Use of Chest Imaging in the Diagnosis and Management of COVID-19: A WHO Rapid Advice Guide



# Introduction
A cluster of pneumonia cases in Wuhan, China was first reported to the World Health Organization (WHO) Country Office in China on 31 st of December 2019. Soon thereafter, a novel coronavirus was identified as the causative agent . This virus was named severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and the associated disease was named coronavirus disease 2019 (COVID-19) . Since December 2019, COVID-19 has rapidly spread from Wuhan to other parts of China and throughout the world. On 30 January 2020, WHO declared the outbreak a public health emergency of international concern and on 11 March 2020, WHO characterized the outbreak as a pandemic .
The diagnosis of COVID-19 is currently confirmed by identification of viral RNA in reverse transcriptase polymerase chain reaction (RT-PCR). Chest imaging has been considered as part of the diagnostic workup of symptomatic subjects with suspected COVID-19 in settings where laboratory testing (RT-PCR) is not available or results are delayed or are initially negative in the presence of symptoms attributable to COVID-19.
COVID-19 manifests with non-respiratory symptoms as well as respiratory symptoms which are nonspecific and of variable severity, ranging from mild to life threatening, which may demand advanced respiratory assistance and artificial ventilation. Imaging has been also considered to complement clinical evaluation and laboratory parameters in the management of patients already diagnosed with COVID-19 (1).
A recent international survey conducted by the International Society of Radiology and the European Society of Radiology found important variations in imaging practices related to COVID-19 .
Several countries requested WHO's advice on the role of chest imaging in the diagnostic workup of subjects with suspected or probable COVID-19 disease and in the clinical management of patients with confirmed COVID-19. As a consequence, WHO undertook the development of a rapid guide on the use of chest imaging in the diagnosis and management of COVID-19 .

# Methods

## I n p r e s s
The development of this rapid advice guide followed the process outlined in the WHO handbook for guideline development , which used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology . Given the nature of the emergency, the process was implemented within a time frame of two months. The reporting of this guide followed the Reporting Items for practice Guidelines in HealThcare (RIGHT) checklist . The main target audience of the guidance are health professionals involved in the diagnosis and management of COVID-19.

## Group composition
In conformity with the WHO process, the following bodies were established: a core group (coordination role), a steering group (advisory role), a guideline development group (GDG; the expert panel) and an external review group (peer review role). Membership of the GDG and the external review group included experts from 10 high income countries and 14 low-and middle-income countries (LMICs). In addition, a systematic review team was contracted to conduct a rapid systematic review for each of the guidance's questions. Appendix E1 provides the details on group composition and roles and list of contributors.

## Management of declaration of interests
All experts declared their interests prior to participation in the guideline development processes and meetings. All declarations were managed following WHO regulations, on a case-by-case basis and communicated to the experts at the start of the first GDG meeting. A summary was included in Appendix E2. All authors have completed the ICMJE uniform disclosure form at ww.icmje.org/coi_disclosure.pdf and declare no conflicts.

