID-19 in symptomatic patients and useful for monitoring chest manifestations and extent of lung involvement and disease progression over time. CT has substantially improved diagnostic performance over CXR in COVID-19. CT should be strongly considered in the initial assessment for suspected COVID-19. This gives potential for increased sensitivity and considerably faster turnaround time, where capacity allows and balanced against excess radiation exposure risk.