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      Managing high clinical suspicion COVID-19 inpatients with negative RT-PCR: a pragmatic and limited role for thoracic CT

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          As the COVID-19 pandemic sweeps across the UK there remain issues with reverse-transcription polymerase chain reaction (RT-PCR), the gold standard diagnostic method. Delays in obtaining results have been particularly problematic. Some patients, including those with high clinical suspicion of COVID-19, test falsely negative on initial RT-PCR test, sometimes requiring multiple subsequent tests to return an eventual positive result. Suggested possible reasons for this include: suboptimal clinical sampling techniques; variations in viral load; and manufacturer test kit sensitivity.1 With surging caseloads, managing these RT-PCR ‘negative’ patients is proving hugely challenging. An emerging bottleneck to effective care is dealing with isolation capacity. Inpatients who are truly PCR negative can be moved to a non-isolation ward, thereby freeing up isolation beds for COVID-19 positive patients and also reducing risk of nosocomial virus transmission. Patients with high index clinical suspicion of COVID-19, but who test negative on initial RT-PCR test, continue to be managed with respiratory isolation precautions, often undergoing repeat PCR testing. However, this means further delay while awaiting subsequent test results. Against this backdrop, an effective pathway to deal with negative COVID-19 RT-PCR results in the setting of high clinical probability is urgently needed. A further important concern is developing regarding deisolation on patient discharge to either home or community care: a confirmed COVID-19 diagnosis - or confirmed alternative, non-COVID-19 diagnosis - is key to imparting advice to families and carers. Imaging has been suggested as a potential solution to some of these problems. Most patients undergo chest radiograph (CXR) at presentation to hospital, with CXRs being hot-reported using a template classification system produced by British Society of Thoracic Imaging (BSTI).2 This stratifies patients into one of four groups based on CXR: COVID classic/probable; COVID indeterminate; COVID normal; and Non-COVID. Frontline doctors have found this a useful adjunct to clinical assessment. In mainland China, CT was often a first-line investigation for COVID-19. However, such practice was burdensome on radiology departments and hugely challenging for infection control. CT in COVID-19 shows typical findings of ground glass opacity, peripheral consolidation or a combination of both. Ai et al reported CT sensitivity from their Wuhan cohort of 97% when compared with RT-PCR.3 When combined with the possibility for near instantaneous results, it is perhaps not surprising that CT has seen most widespread use in endemic regions of China, Italy and Iran. Some reports have also described typical CT findings consistent with COVID-19 in patients with initial negative RT-PCR who subsequently tested positive on repeat RT-PCR testing.3 4 Several authors5 and professional societies6 have steadfastly suggested that CT should not be used as a first line or pure diagnostic test – while highly sensitive, CT findings of COVID-19 pneumonia are not specific. In addition, false negative CT rates vary in the literature, ranging from 3%–56% in RT-PCR positive patients.7 CT features tend to peak later (day 6–11) in the disease course.8 Importantly, there are huge resource implications of this approach as the scanner requires decontamination each time a ‘positive’ patient is scanned. Radiographers risk repeated exposures to COVID-19, with high likelihood of illness and absence from work, at a time when healthcare workers are a precious resource. Finally, concerning reports from Italy suggest that over-reliance on CT potentially contributed to ‘dirty’ scanners acting as virus transmission vectors, thereby exacerbating COVID-19 spread among staff and COVID-19 naive patients. We agree with Hope et al 5 that “…CT does not add diagnostic value” if used indiscriminately but would disagree that it has no role to play in diagnostic workup. They state “it is clear that the positive results can only be believed if the pre-test probability of disease is high.” This is supported by data from Wong et al where “in the scenario of high clinical suspicion of COVID-19 it is conceivable that a positive CXR can obviate the need for a CT”, thereby reducing burden on CT units during the COVID-19 pandemic.9 While awaiting the RT-PCR result, most suspected COVID-19 patients are clinically diagnosed with the triad of clinical assessment, CXR and blood tests. CT could however play a limited, but important, role in providing diagnostic radiological confirmation in patients with clinically suspected - but RT-PCR negative - disease. This would potentially help resolve whether a patient with suspected high clinical probability of COVID-19 has an alternative diagnosis in addition to influencing infection control strategy (namely the ability to stepdown a patient to a deisolation ward). We have seen patients