## Identification of the key questions
The core group reviewed formal consensus statements from professional bodies and/or national health authorities on the use of chest imaging in COVID-19, with the assistance of the GDG and the International Society of Radiology. Informed by these statements , the core group formulated the key questions using the PICO format (Population, Intervention, Comparator, Outcomes), with the help of the steering group, the GDG and the systematic review team (see Appendix E3). The intended I n P r e s s PICO 2: The systematic review identified 23 studies that evaluated the diagnostic accuracy of three imaging modalities in symptomatic patients with suspected COVID-19, against a reference standard, chest radiography (n=3), chest CT (n=19) and lung ultrasound (n=1). None of these studies compared two imaging modalities against each other. The systematic review team judged those studies to be at either high risk of bias (n=17) or moderate risk of bias (n=6). The studies provided limited information regarding clinical presentation (e.g. the severity of symptoms at presentation) and few reported specific criteria for a positive imaging test for COVID-19. Eleven studies did not describe a reference standard to diagnose COVID-19 that included serial RT-PCR or clinical follow-up. The median sensitivity and specificity reported by the included studies were 0.64 and 0.82 for chest radiography; 0.92 and 0.56 for chest CT; and 0.95 and 0.83 for lung ultrasound. The systematic review team judged the certainty of this evidence to be low for chest radiography, chest CT and lung ultrasound. The corresponding evidence-to-decision table available in Appendix E4 provides the counts for true positives, true negatives, false positives and false negatives for four hypothetical prevalence values of COVID-19 infection which were assumed to be 20%, 40%, 60% and 80% among symptomatic patients with suspected COVID-19. The update of the review conducted before the publication of the guide identified five new studies that evaluated the diagnostic accuracy of chest radiography, chest CT and lung ultrasound in symptomatic patients with suspected COVID-19. The synthesized evidence as well as its associated certainty were judged to remain unchanged. PICO 3: The systematic review identified no eligible study that evaluated any chest imaging modality in patients with suspected or confirmed COVID-19 not yet hospitalized to support decisions on hospital admission versus home discharge on health outcomes. PICO 4: The systematic review identified no eligible study that evaluated any chest imaging modality in patients with suspected or confirmed COVID-19 not yet hospitalized to support decisions on regular admission versus intensive care unit admission on health outcomes. The update of the review conducted before the publication of the guide identified one new study that evaluated the use of chest imaging in patients with suspected or confirmed COVID-19 not yet hospitalized. The certainty of the evidence was judged as very low. I n P r e s s PICO 5: The systematic review team identified three studies that evaluated chest imaging in patients currently hospitalized with moderate or severe symptoms and suspected or confirmed COVID-19, for predicting mortality or admission at the intensive care unit. The certainty of evidence was judged to be very low.
PICO 7: The systematic review team identified no study that evaluated any chest imaging modality to support the decision on discharge home.
Refer to the full guideline publication for the citations of studies referred in the summary of evidence .
The GDG developed one recommendation for each PICO question with two exceptions: it developed two recommendations for PICO 2 and developed no recommendation for PICO 6 (due to lack of evidence and the rapidly evolving knowledge related to that question). The recommendations for which no evidence meeting inclusion criteria was identified were labelled as based on expert opinion. presents a summary of the recommendations. All developed recommendations are conditional, which means that the desirable effects were judged to likely outweigh the undesirable effects under certain conditions. One set of these conditions relates to the characteristics of patients who are likely to benefit from the recommended interventions (listed in for each recommendation).
Another set of conditions relates the factors to consider when choosing a specific imaging modality (included in for all recommendations). Appendix E5 provides implementation considerations, monitoring and evaluation considerations, and research priorities for the different recommendations. lists only those implementation considerations that are common across all recommendations.
The evidence-to-decision tables for the different recommendations are included in Appendix E4.

# Discussion
The purpose of the guide is to support WHO Member States in their response to the COVID-19 pandemic by providing up-to-date guidance on use of chest imaging in adult patients with suspected or confirmed COVID-19, including chest radiography, computed tomography and lung ultrasound. It covers the care pathway from outpatient facility or hospital entry to home discharge. The guidance is I n P r e s s provided for patients with different levels of disease severity, from asymptomatic individuals to critically ill patients. Additional guidance on infection prevention and control (IPC) in medical imaging procedures for COVID-19 management is provided in Appendix E6. The IPC guidance addresses both general measures for all imaging procedures and specific precautions for chest radiography, chest CT and lung ultrasound. The guide also promotes quality and safety of radiation use in health facilities, thus enhancing protection and safety of patients and health workers (Appendix E6).
The guide has a number of strengths including its development based on standard methodology [20], the consideration of contextual factors , its reporting according the RIGHT statement, and the consideration of stakeholders views . Limitations include that the evidence on which the recommendations are based is either lacking or at best of low certainty, and that scope is relatively narrow (e.g., excluded children, did not address the systemic aspects of the disease). However, the latter was necessary to allow the rapid development of recommendations addressing the most pressing questions.
The recommendations address chest imaging in general, but not specific imaging modalities. While there is accumulating evidence about typical findings with each imaging modality , evidence about comparative diagnostic and prognostic value of the different modalities is still lacking. The experience indicates that in most cases chest radiography with portable equipment can provide the information needed at the point of care. In addition to limiting patient transfers it gives the possibility of adapting procedures to reduce staff exposure and increase operational efficiencies (e.g. portable chest radiography obtained through the glass of an isolation room door) . Preliminary studies on lung ultrasound seem promising, in particular for use of portable ultrasound scanners at the point of care, but further evidence still needs to be generated. A CT scan may be the indicated modality for particular patient groups (e.g. those with suspected thrombotic/thromboembolic disease, multisystemic disease). In health facilities, particularly in LMICs, where CT scans are not available for those patients, policy makers should consider provisions to facilitate patient transfer to reference hospitals where CT scans can be performed. In the long-term, the assessment of clinical, social, I n P r e s s economic, organizational and ethical issues should inform decision-making about procurement of imaging technology . There is wide variability of the contextual factors across settings (e.g., availability and cost of each modality and availability of the required expertise). Along with other technical considerations, the guide refers to the choice of a chest imaging modality in the remarks that apply to all recommendations (see . Indeed, the GDG gave due consideration to resource use, impact on equity, acceptability and feasibility when drafting the recommendations.
This guide is primarily intended for health professionals working in emergency departments, imaging departments, clinical departments, intensive care units and other health care settings involved in the diagnosis of COVID-19 and in the management of COVID-19 patients. The document can also be useful for hospital managers and planners, policy-makers, hospital architects, biomedical engineers, medical physicists, logistics staff, water/sanitation and infection prevention and control officers.
Health authorities and radiation regulators can use the guide to develop specific national standards relevant to COVID-19 outbreak preparedness, readiness and response in different contexts. Finally, it can be useful to funders that wish to donate equipment and devices as well as funding priority research.
We were able to develop the guideline in about 10 weeks, which fits the 3-month timeframe of 'rapid' guidelines . Two main facilitating factors include the existence of a clear and detailed process in place (as described in the WHO handbook for guideline development) , and the use of a rapid review process . The latter factor is important considering that conducting the systematic review typically consumes a number of months. In addition, we used a staggered approach when developing the guide: e.g., we started training the GDG members even before the findings of the rapid review were available, and we sent out recommendations for peer review (by the external review group) even before all recommendations were developed. Finally, the most critical factor was probably having a dedicated core group that developed and followed a very strict timeline and worked on keeping a steady momentum. The core group members met almost daily (including weekends) and maintained an intense email communication.

