【病毒外文文獻】2004 High-Resolution Computed Tomography Is Useful for Early Diagnosis of Severe Acute Respiratory Syndrome_Associated C

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ORIGINAL ARTICLE High Resolution Computed Tomography Is Useful for Early Diagnosis of Severe Acute Respiratory Syndrome Associated Coronavirus Pneumonia in Patients with Normal Chest Radiographs Joyce Yee Hing Hui FRCR Timothy Yu Wai Hon FRCR Michael Kwok Wai Yang MBBS Danny Hing Yan Cho MBBS Wing Hang Luk FRCR Ronee Yun Yee Chan FRCR Kin Sang Chan FRCP Tony Kwok Loon Loke FRCR and James Chi Sang Chan FRCR Objective We investigated the usefulness of high resolution com puted tomography HRCT in early detection of severe acute respira tory syndrome SARS associated coronavirus pneumonia and ana lyzed HRCT findings associated with potentially more severe dis ease Methods All patients with suspected SARS and normal chest ra diographs on admission within the study period were subjected to HRCT examination The clinical radiologic and laboratory data of patients who were confirmed to have SARS associated coronavirus infection by a positive nasopharyngeal aspirate stool or urine reverse transcription polymerase chain reaction RT PCR and or serological testing were prospectively followed up and analyzed Characteristics of patients admitted to the intensive care unit ICU and those that were not were compared Results Among 47 suspected SARS patients with normal chest ra diographs 27 had SARS associated coronavirus infection confirmed by RT PCR and or positive serological testing Twenty five of the 27 93 patients had HRCT changes compatible with atypical pneumo nia and all 25 patients developed SARS with progressive clinical deterioration Ten 40 had unifocal diseases and 15 had multifocal diseases 60 Ten 40 patients had the diseases confined to 1 single lung in the first HRCT and both lungs were involved at initial presentation in 15 60 patients Concerning the overall extent of the disease at initial presentation 3 12 patients had disease process in all lobes and the disease was confined to 1 single lobe in 10 40 patients The disease process was mainly peripheral in location 96 and the lower lobes were more commonly involved 68 in the left lower lobe and 64 in the right lower lobe Small parapneu monic effusions occurred in 1 4 patient None of the patients with unifocal lesions or single lung involvement were admitted to the ICU P 0 05 in both comparisons Subsequent follow up of the 2 7 patients with normal HRCT on admission showed that they were hav ing nonpneumonic SARS associated coronavirus infection only and were eventually denotified from having SARS Conclusions HRCT is useful for early diagnosis of SARS associated coronavirus pneumonia in patients with normal chest ra diographs HRCT findings in these patients predict potentially severe disease Key Words atypical pneumonia coronavirus high resolution com puted tomography severe acute respiratory syndrome J Comput Assist Tomogr 2004 28 1 9 A n outbreak of atypical pneumonia leading to the severe acute respiratory syndrome SARS has recently occurred in our community Evidence is accumulating that the disease is caused by a novel coronavirus 1 5 The disease has high mor tality and the most efficacious treatment is still not estab lished A substantial number of health care workers have been infected despite all sorts of preventive measures and the dis ease is causing major concerns throughout the world The pub lic is recommended to seek medical advice if they develop a sudden high fever and 1 or more respiratory symptoms espe cially those with known contact or history of travel to affected areas We are now facing a huge group of patients who are highly alert to the condition and present early with nonspecific symptoms and signs that may suggest SARS Chest radio graphs are well known to be insensitive in the detection of subtle abnormalities in the lungs with blind areas on frontal view making up to 40 of the lung area and 25 of the lung volume 6 7 All rapid diagnostic tests for SARS are still in their developmental phase and cannot be used to exclude SARS and are not useful for screening Their sensitivities and specifici ties are yet to be established 5 From the Department of Diagnostic Radiology and Organ Imaging Drs Hui Hon Yang Cho Luk R Y Y Chan Loke and J C S Chan and the Respiratory Division Department of Medicine Dr K S Chan United Christian Hospital Kwun Tong Hong Kong Reprints Dr J Y H Hui Department of Diagnostic Radiology and Organ Imaging United Christian Hospital 130 Hip Wo Street Kwun Tong Hong Kong e mail jhuiyh hk Copyright 2004 by Lippincott Williams GE Medical Systems Milwaukee WI One millimeter thick transverse sections were obtained from the lung apices through the bases at 10 mm increments with the patients in the supine position during full inspiration Images were reconstructed using a high spatial frequency al gorithm The CT images were reviewed in cine formats at a computer workstation CT Advantage Windows 3 1 Advan tage GE Medical