with negative RT-PCR at presentation with ‘classic/probable’2 changes on CXR and repeat RT-PCR which returns positive. However, there remain a small proportion of patients in whom multiple RT-PCRs are negative and whose CXRs are repeatedly ‘normal’ or ‘indeterminate’, although clinical suspicion remains high. These ‘high clinical probability’ patients are those unwell enough to be admitted to hospital and are not presumed to represent the complete spectrum of COVID-19 patients, most of whom have mild symptoms requiring self-isolation in the community. Our institution has thus devised a pragmatic protocol (figure 1), using CT to help diagnose this group of patients. Capacity for CT use in this limited way has been created as a result of cancelling elective/routine CT requests for other indications, thereby permitting not only rapid access to CT scanning but also allowing ample time for scanner terminal clean in between cases. In our algorithm, CT is performed in patients who return two negative RT-PCR swabs and two CXRs (≥48 hours apart) reported as ‘normal’ or ‘indeterminate’ for COVID-19 (‘double-double negative’). RT-PCR remains the lynchpin of diagnosis and, if negative, is repeated (usually around 48 hours after presentation). The rationale for repeat CXR in patients where the index CXR was not COVID-19 classic/probable is that several patients go on to develop COVID classic appearances, despite a normal/indeterminate index CXR, in the setting of high clinical probability. Figure 1 Proposed infection control management of inpatients with a negative initial COVID-19 nose/throat swab RT-PCR. Patients who are deemed eligible for CT as per our protocol undergo a sequential low dose non-contrast CT thorax and CT pulmonary angiogram (if renal function allows).10 CTPA is performed to ensure occult PE is excluded, particularly in light of reports of increased pro-thrombotic risk in COVID-19. The non-contrast CT prior is performed for two main reasons: i) dependent ground glass is often exaggerated on post-contrast scan and can be mistaken for true ground glass; ii) having a baseline non-contrast scan can be useful if then performing subsequent unenhanced scans. The key to our pathway is thorough clinical assessment as pre-test probability determines how these patients are managed, above all else. As the pandemic progresses it may be that so many cases ‘swamp’ the system that CT is forced to take a more upfront role in patient triage. At present with infection control such a key facet of patient management – as well as staff safety – the RFL NHS Trust negative PCR pathway enables a systematic approach to patient deisolation and stepdown from COVID ward to Non-COVID wards.

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          Patients with RT-PCR-confirmed COVID-19 and Normal Chest CT

          Editor: We read with great interest the recently published articles on Coronavirus Disease 2019 (COVID-19) in Radiology. Thanks to the journal for the rapid and efficient efforts, which is helping medical staff members and radiologists around the world improve their understanding of this disease. CT can play a vital role in the early detection and management of COVID-19 (1,2). However, it is worth emphasizing that a patient with reverse-transcription polymerase chain reaction (RT-PCR)-confirmed COVID-19 infection may have normal chest CT at admission. Bernheim et al (3) reported 20 (56%) of 36 patients imaged 0–2 days after symptom onset had normal CT. Fang et al (4) reported one of 51 (2%) patient imaged 3 days ± 3 after symptom onset with normal CT. Ai et al reported (5) 21 of 601 (3%) RT-PCR-positive patients with clinical symptoms had normal CT scans. In contrast, Pan et al (6) reported four of 21 (19%) patients with first normal CT had lung abnormalities on the follow-up CT approximately 4 days later. In our experience (7), among 17 of 149 (11.4%) symptomatic patients with normal chest CT on admission, 12 remained negative 10 days later with two to three follow-up CT examinations and the chest CT of the other five patients became positive over an average of 7 days. These reports confirm that a normal chest CT scan cannot exclude the diagnosis of COVID-19, especially for patients with early onset of symptoms. At present, RT-PCR test remains the reference standard to make a definitive diagnosis of COVID-19 infection despite the false-negative rate. In the fifth edition of the Diagnosis and Treatment Program of 2019 New Coronavirus Pneumonia proposed by The National Health Commission of China (8), chest CT findings were included as evidence of clinical diagnosis of COVID-19 for patients in Hubei province. However, chest CT findings were removed from diagnostic criteria in the most recently published sixth version (9). The final etiology diagnosis of COVID-19 should be confirmed by positive RT-PCR or gene sequencing. The early diagnosis of COVID-19 is critical for prevention and control of this pandemic. Clinicians should be vigilant at all times to identify patients with COVID-19 infection, who may have few or no clinical symptoms, normal chest CT, and or even initial negative PR-PCT test.