## I n p r e s s
While the guide was developed within a relatively short timeframe, we do not believe this has affected the quality of the recommendations. Indeed, we followed standard WHO process, including proper development of PICO questions, determination and prioritization of outcomes of interest, conflicts of interest declaration and management, reliance on systematically collected evidence, use of GRADE methodology, and use of Evidence to Decision tables. While the rapid review could have missed relevant studies, it is very unlikely that any impactful studies have been missed. We did have all members of the GDG verify eligible studies, and we continually monitored the literature over the period of the project. The online format of the GDG meetings, due to the travel restrictions during the pandemic, did not impede proper discussions. On the contrary, GDG discussions were lively constructive and allowed all members the opportunity to contribute.
Moreover, we conducted a survey of stakeholders to capture their views on factors that were very important to the development of recommendations, namely resource use, impact on equity, acceptability and feasibility. The panel paid attention to the resource implications for low resource settings.
As growing body of literature is confirming the multi-systemic nature of COVID-19 (including the nervous, vascular and cardiac systems, kidneys) [28], this raises questions on whether/when/how imaging other than that of the chest (e.g., cardiac ultrasound, brain MRI, vascular imaging, abdominal imaging) may contribute to early diagnosis and/or management of patients with COVID-19.
Specifically, pulmonary embolism in patients with COVID-19 is gaining attention with its relatively high prevalence and the ongoing discussion about its embolic versus intravascular thrombotic mechanism . When addressing this question, the GDG members felt that both the published literature and the collective clinical experience were not adequate to justify any recommendation. We are aiming to address it in the next update of the guide.
In the future, guidance and policies for procurement of imaging equipment are needed. There is also a need for research on diagnostic accuracy, and desirable and undesirable impact of the different

## I n p r e s s
Finally, there is a need for studies addressing contextual factors, including cost, cost effectiveness, impact on equity, acceptability and feasibility of the different imaging modalities.
In summary, the guide provides up-to-date guidance on the use of chest imaging in patients with suspected or confirmed COVID-19 for clinicians, and other stakeholders. It also provides research recommendations that can hopefully provide a better evidence base for future updates of the guide.

## I n p r e s s

## 19.
Alonso-Coello P, Oxman AD, Moberg J, Brignardello-Petersen R, (1) RT-PCR testing is not available;
(2) RT-PCR testing is available, but results are delayed; and
(3) initial RT-PCR testing is negative, but with high clinical of suspicion of COVID-19.

## Conditional recommendation based on low certainty evidence
Imaging should be used as one element of the diagnostic workup that otherwise includes clinical and laboratory data. Patients likely to benefit are those who:
- have presentations that could represent complications of COVID-19, e.g.
pneumonia; pulmonary arterial thrombosis or thromboembolism;
- need to be admitted irrespective of diagnosis (e.g. disease is severe or likely to progress), to help with disposition or triaging (e.g. to dedicated COVID-19 ward versus non-COVID-19 ward);
- need to be transferred to another facility;
- live with people at high risk if infected with COVID-19 (e.g.
immunocompromised, persons aged over 60 years);
- live in small homes, overcrowded households or densely populated settings, where isolation is very difficult to implement;
- live in communities with people at high-risk such as retirement homes or dormitories.
I n P r e s s R3: For patients with suspected or confirmed COVID-19, not currently hospitalized and with mild symptoms, WHO suggests using chest imaging in addition to clinical and laboratory assessment to decide on hospital admission versus home discharge.