Systems Milwaukee WI by 2 thoracic ra diologists J Y H H and T Y W H Images were examined at both standard lung and soft tissue settings Increased lung opacification was defined as ground glass when there was a hazy increase in attenuation without obscuration of the pulmonary vasculature and as consolidation when there was obscuration of the pulmonary vessels For le sions containing both ground glass and consolidative compo nents the predominant changes are counted as the pattern of reference The pattern distribution and extent of pulmonary parenchymal abnormalities were recorded according to con sensus opinion The disease extent was evaluated both in terms of the number of lungs involved lobes involved the lingula was considered as a separate lobe and the number of lesion s in each lobe A lesion was regarded to be central in location if it occurred within the inner half of the lung field and peripheral in location if it involved only the peripheral one half of the lung The presence of any dilated airways within the abnormal lung was observed Size of the largest diameter of ground glass opacity and or consolidation missed on the chest radio graphs and their possible explanations were recorded The presence of any thickened interlobular septum thickening of intralobular interstitium lymphadenopathy pleural effusion and cavitating lung lesion was also noted A comparison of characteristics was made between pa tients who were admitted to the intensive care unit ICU re quiring oxygen therapy and ventilatory support and those who were not The 2 patients with normal HRCT were excluded from statistical analysis Analyses were performed using SPSS version 11 SPSS Chicago IL H9273 2 test was used for categori cal variables and Student t test for continuous variables P 0 05 was regarded as statistically significant Multivariate analysis was not performed because of small sample size RESULTS A total of 155 patients were admitted to the United Christian Hospital with suspected SARS from 26 March 2003 to 7 April 2003 HRCT of the thorax was performed in 47 30 patients with normal chest radiographs on admission Among these 47 patients 27 had diagnosis of SARS associated coronavirus infection confirmed by RT PCR and or positive serological testing and were included in the analysis The clinical characteristics and laboratory findings of the 27 patients were tabulated and are summarized in Tables 1 and 2 The male to female ratio was 10 17 The median age was 41 years range 20 77 years All were nonsmokers The ma jority of our patients enjoyed good past health Concerning the history of exposure 19 70 patients were residents in an outbreak housing estate Amoy Gardens and 4 15 were health care workers taking care of affected cases in our hospi tal Table 2 Four 15 patients had no known history of contact All patients except 1 96 had fever None of the 27 patients had shortness of breath or any positive physical sign on admission The HRCT findings of our patients were tabulated and are summarized in Tables 1 and 3 HRCT was performed at a median duration of 2 days range 0 6 days from the onset of Hui et al J Comput Assist Tomogr Volume 28 Number 1 January February 2004 2 2004 Lippincott Williams SARS severe acute respiratory syndrome HT hypertension DM diabetes mellitus H9252 Thal trait H9252 Thalas semia trait UG unifocal ground glass opacity UC unifocal consolidation MG multifocal ground glass opacities MGC multifocal ground glass opacity ies and consolidation s N normal L left R right L R left and right NA not available GGO ground glass opacity J Comput Assist Tomogr Volume 28 Number 1 January February 2004 HRCT in Detection of SARS Associated Coronavirus 2004 Lippincott Williams SARS severe acute respi ratory syndrome J Comput Assist Tomogr Volume 28 Number 1 January February 2004 HRCT in Detection of SARS Associated Coronavirus 2004 Lippincott Williams with their sensitivities and specificities unestablished they cannot be used to exclude SARS Although chest radiograph remains the most commonly used modality in the investigation and follow up of patients with SARS coronavirus pneumonia there are well known regions in the frontal chest radiographs that are difficult to be assessed because of overlapping normal structures 6 These known limitations and pitfalls of chest ra diographs necessitate the use of HRCT which has improved the detectability of many subtle and small lesions since its ad vent and has become an indispensable tool in the evaluation of suspected diffuse pulmonary disease during the past 15 years 14 In the current study 15 60 patients had their le FIGURE 3 A 33 year old woman with SARS associated coro navirus pneumonia High resolution computed tomography on day 4 from the onset of symptom shows a centrally locating consolidation in the left upper lobe surrounded by a halo of ground glass changes arrow FIGURE 5 A 47 year old woman with SARS associated coro navirus pneumonia High resolution computed tomography on day 1 from the onset of symptom shows multifocal ground glass opacities