Due to COVID-19 outbreak, The French president eventually decreed a national lockdown on March 16, 2020, i.e. at the beginning of week 12.
The primary interest of our study is to confirm, through a cohort of more than 50 centres, the significant decrease of radiological procedures in ER , during the COVID lockdown, especially for trauma, suspicion of stroke, appendicitis, renal colic and sigmoiditis.
In our series, all the examinations (except those concerning the "chest" region) showed a significant decrease during lockdown.
In particular, the number of stroke examinations decreased by 36%, which is similar to the data from the study by Kansagra et al. (39%) .
By contrast, the decrease in our study was greater than that found in Kerleroux et al. study  which showed a 21% decrease in thrombectomies. This may suggest that patients with minor or regressive symptoms had less options to access emergency services.
According to the Santé Publique France report of 2020 calendar week 16, the number of emergency department visits and hospitalizations for stroke decreased by approximately 27% as compared to the same period in 2019 .
Concerning ANTAPs, the number of examinations decreased by 29% for no apparent reason, and for renal colic, the decrease in the number of examinations could be related to codified and well-known medical treatments which can be more easily managed on an outpatient basis. Additionally, its recurrence is frequent and patients recognize the symptoms without having to go to an emergency department. For appendicitis and sigmoiditis, a clinical presentation without signs of severity may have gone unnoticed or been medically treated by their general practitioner.
Indeed, several articles show that non-surgical treatment of acute appendicitis is an effective and reasonable approach for certain groups of patients and has no resultant increase in the number of complications [12,13,14].
For the CTr and Body-CT sectors, the number of examinations decreased by 52% and 62%, respectively. This decrease was predictable due to an almost complete cessation of outdoor activities, travel and associated car accidents. These figures corroborated with the road safety indicators of March 2020 which announced 43.2% fewer injury accidents as compared to March 2019.
Our results showed a worrisome overall drop in the number of examinations in the stroke and ANTAP sectors over a large part of France during the first 4 weeks of lockdown. Since we experienced similar decreases in normal and pathological examinations (stable percentage of positivity), the relevance of examinations was not higher. This does not prejudge the severity of patients with a pathological examination, and we were not able to specifically study this severity patterns.
Our study shows that patients did not access emergency room services, either renouncing or having no access to care (unavailability of medical referents and/or misdirection of the emergency call centres by misunderstanding the patients’ complaints). This situation can have dramatic effects because the access to emergency department services is necessary for these patients.
This phenomenon can be explained by several factors such as the patient’s overriding fear of exposure to COVID-19, despite their medical symptoms. This phenomenon also occurred during the 2003 SARS epidemic in Asia when there was a recorded average reduction of 30–50% in all non-critical emergency department visits [15,16,17].
Additionally, the pandemic’s resultant strain on emergency department facilities and/or closure of many doctors’ office, along with reduced public transportation added to the difficulty of accessing emergency department services . This phenomenon no doubt was exacerbated by policy recommendations to avoid disturbing the medical staff who were already overburdened by the pandemic.
In the weeks following the end of lockdown, we will need to document the return to using emergency department services, the resultant delay in treatments, increased sequelae and increased cardiovascular mortality.
In order to anticipate and document this phenomenon during any future lockdown, it will be important to establish and follow indicators so as to reinforce the public health messages for other medical problems (stroke in particular) concomitantly with those related to the epidemic. Additionally, the health care system will need to adapt and the private and public sectors will have to strengthen their collaboration. For example, separating “pandemic” hospitals/clinics from clean hospitals/clinics could be an appropriate solution, to be dealt with in a territorial perspective. Besides, the development of telemedicine/teleconsultations solutions will help maintain access to care for appropriate medical conditions.
The significant increase in the tests involving the "chest" region directly reflects the peak of the outbreak and the importance of diagnostic CT scans . This requires a major reorganization of radiological structures in general and teleradiological structures in particular.
Expertise in chest imaging varies and, in order to maintain, or even improve diagnostic performances, specific training actions must also be anticipated.
Our study contains the biases of a retrospective multi-centre data collection. However, the extent of recruitment on French territory and the homogeneity of the data collected through our specific and structured sectors reinforces the accuracy of our results.
Teleradiology appears to be a relevant indirect indicator of the impact of the COVID-19 pandemic management on the activities of emergency department services.