## Conditional recommendation, based on expert opinion
Imaging should be used as one element of the patient evaluation that otherwise includes clinical, laboratory and epidemiological data. Patients likely to benefit are those who:
- have or are at high risk of disease progression;
- represent an increased risk of dissemination within their community due to their occupational, social or other circumstances;
- have associated comorbidities (such as diabetes, hypertension, heart disease, obesity) or other chronic diseases which might decompensate and/or are aged over 60 years;
- live with individuals at high risk of morbidity and mortality associated with COVID-19 (e.g., elderly, immunocompromised), whether at home or retirement home;
- live in small homes, overcrowded households or densely populated settings where isolation is very difficult to implement.
- represent an increased risk of dissemination within their community due to their occupational, social or other circumstances.

## Conditional recommendation, based on very low certainty evidence
Imaging should be used as one element of the patient evaluation that otherwise includes clinical and laboratory data. Patients likely to benefit are those who:
- are at higher risk of disease progression (e.g. with comorbidities)
- are not responding to supportive treatment (oxygen supplementation)
- present acute clinical deterioration not elucidated I n P r e s s R5: For patients with suspected or confirmed COVID-19, currently hospitalized and with moderate to severe symptoms, WHO suggests using chest imaging in addition to clinical and laboratory assessment to inform the therapeutic management

## Conditional recommendation, based on very low certainty evidence
Imaging should be used as one element of patient evaluation that otherwise includes clinical and laboratory data. Patients likely to benefit are those who:
- are at high risk of disease progression
- are not responding to treatment (oxygen supplementation)
- have presentations with clinical suspicion of pulmonary fibrosis, pulmonary artery thrombosis or thromboembolism.
R6: For hospitalized patients with COVID-19 whose symptoms are resolved, WHO suggests not using chest imaging in addition to clinical and/or laboratory assessment to inform the decision regarding discharge.

## Conditional recommendation, based on expert opinion
When imaging is used, it should be one element of the patient evaluation that otherwise includes clinical and laboratory data. Patients likely to benefit from chest imaging are those who:
- have had a severe form of COVID-19
- have pre-existing chronic lung disease I n P r e s s Abbreviations: WHO= World Health Organization, COVID-19= coronavirus disease 2019, RT-PCR= reverse transcriptase polymerase chain reaction I n P r e s s . Factors to consider when choosing the specific imaging modality (applies to all recommendations).
 Compared to chest CT, chest radiography appears to have a lower sensitivity and might have higher specificity. Chest radiography is less-resource intensive, is associated with lower radiation doses, is easier to repeat sequentially for monitoring disease progression or disease recovery, and can be performed with portable equipment at the point of care (which minimizes the risk of cross-infection related to patient transport).
 Chest CT has the highest sensitivity but relatively lower specificity and can be useful in patients with some pre-existing pulmonary diseases.
 Lung ultrasound has very low-certainty evidence supporting its diagnostic accuracy but might be helpful with the appropriate expertise as a supplemental or alternative modality (e.g. in pregnant women, children, patients with mechanical ventilation). Lung ultrasound can be done at the point of care but requires closer physical proximity of the operator to the patient for a longer period and needs specific infection prevention and control precautions.
 Consider the differential diagnoses and potential complications for each specific case (e.g. CT angiography for pulmonary arterial thrombosis or thromboembolism, ultrasound for pleural effusions and heart conditions) when choosing imaging modality.
 Choice should be made through shared decision-making involving the referring physician, the radiologist and the patient whenever possible. If possible, provide the patient with information regarding the imaging modality and the likelihood of subsequent imaging procedures.
Abbreviations: CT= computed tomography I n P r e s s . Implementation considerations that are common across recommendations.
 Implement the recommendations based on your equipment availability. Consider the resources needed (budget, health workforce, personal protective equipment, imaging equipment), the need to adapt the clinical workflow and the need to deprioritize other indications for imaging.
 When performing chest radiography, consider using portable equipment, and if feasible, a unit dedicated to patients with COVID-19.
 When performing chest radiography and chest CT, minimize radiation dose while maintaining diagnostic image quality (e.g. low-dose CT protocols) and use digital imaging rather than film-screen equipment .
 Consider the potential harm from exposure to ionizing radiation, in particular for pregnant women and children.
 Ensure proper use of personal protective equipment by health care workers and proper disinfection of equipment and devices (see Appendix E6).
 Provide appropriate training of radiologists and technologists on infection prevention and control practices and ensure efficient management of typical imaging findings of COVID-19 through accepted local protocols.
 Consider the transfer of images for remote reporting (teleradiology) as needed (e.g. settings where radiologists are not available for on-site reporting).
 Set policy/pathway for use of imaging related to COVID-19 illustrated with flow charts or diagrams locally developed and accepted.
I n P r e s s  Whenever is possible, provide information to patients about safety provisions adopted by the facility for infection prevention and control (see Appendix E6) as well as for radiation protection .
 Make provisions to ensure that all patients get the imaging services they need without suffering financial hardship. , as well as the Regional Advisor on Radiological Health in the WHO Regional Office for the Americas. The WHO steering group helped identify the GDG and external review group members. It contributed to the formulation of the key questions and reviewed the recommendations and the final document.