in the right middle and lower lobes arrows A consolidation arrowhead with air bronchogram is found in the left lower lobe Small parapneumonic effusions double arrows are also seen FIGURE 2 A 23 year old woman with SARS associated coro navirus pneumonia High resolution computed tomography on day 5 from the onset of symptom demonstrates a dense consolidation with air bronchogram in the left lung base ob scured by cardiac shadow FIGURE 4 A 36 year old man with SARS associated coronavi rus pneumonia High resolution computed tomography on day 3 from the onset of symptom shows multifocal ground glass opacifications in the left and right lower lobes arrows Hui et al J Comput Assist Tomogr Volume 28 Number 1 January February 2004 6 2004 Lippincott Williams HRCT high resolution computed tomography J Comput Assist Tomogr Volume 28 Number 1 January February 2004 HRCT in Detection of SARS Associated Coronavirus 2004 Lippincott Williams these despite the fact that individuals who had normal chest radiographs were expected to have fewer le sions detected on HRCT This is because of the supreme ability of HRCT in the detection of small and subtle pulmonary ab normalities Similar to other reported series 13 the lower lobes were more commonly involved 68 in the left lower lobe and 64 in the right lower lobe and the disease process was usually peripheral in location 96 It was observed that consolidation up to 63 8 mm and ground glass changes up to 96 2 mm in diameter could be missed by chest radio graphs This figure appeared to have slightly exaggerated the actual situation because consolidation and ground glass changes are in fact a continuum In our study consolidation may have been encircled by a halo of ground glass changes but yet they were still classified as consolidation Fig 3 Small parapneumonic effusions occurred in 1 4 patient None of our patients had cavitation or hilar lymphadenopathy at presentation In addition to helping in early diagnosis of SARS associated coronavirus pneumonia HRCT findings also pre dicted patients with subsequently more severe disease In our study a greater degree of pulmonary damage on initial HRCT as evident by the detection of abnormality in more than 1 lobe and bilateral lung involvement correlates well with severe complicated disease with oxygen desaturation requiring ven tilatory support in the ICU None of the patients with unifocal lesions or single lung involvement were admitted to the ICU P 0 05 in both comparisons Previous studies of pulmo nary reovirus infection in athymic mice had shown that a lower plaque forming value of 10 6 is associated with pathologic changes of bronchiolitis obliterans organizing pneumonia whereas a larger inoculum of 10 7 is associated with develop ment of histologic characteristics of acute respiratory distress syndrome 16 Moreover similar to other studies 3 those patients with more severe SARS were also found to have a higher se rum lactate dehydrogenase and creatinine kinase level on ad mission This means that the initial viral innocula in patients with SARS may be one of the factors affecting the subsequent disease severity Early identification of these patients allows prompt treatment and close monitoring to be given to those who are at risk There are certain limitations to our study First this pre liminary study was limited by the relatively small number of patients included Second there was also a lack of an age and sex matched control group of patients who had suspected SARS but were subsequently confirmed not to have SARS associated coronavirus infection However according to our preliminary experience we have not seen a single patient with normal HRCT who developed SARS Further studies are nec essary to delineate the negative predictive value of HRCT in patients with suspected SARS CONCLUSIONS Although the best logistics for diagnosis of SARS associated coronavirus pneumonia depend on the availability of various microbiological tests and radiologic modalities in different centers the current study had shown that HRCT is useful in early detection and diagnosis of SARS associated coronavirus pneumonia before radiographic abnormalities were present In the correct clinical and epidemiological set tings the presence of multifocal ground glass opacity ies with or without consolidation s in the peripheral area of the lower lobes are highly suggestive of SARS associated corona virus pneumonia REFERENCES 1 Poutanen SM Low DE Henry B et al Identification of severe acute re spiratory syndrome in Canada N Engl J Med 2003 348 1995 2005 2 Tsang KW Ho PL Ooi GC et al A cluster of cases of severe acute respiratory syndrome in Hong Kong N Engl J Med 2003 348 1977 1985 3 Lee N Hui D Wu A et al A major outbreak of severe acute respiratory syndrome in Hong Kong N Engl J Med 2003 348 1986 1994 4 Peiris JSM Lai ST Poon LLM et al Coronavirus as a possible cause of severe acute respiratory syndrome Lancet 2003 361 1319 1325 5 Ksiazek TG Erdman D Goldsmith C et al A novel coronavirus 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