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            A British Society of Thoracic Imaging statement: considerations in designing local imaging diagnostic algorithms for the COVID-19 pandemic

            Introduction In accordance with guidance from the Chief Medical Officer's office and the Royal College of Radiologists, the British Society of Thoracic Imaging (BSTI) recognises that based on the available evidence computed tomography (CT) currently has no upfront role in the diagnostic work-up of 2019 novel coronavirus (COVID-19) infection (https://www.rcr.ac.uk/college/coronavirus-covid-19-what-rcr-doing/rcr-position-role-ct-patients-suspected-covid-19). Nevertheless, a number of reports have been published highlighting CT appearances in COVID-19, raising the possibility of a role for CT in patient management.1, 2, 3, 4, 5 In response to these reports, the BSTI published a preliminary consensus statement on 6 March 2020. 6 We discuss below what role, if any, CT would play in the detection and management of COVID-19 infection in the UK, and the logistics of imaging delivery. This role is heavily predicated on the clinical context as well as the timing of its intended use within the diagnostic pathway, especially relative to the current reference standard diagnostic test, real-time reverse transcriptase polymerase chain reaction (RT-PCR) of a pharyngeal swab, 7 and other clinical and laboratory investigations. Although it may not be feasible or desirable for isolation purposes to perform a chest radiograph (CXR), we should acknowledge that pragmatically patients with a respiratory complaint are likely to present via any number of routes (primary care, emergency departments [EDs] or outpatient clinics) having already had a CXR, other than to isolation pods outside a hospital, and work-up of a respiratory complaint would usually include a CXR in such settings. Cognizant of this fact, in the following discussion we have considered how a CXR would also fit into diagnostic algorithms, and in particular, how the use of CT would alter management in settings where a CXR was or was not available. As such, we deliberate the following questions: (1) would a CT thorax contribute to management of symptomatic cases after a rapidly available RT-PCR result? (2) Would a CT thorax contribute to symptomatic cases if an RT-PCR test was not available or had to be rationed, and (a) a chest radiograph had been performed and was abnormal? (b) A chest radiograph had been performed and was normal, or was not/could not be performed? (3) Would a CT thorax contribute to the detection and management of COVID-19 in asymptomatic high-risk cases? (4) How should imaging (CT thorax or CXR) be provided? (5) What would a COVID-19 diagnostic algorithm look like? In the following discussion, a high pre-test probability is assumed for symptomatic cases, based on one or more of: clinical presentation (Pyrexia of 37.8); acute onset persistent cough, hoarseness, nasal discharge or congestion, shortness of breath, sore throat, wheezing, sneezing; and compatible laboratory abnormalities (relative lymphopenia, elevated C-reactive protein [CRP]). 8 Question 1: Would a CT thorax contribute to patient diagnosis after a rapidly available RT-PCR result? If the RT-PCR result is positive CT findings in this setting would not change diagnosis and may be falsely negative in about 2–3% of RT-PCR positive symptomatic cases. 2 , 5 As such, we do not envisage a role for CT in this setting. If the RT-PCR result is negative In this setting, the role of CT is less certain. RT-PCR has a reported sensitivity of 60–70% 2 , 5 and thus approximately 30–40% of patients with COVID-19 infection could initially have a false-negative result. False-negative results may arise for a number of reasons including inadequate sampling technique or low viral load and thus many patients will require multiple testing to exclude the diagnosis. Ai et al. found that of 64 patients with initially negative RT-PCR testing, 15/64 (23.4%) had subsequent positive RT-PCR (mean time interval 5.1±0.5 days). Ten of these patients (i.e., only 15.6% of those with initial negative RT-PCR) had typical features on CT at the time of initial negative RT-PCR. 5 Fang et al. described a 29.4% rate of CT abnormality in patients with initially