## Abbreviations

## Guideline development group
The GDG included experts and relevant stakeholders from multiple disciplines: a guideline methodologist, experts in the field of medical imaging, emergency medicine, intensive care, pulmonology and molecular diagnostics, as well as a representative from a patient advocacy organization. The GDG provided input at all stages of the process and played the main role in development of recommendations. The composition of the GDG ensured geographic representation from five of the six WHO regions, gender balance and absence of conflicts of interest.

## External review group
The external review group was composed of experts in the field of medical imaging and pulmonary diseases and representatives of patient advocacy groups and civil society. The experts reviewed the recommendations developed by the GDG and the final document, and commented on the technical accuracy, clarity of language, contextual issues and implications for implementation. The group was asked not to modify the recommendations that were formulated by the GDG.

## Systematic review team
The systematic review team was composed of experts in the field of systematic reviews with clinical background in internal medicine and content experts in the field of medical imaging. They conducted rapid reviews of the literature and provided a report summarizing the findings and certainty of evidence for each key question. The systematic review report was shared with members of the GDG. Representatives of the systematic review team attended the GDG meetings to provide an overview of the available evidence and to respond to technical queries from the GDG.

## Core group
The development of these recommendations under very compressed timelines during the COVID-19 pandemic represented a challenge in the context of unprecedented demands in terms of global and local public health response. Anticipating this challenge, the WHO Secretariat assembled a core group to assist in project management. This group included two methodologists, the chairperson of the GDG and a radiology consultant who worked in close consultation with the WHO Secretariat and participated in daily planning and coordination meetings held virtually. The core group drafted the key questions using the PICO format, supervised the syntheses and retrieval of evidence, convened and facilitated the GDG meetings, liaised with all established groups, and drafted and finalized the rapid advice guide. In addition, the core group facilitated survey implementation and assessment of current imaging practices in different regions of the world.

## List of contributors

## I n p r e s s

## Appendix e2: management of declaration of interests
The disclosure and appropriate management of relevant financial and non-financial conflicts of interest of guideline development group members and other external experts and contributors is a critical part of guideline development at WHO. According to WHO regulations, all experts must declare their interests prior to participation in WHO guideline development processes and meetings. All GDG members were therefore required to complete a standard WHO declaration of interests form before engaging in the guideline development process and before participating in guideline-related processes. All declarations were reviewed before finalizing the experts' invitations to participate based on the criteria for assessing the severity of conflict of interests as outlined in the WHO handbook for guideline development to all participating experts. All findings from the declaration of interests forms received were managed in accordance with the WHO declaration of interests guidelines on a case-by-case basis and communicated to the experts at the start of the first GDG meeting. Annex C shows a summary of the declaration of interests and how conflicts of interest declared by invited experts were managed.

## I n p r e s s

## Appendix e3: pico questions and critical outcomes identified pico questions identified
The following seven key PICO questions were identified:
1.
In asymptomatic contacts of patients with COVID-19, and in contexts where laboratory testing (reverse transcription-polymerase chain reaction [RT-PCR]) is not available/results are delayed/results are initially negative, should chest imaging (including chest radiography, CT scan, lung ultrasound) vs no chest imaging be used for the diagnostic workup of COVID-19? 2.
In symptomatic patients with suspected COVID-19, and in contexts where laboratory testing (RT-PCR) is not available/results are delayed/results are initially negative, should chest imaging (including chest radiography, CT scan, lung ultrasound) vs no chest imaging be used for the diagnostic workup of COVID-19? 3.
In patients with suspected or confirmed COVID-19, not currently hospitalized and with mild symptoms, should chest imaging (including chest radiography, CT scan, lung ultrasound) vs no chest imaging be used to support the decision on hospital admission versus home discharge? 4.
In patients with suspected or confirmed COVID-19, not currently hospitalized and exhibiting moderate to severe symptoms, should chest imaging (including chest radiography, CT scan, lung ultrasound) vs no chest imaging be used to support decision on regular ward admission versus ICU admission? 5.
In patients with suspected or confirmed COVID-19, currently hospitalized and exhibiting moderate or severe symptoms, should chest imaging (including chest radiography, CT scan, lung ultrasound) vs no chest imaging be used to modify the therapeutic management? 6.
In patients with suspected or confirmed COVID-19 and clinical deterioration and/or suspicion of pulmonary embolism, should imaging (including CT pulmonary angiography) vs no imaging be used to diagnose pulmonary embolism? 7.
In patients with COVID-19 whose symptoms are resolved, should chest imaging (including chest radiography, CT scan, lung ultrasound) be added to vs not added to laboratory criteria to support decisions on hospital discharge vs no discharge?

