Accuracy of Low-Dose Chest CT Scan in Detection of COVID-19
2020; Radiological Society of North America; Volume: 2; Issue: 3 Linguagem: Inglês
10.1148/ryct.2020200256
ISSN2638-6135
AutoresHooman Bahrami‐Motlagh, Morteza Sanei Taheri, Sahar Abbasi, Maryam Haghighi-Morad, Babak Salevatipour, Ilad Alavi Darazam,
Tópico(s)COVID-19 Clinical Research Studies
ResumoHomeRadiology: Cardiothoracic ImagingVol. 2, No. 3 PreviousNext Letters to the EditorFree AccessAccuracy of Low-Dose Chest CT Scan in Detection of COVID-19Hooman Bahrami-Motlagh, Morteza Sanei Taheri, Sahar Abbasi, Maryam Haghighi-Morad, Babak Salevatipour, Ilad Alavi DarazamHooman Bahrami-Motlagh, Morteza Sanei Taheri, Sahar Abbasi, Maryam Haghighi-Morad, Babak Salevatipour, Ilad Alavi DarazamAuthor AffiliationsDepartment of Radiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Loghman Hakim Hospital, Tehran 1333625445, Islamic Republic of Irane-mail: [email protected]Hooman Bahrami-MotlaghMorteza Sanei TaheriSahar AbbasiMaryam Haghighi-MoradBabak SalevatipourIlad Alavi DarazamPublished Online:May 27 2020https://doi.org/10.1148/ryct.2020200256MoreSectionsPDF ToolsAdd to favoritesCiteTrack Citations ShareShare onFacebookXLinked In Editor:We read the informative article by Dr Dangis and colleagues in the April 2020 issue of Radiology: Cardiothoracic Imaging about the accuracy of low-dose chest CT in the diagnosis of coronavirus disease 2019 (COVID-19) (1). Considering that in many settings chest CT scan is used widely for detection of COVID-19 pneumonia, using a low-dose protocol especially in patients younger than 40 years is important. This interesting study reported accuracy of 90.2% in all patients and 94.4% in the subset of patients with chest CT performed 48 hours after symptom onset. The sensitivity and specificity values were respectively 86.7% and 93.6%, while in a recent meta-analysis including 63 studies, Kim et al (2) reported combined sensitivity and specificity of chest CT for the diagnosis of COVID-19, considering polymerase chain reaction test as the reference standard, as 94% and 37%, respectively. Pooled prevalence of COVID-19 mainly from reports in China is about 39%, which is near to what Dr Dangis and colleagues (1) report with described pretest probability of 43.2%. Additionally, we have conducted a study in Tehran, Iran utilizing low-dose chest CT on 163 patients and observed a sensitivity value of 96.6% (95% CI: 90%, 99%) and specificity value of 36.5% (95% CI: 26%, 49%) (unpublished results), which is more compatible with the numbers in the mentioned meta-analysis. Although Dr Dangis and colleagues (1) stated that a potential reason for their high specificity was the repeated reverse-transcription polymerase chain reaction (RT-PCR) test after 24 hours in cases with initial negative RT-PCR result, the specificity of standard-dose CT scan in four previous studies with repeated RT-PCR have ranged between 25% and 56% (3–6). It seems that other explanations for the observed high specificity of low-dose chest CT should be explored. Additionally, the specificity of low-dose CT scan for a subset of patients with initial negative RT-PCR results are not reported separately in their study.In conclusion, this remarkable study by Dr Dangis and colleagues (1) demonstrates excellent accuracy of low-dose chest CT in the diagnosis of COVID-19 pneumonia, with exceptional high specificity compared with previous standard-dose studies, which remains to be further validated.Disclosures of Conflicts of Interest: H.B.M. disclosed no relevant relationships. M.S.T. disclosed no relevant relationships. S.A. disclosed no relevant relationships. M.H.M. disclosed no relevant relationships. B.S. disclosed no relevant relationships. I.A.D. disclosed no relevant relationships.References1. Dangis A, Gieraerts C, Bruecker YD, et al. Accuracy and reproducibility of low-dose submillisievert chest CT for the diagnosis of COVID-19. Radiol Cardiothorac Imaging 2020;2(2):e200196. Link, Google Scholar2. Kim H, Hong H, Yoon SH. Diagnostic Performance of CT and Reverse Transcriptase-Polymerase Chain Reaction for Coronavirus Disease 2019: A Meta-Analysis. Radiology 2020 Apr 17:201343 [Epub ahead of print] Link, Google Scholar3. Ai T, Yang Z, Hou H, et al. Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases. Radiology 2020 Feb 26:200642 [Epub ahead of print] Link, Google Scholar4. Zhu W, Xie K, Lu H, Xu L, Zhou S, Fang S. Initial clinical features of suspected coronavirus disease 2019 in two emergency departments outside of Hubei, China. J Med Virol 2020 Mar 13 [Epub ahead of print] Crossref, Google Scholar5. Cheng Z, Lu Y, Cao Q, et al. Clinical features and chest CT manifestations of coronavirus disease 2019 (COVID-19) in a single-center study in Shanghai, China. AJR Am J Roentgenol 2020 Mar 14:1–6 [Epub ahead of print] Crossref, Google Scholar6. Caruso D, Zerunian M, Polici M, et al. Chest CT Features of COVID-19 in Rome, Italy. Radiology 2020 Apr 3:201237 [Epub ahead of print] Link, Google ScholarReferences1. Dangis A, Gieraerts C, De Bruecker Y, et al. Accuracy and reproducibility of low-dose submillisievert chest CT for the diagnosis of COVID-19. Radiol Cardiothorac Imaging 2020;2(2):e200196. Link, Google Scholar2. Ai T, Yang Z, Hou H, et al. Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases. Radiology 2020 Feb 26:200642 [Epub ahead of print] Link, Google Scholar3. Kim H, Hong H, Yoon SH. Diagnostic Performance of CT and Reverse Transcriptase-Polymerase Chain Reaction for Coronavirus Disease 2019: A Meta-Analysis. Radiology 2020 Apr 17:201343 [Epub ahead of print] Link, Google Scholar4. Caruso D, Zerunian .M, Polici M, et al. Chest CT Features of COVID-19 in Rome, Italy. Radiology 2020 Apr 3:201237 [Epub ahead of print] Link, Google Scholar5. Bai HX, Hsieh B, Xiong Z, et al. Performance of Radiologists in Differentiating COVID-19 From Viral Pneumonia on Chest CT. Radiology 2020 Mar 10:200823 [Epub ahead of print]. Link, Google Scholar6. Symons R, Pourmorteza A, Sandfort V, et al. Feasibility of Dose-reduced Chest CT with Photon-counting Detectors: Initial Results in Humans. Radiology 2017;285(3):980–989. Link, Google ScholarReferences1. Dangis A, Gieraerts C, Bruecker YD, et al. Accuracy and reproducibility of low-dose submillisievert chest CT for the diagnosis of COVID-19. Radiol Cardiothorac Imaging 2020;2(2):e200196. Link, Google Scholar2. Kim H, Hong H, Yoon SH. Diagnostic Performance of CT and Reverse Transcriptase-Polymerase Chain Reaction for Coronavirus Disease 2019: A Meta-Analysis. Radiology 2020 Apr 17:201343 [Epub ahead of print] Link, Google Scholar3. Ai T, Yang Z, Hou H, et al. Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases. Radiology 2020 Feb 26:200642 [Epub ahead of print] Link, Google Scholar4. Zhu W, Xie K, Lu H, Xu L, Zhou S, Fang S. Initial clinical features of suspected coronavirus disease 2019 in two emergency departments outside of Hubei, China. J Med Virol 2020 Mar 13 [Epub ahead of print] Crossref, Google Scholar5. Cheng Z, Lu Y, Cao Q, et al. Clinical features and chest CT manifestations of coronavirus disease 2019 (COVID-19) in a single-center study in Shanghai, China. AJR Am J Roentgenol 2020 Mar 14:1–6 [Epub ahead of print] Crossref, Google Scholar6. Caruso D, Zerunian M, Polici M, et al. Chest CT Features of COVID-19 in Rome, Italy. Radiology 2020 Apr 3:201237 [Epub ahead of print] Link, Google ScholarResponseAnthony Dangis*, Christopher Gieraerts*, Yves De Bruecker*, Lode Janssen*, Hanne Valgaeren†, Dagmar Obbels†, Marc Gillis‡, Marc Van Ranst§, Johan Frans†, Annick Demeyere*, Rolf Symons* Anthony Dangis*, Christopher Gieraerts*, Yves De Bruecker*, Lode Janssen*, Hanne Valgaeren†, Dagmar Obbels†, Marc Gillis‡, Marc Van Ranst§, Johan Frans†, Annick Demeyere*, Rolf Symons* Author AffiliationsDepartments of Radiology*Microbiology,† andEmergency Medicine,‡ Imelda Hospital, Imeldalaan 9, 2820 Bonheiden, BelgiumDepartment of Microbiology, University Hospital Leuven, Leuven, Belgium§e-mail: [email protected]We thank the authors for their interest in our article (1). The plethora of research articles on COVID-19 may tempt us to directly compare studies or translate results to our own daily routine. It is important, however, to realize that measurements of diagnostic accuracy such as sensitivity and specificity are only valid for the study population from which they are obtained and for the reference test against