negative and subsequently positive RT-PCR. 2 As such, in the minority of patients with high clinical suspicion but negative initial RT-PCR, the presence of typical CT appearances, such as peripheral ground-glass opacity, could be used to rapidly diagnose COVID-19 infection, until such time as multiple negative testing is sufficient to exclude or change the diagnosis. Conversely, it is important to note that a normal CT cannot be used to exclude a diagnosis of COVID-19 when duration of symptoms is short, 9 although there is some evidence to suggest that the negative predictive value of CT is higher when symptom duration is >1 week. 10 , 11 Nevertheless, even in this scenario, multiple PCR testing should be the preferred method to exclude the diagnosis if no limitation on PCR testing (both availability and turn around times) exists. Some CT characteristics, such as pleural effusion, lymphadenopathy, and tree-in-bud nodularity, have been reported as uncommon in COVID-19 and the presence of these features should prompt for evaluation of alternative diagnoses. Therefore, we regard the role of CT in COVID-19 confirmed cases following RT-PCR results to be the same as in any other viral infection, in that it could be used to: (1) find co-existing or underlying diagnoses; (2) help diagnose complications, or investigate a clinically discordant picture (e.g., CRP decline, but increasing hypoxia); and (3) add value in patients with pre-existing lung diseases. Even if CT is used to aid rapid diagnosis, it needs to be made clear how this would translate into a change in management. A practical strategy for patients with initially negative RT-PCR could involve triage into the following categories: (1) self-isolation at home for those with no CT abnormality, with serial testing later to definitively exclude the diagnosis; (2) self-isolation or hospital isolation (depending on clinical status) for patients with typical CT appearances; and (3) urgent evaluation for alternative diagnoses, while still maintaining isolation, for patients with non-typical CT abnormalities. It certainly could be argued, however, that a combination of clinical, laboratory and CXR findings could also be used to triage patients with suspected COVID-19 requiring hospital admission in the first instance, reserving CT for challenging situations. The relative proportions of patients in each triage category would probably differ, given the increased sensitivity of CT for COVID-19, but we are unaware of any data comparing the sensitivity of CT to a combination of CXR and laboratory findings to shed any further light on the relative merits of these different strategies. A study by Xiong et al. offers a compelling argument for such a strategy: in their analysis of 42 patients, clinical findings and white blood cell count were not well-correlated with initial CT findings, but CRP, erythrocyte sedimentation rate (ESR), and serum lactate dehydrogenase (LDH) were significantly moderately to strongly correlated with the extent and severity of overall involvement and the size of the largest CT lesion. 10 The use of CT as the main diagnostic tool for COVID-19 over and above RT-PCR in China has been subsequently challenged. 12 It is noteworthy that the fifth edition of the Diagnosis and Treatment Program of 2019 New Coronavirus Pneumonia proposed by The National Health Commission of China included chest CT findings as a diagnostic criterion, 13 but CT was removed in the more recent sixth and seventh versions, 14 , 15 reflecting the extremely dynamic nature of consensus opinion on this subject. Question 2: Would a CT thorax contribute to symptomatic cases if an RT-PCR test was not available or had to be rationed? A limited or exhausted supply of RT-PCR testing kits is not inconceivable. Even if a robust supply was in place, other factors, such as interruption of transport infrastructure and availability of sufficient virology capacity, or the limited number of centres that could process results, could impede the utility of this test. We consider the following two scenarios. If a chest radiograph had been performed and was abnormal It is salutary that CXR may be abnormal in the majority of COVID-19 cases, especially severe cases, 16 , 17 with severity defined according to standard definitions. 