## Critical outcomes identified
The following critical outcomes were identified:
- diagnostic accuracy measures (rates of true positive, true negative, false positive, false negative); - clinical outcomes, including the "core outcomes" developed for COVID-19 (mortality, respiratory failure, multi-organ failure, shortness of breath, recovery), adverse effects of imaging (e.g. exposure to radiation), and COVID-19 transmission to health care workers;[1] - health systems outcomes, including service use (length of emergency department stay, length of hospital stay, length of ICU stay), availability of care, access to care and quality of care.

## I n p r e s s

# Conclusions

## Recommendation
For asymptomatic contacts of patients with COVID19, WHO suggests not using chest imaging for the diagnosis of COVID-19 (conditional recommendation, based on very low certainty evidence)

## Conditions:
 Higher risk of disease progression  In need of emergency procedures  implementing public health interventions (e.g., quarantine) I n P r e s s

## Remarks:
When choosing the imaging modality, consider the following:
 CT scan has the highest sensitivity and is preferred in patients with pre-existing pulmonary disease;  Chest radiography has a lower sensitivity but is associated with lower risk of HCW infection transmission; is less resource intensive; is associated with lower radiation doses than CT scan; and is easier to repeat sequentially for monitoring disease progression;
 LUS has limited evidence but is helpful with the appropriate expertise and can be done at the point of care. However, it requires closer physical proximity of the operator to the patient for a longer period of time and requires specific infection prevention and control precautions;
 Choice should consider the differential diagnosis in the specific case (e.g., CT angiography for pulmonary embolism, LUS for pleural effusions)  Choice should be through a shared decision making involving the patient, the referrer physician and the radiologist;
The voting results are: When PCR testing is not available, conditionally for using CT scan to diagnose COVID 19
 the rate of false-negative will be the lowest in low prevalence settings and in patients with low pretest probability (e.g., clinical presentation not consistent with COVID19)
 In patients who need to be admitted irrespective of diagnosis/likelihood of disease progression, to help with disposition (to dedicated COVID floor vs. non COVID floor)
Consider different alternatives e.g. chest radiography
The voting results are:
 Strong recommendation against the intervention: 0  Conditional recommendation against the intervention: 2  Conditional recommendation for either the intervention or the comparison: 0  Conditional recommendation for the intervention: 8  Strong recommendation for the intervention: 6
3-When PCR testing is available, but results are delayed, using vs. not using CT scan to diagnose COVID 19
When PCR testing is available, but results are delayed, conditionally for using CT scan to diagnose COVID 19  In patients requiring emergency procedures or other urgent interventions (e.g., in patients with stroke, requiring hemodialysis)  In patients who need to be admitted irrespective of diagnosis/likelihood of disease progression, to help with disposition (to dedicated COVID floor vs. non COVID floor)  In patients who need to be transferred to another facility
The voting results are:
 Strong recommendation against the intervention: 1  Conditional recommendation against the intervention: 3  Conditional recommendation for either the intervention or the comparison: 1  Conditional recommendation for the intervention: 8  Strong recommendation for the intervention: 1 I n P r e s s 4-In patients with negative initial PCR test, but with clinical suspicion of COVID19 (e.g., severe presentation or with co-morbidities), using vs. not using CT scan to diagnose COVID 19
In patients with negative initial PCR test, but with clinical suspicion of COVID19 (e.g., severe presentation or with co-morbidities), conditionally for using CT scan to diagnose COVID 19
The voting results are:
 Strong recommendation against the intervention: 0  Conditional recommendation against the intervention: 1  Conditional recommendation for either the intervention or the comparison: 1  Conditional recommendation for the intervention: 8  Strong recommendation for the intervention: 4