which they are compared.First, the use of low-sensitivity RT-PCR reference tests in early studies from China leads to an underestimation of CT specificity and is directly mentioned by Tao et al in their study limitations (2). As the vast majority of studies in the meta-analysis by Kim et al originate from China, their likely use of low-sensitivity RT-PCR assays explains the observed low specificity (3). Caruso et al from Italy do not directly mention the sensitivity of their RT-PCR assay, but as this study included 96 RT-PCR negative patients, of which 42 had positive findings on chest CT, it is very likely that part of these "false positives" on CT were in fact true positives (4). In a reader study eliminating effects of an imperfect reference test, Bai et al reported specificity of 93%–100%, similar to our results (5). Our RT-PCR was externally validated against the National Reference Laboratory of University Hospitals, Leuven, Belgium, as well as in two international independent external quality control programs (QCMD, Scotland, UK, and Instand, Düsseldorf, Germany, www.instand-ev.de).Second, there is an inherent trade-off between test sensitivity and specificity. In a situation with limited availability of an imperfect reference test, sensitivity is typically preferred over specificity, and a low threshold for diagnosis is used. As previous studies reported a very high sensitivity (97% vs 86% in our study), this negatively affected specificity (2,4).Third, our study should not be read as superior performance of low-dose versus standard-dose CT. However, excellent reproducibility and accuracy suggests low-dose is sufficient for diagnosis and radiation exposure should be reduced. We used CareDose4D (Siemens Healthineers) to adapt radiation parameters, including CarekV which selects the optimal tube voltage. New techniques may ever further reduce radiation exposure (6).Fourth, the prevalence of pneumonia from non–COVID-19 viruses (the most challenging differential diagnosis of COVID-19 on CT) in our cohort was very low, further increasing CT specificity.In conclusion, differences in study populations and reference tests change the estimated performance of a screening test. Careful consideration of these differences is necessary to place research results in a proper clinical context. Disclosures of Conflicts of Interest: A. Dangis disclosed no relevant relationships. C.G. disclosed no relevant relationships. Y.D.B. disclosed no relevant relationships. L.J. disclosed no relevant relationships. H.V. disclosed no relevant relationships. D.O. disclosed no relevant relationships. M.G. disclosed no relevant relationships. M.V.R. disclosed no relevant relationships. J.F. disclosed no relevant relationships. A. Demeyere disclosed no relevant relationships. R.S. disclosed no relevant relationships.References1. Dangis A, Gieraerts C, De Bruecker Y, et al. Accuracy and reproducibility of low-dose submillisievert chest CT for the diagnosis of COVID-19. Radiol Cardiothorac Imaging 2020;2(2):e200196. Link, Google Scholar2. Ai T, Yang Z, Hou H, et al. Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases. Radiology 2020 Feb 26:200642 [Epub ahead of print] Link, Google Scholar3. Kim H, Hong H, Yoon SH. Diagnostic Performance of CT and Reverse Transcriptase-Polymerase Chain Reaction for Coronavirus Disease 2019: A Meta-Analysis. Radiology 2020 Apr 17:201343 [Epub ahead of print] Link, Google Scholar4. Caruso D, Zerunian .M, Polici M, et al. Chest CT Features of COVID-19 in Rome, Italy. Radiology 2020 Apr 3:201237 [Epub ahead of print] Link, Google Scholar5. Bai HX, Hsieh B, Xiong Z, et al. Performance of Radiologists in Differentiating COVID-19 From Viral Pneumonia on Chest CT. Radiology 2020 Mar 10:200823 [Epub ahead of print]. Link, Google Scholar6. Symons R, Pourmorteza A, Sandfort V, et al. Feasibility of Dose-reduced Chest CT with Photon-counting Detectors: Initial Results in Humans. Radiology 2017;285(3):980–989. Link, Google ScholarArticle HistoryPublished online: May 27 2020 FiguresReferencesRelatedDetailsCited ByUltra-Low-Dose Computed Tomography Chest for Screening of COVID-19 PatientsA. V.Prabhakaran, P. 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