18 Huang et al. found bilateral radiographic abnormalities in 40/41 (98%) of cases 16 ; Guan et al. found radiographic abnormalities in 162/274 patients (59.1%), but CXR was more likely to be abnormal in severe disease (46/60 [76.7%] with severe disease, versus 116/214 [54.2%] of non-severe disease). 17 Conversely, CT thorax has a very low specificity, approximately 25%, for COVID-195. Furthermore, CRP is abnormally elevated in between 61% to 92% of patients. 17 , 19 As such, we do not consider a CT thorax to provide additive benefit to diagnosis over and above high clinical suspicion, laboratory findings, and typical radiographic abnormalities in this setting. Further work is needed to understand the potential role of CT in providing prognostic information, in particular in patients with severe disease, including guiding management of patients recovering from severe disease. If a chest radiograph had been performed and was normal, or was not/could not be performed In this setting, the lack of initial RT-PCR testing availability could necessitate an alternative test. A CT thorax could then be viewed as the optimum initial diagnostic tool for all the reasons discussed in Question 1. Assuming it becomes necessary to elevate CT thorax to this position in the diagnostic work-up, the role of CT thorax in guiding management would be to triage patients into the categories discussed earlier (self-isolation at home with repeat testing as necessary, admission and isolation, or evaluation for alternative diagnoses and potentially aiding triage of unwell patients). In Table 1 , we illustrate the possible use of CT as a triage mechanism prior to initial RT-PCR results being available. For all scenarios, we have further assumed that, regardless of the presence or absence of initial radiographic abnormalities, initial management would necessitate isolation and standard care given high clinical suspicion. Furthermore, if a chest radiograph suggests an alternative diagnosis (such as lobar pneumonia), the CT may provide no additional pragmatic benefit over and above clinical suspicion and RT-PCR results, and as such, we do not consider it beneficial to explore the permutations of that scenario. Table 1 Possible impact of computed tomography (CT) on the diagnosis of COVID-19, assuming no RT-PCR result is available initially. Table 1 Scenario no. CT findings for COVID-19 CT-based triage categorya Initial RT-PCR result Would a rapidly available RT-PCR have voided the CT result? Management post-initial RT-PCR result Repeat RT-PCR result (if obtained)(4–10 days) Management following repeat RT-PCR result 1 Typical Isolation ± admission Positive Yesb Unchanged Positive Unchanged 2 Typical Isolation ± admission Positive Yesb Unchanged Negative Unchanged: in this subgroup, 60% of cases show imaging features prior or parallel to RT-PCR positivity, and the subsequent negative RT-PCR does not decrease clinical probability of COVID-19 infection; however, the role of CT in evaluating response in conjunction with RT-PCR requires further work 3 Typical Isolation ± admission Negative Noc Unchanged Positive Unchanged: 16–29% of patients with initial negative RT-PCR could have positive typical CT findings. 4 Typical Isolation ± admission Negative No Downgrade to self-isolation depending on clinical status, await repeat RT-PCR Negative Possible downgrade: may be considered COVID-19 negative. Repeat CT in this scenario may also have a role in guiding management along with clinical evaluation. 5 Clear Self-isolation, do not admit Positive Yesb Possible upgrade to admission depending on clinical status. Negative CT may indicate non-severe disease. Whether this independently impacts prognosis requires further work Positive Unchanged 6 Clear Self-isolation, do not admit Positive Yesb Possible upgrade to admission depending on clinical status. Whether this independently impacts prognosis requires further work Negative Unchanged: RT-PCR results would be guiding management here, and a negative follow-up RT-PCR result does not exclude COVID-19 infection; however, the role of CT in evaluating response in conjunction with RT-PCR requires further work 7 Clear Self-isolation, do not admit Negative Noc Unchanged Positive Possible upgrade: depending on symptom duration, initial CT could be negative 8 Clear