## Conditions (apply to 1 thru 4)
 Those who are discharged based on a negative CT scan result, need to consider a small chance of false-negative results and abide by public health measures (e.g., quarantine) until definitive PCR diagnosis is made  Resource use  Feasibility (PPE)  Acceptability (technicians)  Special attention to pregnant women and children  Apply appropriate clinical measures taking into account the possibility of false-negative results.
When choosing the imaging modality, consider the following:
 CT scan has the highest sensitivity and is preferred in patients with pre-existing pulmonary disease;  Chest radiography has a lower sensitivity but is associated with lower risk of HCW infection transmission; is less resource intensive; is associated with lower radiation doses than CT scan; and is easier to repeat sequentially for monitoring disease progression;  LUS has limited evidence but is helpful with the appropriate expertise and can be done at the point of care. However, it requires closer physical proximity of the operator to the patient for a longer period of time and requires specific infection prevention and control precautions;
 Choice should consider the differential diagnosis in the specific case (e.g., CT angiography for pulmonary embolism, LUS for pleural effusions)  Choice should be through a shared decision making involving the patient, the referrer physician and the radiologist;

## Remarks:
Patients likely to benefits are those who:
I n P r e s s  require emergency procedures or other urgent interventions (e.g., in patients with stroke, patients requiring hemodialysis);  need to be admitted irrespective of diagnosis (e.g., disease is severe or likely to progress), to help with disposition (to dedicated COVID19 floor vs. non COVID19 floor);  need to be transferred to another facility.  when using chest radiography and CT scan, optimize radiation dose, and use digital imaging rather than film (to decrease contamination).
**The voting was based on using CT scan vs not using CT scan, however the group decided that this applies to imaging vs no imaging.

## Justification

## Type of recommendation

## Strong recommendation against the intervention

## Conditional recommendation against the intervention
Conditional recommendation for either the intervention or the comparison

## Conditional recommendation for the intervention
Strong recommendation for the intervention    - 

# Conclusions recommendation
For patients with suspected or confirmed COVID-19, not currently hospitalized and with mild symptoms, WHO suggests using chest imaging to support the decision on hospital admission versus home discharge (conditional recommendation, based on very low certainty evidence)

## Remarks:
Patients likely to benefits are those who:
[formula]  [/formula]

# Conclusions recommendation
For patients with suspected or confirmed COVID-19, not currently hospitalized and with moderate to severe symptoms, WHO suggests using chest imaging to support the decision on regular ward admission versus intensive care unit admission (conditional recommendation, based on very low certainty evidence)

## Remarks:
Patients likely to benefits are those who:
 are at high risk of disease progression  are not responding to treatment When choosing the imaging modality, consider the following:
 CT scan has the highest sensitivity and is preferred in patients with pre-existing pulmonary disease;
I n P r e s s

## Research priorities
We identified some research priorities in areas where the certainty of the available evidence is low or very low, or where evidence is lacking. Those relevant to both diagnostic and management recommendations are:
- Conduct randomized controlled trials to compare the effects of using the different imaging modalities and using no imaging (in addition to clinical judgement) on clinical and health services outcomes of interest, for the questions addressed in this guidance.

# Introduction
Modifying working practices and training staff in the proper use of personal protective equipment and in the application of safe clinical imaging techniques, combined with environmental control and equipment disinfection are essential during the COVID-19 pandemic to reduce the risk of infection transmission to patients and staff. This focuses on the imaging modalities referred in the guide recommendations. Building upon WHO guidance on COVID-19 infection prevention and control in health care settings, this addresses good practices for infection prevention and control for front-line staff performing imaging procedures during the COVID-19 pandemic. Additionally, it describes specific infection prevention and control measures necessary while undertaking chest radiography both in the general imaging department and with portable radiography equipment, as well as when undertaking chest CT and lung ultrasound scans.

## General considerations
A checklist is provided on infection prevention and control when performing chest imaging in patients with suspected or confirmed COVID-19. Information inis applicable to all imaging modalities addressed.
In addition, it is important to remember that those undertaking imaging procedures are at the front line of the healthcare service, so they must follow existing local guidance/protocols. In general, the chest imaging procedures recommended in this guide require following droplet and contact precautions. Airborne precautions are reserved for aerosol-generating procedures (e.g. bronchoscopy, tracheotomy, cardiopulmonary resuscitation, non-invasive ventilation, intubation, nebulization, open suction). Below is a list of additional infection prevention and control considerations and best practices. General environment - Schedule appointments to reduce numbers of patients in the waiting room. Designate a waiting area, which should be set up to adopt international guidelines for social distancing of at least 1 metre minimally or whenever possible adapt to local or national guidelines (e.g. 2 metres is adopted in some settings - Ensure infection prevention and control measures are employed when managing the imaging room.
- The imaging room must be subject to regular cleaning and disinfection, consistent with local infection prevention and control guidance and cleaning schedules completed, signed and dated.
- Verify that terminal cleaning and disinfection of the imaging room occurred at end of day the previous day. If not done (or not verifiable) ensure that terminal cleaning and disinfection of the imaging room is performed before starting.