Self-isolation, do not admit Negative Yesb Unchanged Negative Possible downgrade: may be considered COVID-19 negative. In some clinical scenarios, CT may have a role in determining the frequency and prioritisation of repeat testing, and the level of cohort isolation required, all of which requires further consensus. a The decision to admit will be based on clinical and laboratory parameters. b CT demonstration of underlying lung disease or alternative diagnosis could still be useful. c RT-PCR would be false-negative in this scenario. Question 3: Would a CT thorax contribute to the detection and management of COVID-19 in asymptomatic high-risk cases? Data on the prevalence of CT abnormalities, and thus the accuracy of CT, in detecting COVID-19 in asymptomatic contacts of positive or confirmed cases are scarce. At the time of writing, we are aware of only two publications on the subject. Hu et al. 20 evaluated the laboratory and CT characteristics of 24 asymptomatic close contacts who were COVID-19 carriers, as confirmed by RT-PCR. Seventeen of 24 (70.8%) had CT abnormalities, with 12 (50% of total) showing typical peripheral ground-glass opacity. The minority had lymphopenia (16.8%) and elevated CRP (17.4%). The 17 patients with CT abnormalities were older (median age 38 versus 14 years old, p=0.012). A more recent analysis by Inui et al of 112 RT-PCR confirmed cases of COVID-19 from the cruise ship “Diamond Princess” demonstrated CT abnormalities in only 44/82 (54%) asymptomatic cases (reference https://doi.org/10.1148/ryct.2020200110). In combination, this reinforces the unsuitability of CT in isolation as a screening tool for this subgroup. Even if CT were to be used to screen close contacts, we cannot envisage the practical value of such a strategy, compared to serial RT-PCR testing (as long as the latter is available), given that such contacts would be advised to self-isolate. In addition, the specificity of CT or RT-PCR for screening asymptomatic contacts in this manner is undefined. Question 4: HOW should imaging (CT thorax or chest radiography) be provided? Inevitably, the provision of imaging will depend on local protocols for isolation and identification of suspected COVID-19 patients when they first present; however, we consider the following broad options. Regardless of the option, the need to perform a comprehensive clean of equipment between patients (to protect negative patients from positive ones), and the implications that has for throughput, should be recognised. Mobile CXR unit alongside dedicated COVID-19 assessment area located outside the main hospital building A mobile unit set up in this way would be able to maintain high throughput and fast image transfer and interpretation. Such a strategy may, with the agreement of local respiratory and infectious diseases teams, even obviate the need for CT thorax, but only if (a) RT-PCR testing and results are available rapidly; and (b) there is still an intention to isolate and treat patients with negative CXR and RT-PCR but high pre-test probability. Mobile CT scanner unit alongside dedicated COVID-19 assessment area located outside the main hospital building A CT unit set up in this way would also allow high throughput, as the type of CT required for diagnosis is easy and rapid to perform (unenhanced thoracic CT). Image transfer and interpretation would take longer relative to CXR, but rapid reporting turnaround could be aided by structured reporting templates for relevant abnormalities only. Examples of such templates are provided on the BSTI website at bsti.org.uk. Such a CT set-up realistically obviates the need for mobile CXR provision. Mobile CT scanner in a community location It may be desirable to locate CT scanners in community locations away from the hospital or take advantage of existing community-located scanners. Adequate operating procedures to ensure rapid transmission of images to designated reporting centres would be required in such cases. ED CT/CXR for COVID-19 patients, mobile CT/CXR for routine ED imaging As patients with COVID-19 may bypass the dedicated assessment area and present to ED itself, this strategy would allow imaging to be performed without potentiating transmission to other ED attendees via the scanner. Regular ED work could be transferred to mobile scanners alongside the ED; however, such a strategy would not obviate the need for local cleaning procedures. In addition, logistically, such a set-up would be challenging due to default image transfer protocols and worklist interactions between ED scanners, radiology information systems (RIS) and picture archiving and communications systems (PACS). Fixed site non-ED CT scanner For trusts where CT scanner(s) are solely based within the radiology department contingency plans for “scanner downtime” during deep cleans and policies to minimise cross-contamination would need to be instigated. An alternative would be for trusts to consider a mobile CT scanner unit outside the hospital; however, for inpatients with suspected or confirmed COVID-19 infection who require further imaging, such as CT pulmonary angiography, or for very unwell patients, a fixed site ED or non-ED CT scanner would be the only options. In this circumstance, it may be pragmatic to ring-fence consecutive slots for the confirmed COVID-19 cases on the nominated scanner to make cleaning more practical. Question 5: What would a COVID-19 diagnostic algorithm look like Figure 1 illustrates the diagnostic work-up algorithm now endorsed by the British Society of Thoracic Imaging, Dr Cliff Mann, National Clinical Director of Urgent and Emergency Care, Dr Matt Inada-Kim, National Clinical Advisor in Sepsis and Deterioration, and Professor Erika Denton, National Clinical Director for Diagnostics. The algorithm consolidates the foregoing discussion on the role of imaging by (1) placing clinical and laboratory assessment, and the patient's clinical condition, at its centre; (2) using CXR as the initial diagnostic imaging tool; and (3) suggesting a potential role for CT in cases with a normal or indeterminate CXR. Figure 1 BSTI/NHSE Radiology decision tool for suspected COVID-19 (available at https://www.bsti.org.uk/standards-clinical-guidelines/clinical-guidelines/bsti-nhse-covid-19-radiology-decision-support-tool/). Figure 1 Conclusion The putative role of CT in the diagnosis, triage, and prognostication of patients with COVID-19 infection continues to be refined. We explore scenarios integrating CT into the diagnostic algorithm; however, the clinical value of this integration, compared to alternative strategies incorporating quick and immediately scalable standard clinical and laboratory assessment (even in the absence of RT-PCR availability) is unknown, because published studies on thoracic CT in COVID-19 infection to date have, frustratingly, described these assessments without analysing their relative merit as part of an alternative diagnostic strategy. In the absence of such data, we can only reiterate the need for strategic thinking that explores all available options to achieve maximum public benefit, optimise throughput in the shortest timeframe, and minimise detriment. Declaration of Competing Interest The authors declare no conflict of interest.
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              Correspondence a role for CT in really tell us so far

               M Hope,  C Raptis,  A Shah (2020)

                Author and article information

                BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )
                July 2020
                21 April 2020
                21 April 2020
                : 75
                : 7
                : 537-538
                [1 ] departmentDepartment of Radiology , Royal Free London NHS Foundation Trust , London, UK
                [2 ] departmentDepartment of Respiratory Medicine , Royal Free London NHS FoundationTrust , London, UK
                [3 ] departmentDepartment of Microbiology , Royal Free London NHS Foundation Trust , London, UK
                Author notes
                [Correspondence to ] Dr Samanjit S Hare, Department of Radiology, Royal Free London NHS Foundation Trust, London, United Kingdom; samhare@ 123456nhs.net

                ANT and AB are joint first authors.

                DDC and SSH are joint senior authors.

                © Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.

                This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

                Controversies and Challenges in Respiratory Medicine
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