## During
- Ensure appropriate personal protective equipment worn.
- Employ " contact and noncontact radiographer/technologist" scenario of chest radiography, CT and ultrasound.
- Ensure single patient attendance to the imaging department wherever possible to enable further imaging, if this is required.
- Provide medical mask to the patient (if feasible), as well as comfort and reassurance.
- Ensure standard operating procedures for infection prevention and control according to local guidance, contact minimization and barrier precautions in place (e.g. suitable covers whenever possible).
- Control access to imaging room or patient area during the portable radiography procedure.
- Consider appropriate signage/visual alerts in front of imaging room (e.g. patient inside/arriving, ongoing cleaning/disinfection, time of last cleaning/disinfection).

## Post procedure
- Ensure imaging review is made appropriately and apply local protocols to follow up clinical and infection prevention and control actions, if/as required.
- If the chest imaging procedure was performed at the imaging department, staff should wear personal protective equipment during patient transfer.
- Ensure personal protective equipment is taken off appropriately, if used.
- Ensure rapid delivery of the imaging results to guide management.
- Ensure appropriate decontamination of medical equipment between patients (applicable to both fixed and portable equipment).
- Ensure appropriate environmental cleaning and disinfection (focus on high touch surfaces) between patients. Staff performing this task will be trained on cleaning and disinfection and should wear appropriate PPE.
- If bedside imaging was performed using portable equipment, room cleaning and disinfection should occur following the protocols applicable for the specific setting (e.g. emergency room, regular ward, intensive care unit)
- When performing CT on patients confirmed with COVID-19, radiographers/radiological technologists must follow the instructions and guidance of the hospital committee responsible for infectious disease control. - However asymptomatic patients pose a latent threat for medical imaging and therapy departments and hence radiographers/radiological technologists in CT are advised to follow the instructions divided in three stages (i.e. preparation, during and post procedure; see table 1).
Ultrasound:
- Lung ultrasound presents specific challenges. The first is physical proximity to the patient: this is usually within1 m and may be as little as 30-50cm; ultrasound rooms are typically small, ventilation may be restricted and seldom are there windows; examination time may last between 10 and 60 minutes; patients may be asked to inhale/exhale deeply and hold their breath. - If possible, designate a specific ultrasound room and machine and probes for use on patients with COVID-19. - Adjust schedule (appointment times) to avoid crowding in the waiting room and to allow time between appointments for decontamination of the ultrasound system and room. - 
Best practice is to have patient attend examination alone. - 
The ultrasound health care workers should follow droplet and contact precautions (airborne precautions required only for aerosol-generating procedures). They should use surgical/medical facemask. For any aerosol-generating procedures, an N95/FFP2/FFP3 medical protective mask or PAPR Powered Air Purifying respirators or respirators that offer a higher level of protection should be used. - 
The ultrasound health care workers should don personal protective equipment (including long sleeved gowns and gloves) when the patient is suspected or confirmed for COVID-19. - Shorten duration of examination by arranging for the most experienced professional available to perform the examination. Single use ultrasound gel sachets should be considered for patients suspected or having COVID-19. - Reduce the number of probes connected to the ultrasound machine to a minimum and remove all other probes from unit or store in closed cabinet to avoid the necessity of high-level disinfection in the event the patient coughs or sneezes during the procedure. - Separate inpatients on the ward from outpatients. - Cover the equipment such as the ultrasound scanner console to contribute to infection prevention and control and in this way enhance workflow. - Follow manufacturer's recommendation for decontamination of ultrasound system. - Follow local protocols for appropriate decontamination of ultrasound probes between patients. - Cleaning of probes includes three disinfection levels: non-critical, semi-critical and critical. Probes used for lung ultrasound would typically be in the first category, since they are usually in contact with intact skin (i.e. noncritical devices). However, all three levels are described below to cover any other possible scenario that would deserve a higher-level disinfection. - Noncritical devices: ultrasound probes that come in contact with intact skin can be cleaned and disinfected using low-or intermediate-level disinfection. - Semi-critical devices: ultrasound probes that come in contact with non-intact skin, blood, body fluids and/or mucous membranes should be cleaned and disinfected using the high level disinfection method. A single use probe cover is mandatory. - Critical devices: ultrasound probes must undergo sterilization if compatible or, if not available, high-level disinfection as per medical facility guidelines. Use of sterile transducer cover if mandatory.

## - 
In the context of COVID-19, the normal practices of high-level disinfection are not changed. The only change in the context of COVID-19 is that all external probes must undergo cleaning followed by low-level disinfection to denature any presence of SARS-CoV-2.