【Cochrane简语概要】胸部影像诊断COVID-19的准确性如何?

此问题为何重要？

COVID-19疑似者需要快速知晓其是否有感染，从而使其接受适当的治疗，进行自我隔离，并通知密接者。

目前，COVID-19的正式诊断需要对鼻和咽喉样本进行实验室检查，即逆转录酶聚合酶链反应（reverse transcriptase polymerase chain reaction, RT-PCR）。RT-PCR需要专业的设备，且至少要24小时才出结果。检测结果并非完全准确，还可能需做第二次RT-PCR或用不同的检测来确认诊断。

临床医生可能会用胸部影像来对有COVID-19症状者进行诊断，在其等待RT-PCR结果或RT-PCR结果为阴性时。

这是本综述的第4版。

（图片来自699.pic）

我们想了解什么？

我们想了解胸部影像是否足够准确以用于对COVID-19疑似感染者进行诊断；我们只纳入了针对COVID-19疑似者的研究，排除了对COVID-19确诊者的研究。我们也想评估胸部影像在筛查无症状者中的诊断准确性。

证据更新至2021年2月17日。

什么是胸部影像检查？

X线或扫描产生胸部器官及结构图像。

-X线（放射影像术）采用射线以生成二维（two-dimension, 2-D）图像。通常是由放射科医生使用固定设备在医院内完成，也可在便携式机器上完成。

-电子计算机断层扫描（computed tomography, CT）用电脑合并2-D的X线图像，并将其转换为三维（three-dimension, 3-D）图像。它们需要高度专业化的设备，并需要由放射专科医生在医院完成。

-超声扫描是用高频声波来生成图像。它们可在医院或其他医疗场所（如医生诊所）完成。

我们做了什么？

我们检索了评估胸部影像对任何年龄COVID-19疑似者进行COVID-19诊断的准确性的研究。我们纳入了“症状性”或“混合性人群”的研究。

我们发现了什么?

我们发现了94项研究，有37631名受试者，其中19768名（53%）最终诊断为COVID-19，用以评估胸部影像在评价COVID-19疑似者中的诊断准确性。87项研究评价了一种成像方式，7项研究评价了两种成像方式。所有94项研究均采用单独RT-PCR或联用其他标准（如临床体征和症状或阳性接触）来作为COVID-19诊断的参考标准。

胸部CT：疑似者

合并结果显示，胸部CT（69项研究）在87%的COVID-19患者中正确诊断出了COVID-19。然而，它在21%的COVID-19非患者中错误地检出了COVID-19患者。

胸部X线：疑似者

合并结果显示，胸部X线（17项研究）在73%的COVID-19患者中正确诊断出了COVID-19。然而，它在27%的COVID-19非患者中错误地检出了COVID-19。

肺部超声：疑似者

合并结果显示，肺部超声（15项研究）在87%的COVID-19患者中正确诊断出了COVID-19。然而，它在24%的COVID-19非患者中错误诊断出了COVID-19。

筛查无症状者

我们纳入了10项研究（7项CT、1项X线、2项超声），有3548名无症状受试者，其中364名（10%）最终诊断为COVID-19。7项研究的合并结果显示，CT正确诊断了56%的COVID-19患者，错误诊断了8%的COVID-19非患者。

研究结果如何可靠？

这些研究各不相同，且采用不同的方法报告其结果。没有几项研究直接比较一种影像学检查与另一种。此外，在所有纳入研究中，约有一半的偏倚风险为高或不明确。因此，很难得出有把握的结论。

这意味着什么？

有证据表明，胸部CT和超声可更好排除COVID-19感染，相较于把其与其他呼吸系统疾病区分开。因此，其有用性可能限于排除COVID-19感染，而非将其与其他原因所致肺部感染区分开来。此外，胸部CT对无症状个体的检测敏感度为差，特异度为高。

作者结论: 

胸部CT和肺部超声对COVID-19诊断敏感，并有中等特异度。胸部X线对COVID-19诊断具有中等敏感度和中等特异度。因此，胸部CT和超声在排除COVID-19方面可能比在区分SARS-CoV-2感染与其他呼吸道疾病方面更有用。纳入研究的高或不明确偏倚风险及异质性导致的不确定性，限制了我们根据结果自信做出结论的能力。

作者:Ebrahimzadeh S, Islam N, Dawit H, Salameh J-P, Kazi S, Fabiano N, Treanor L, Absi M, Ahmad F, Rooprai P, Al Khalil A, Harper K, Kamra N, Leeflang MMG, Hooft L, van der Pol CB, Prager R, Hare SS, Dennie C, Spijker R, Deeks JJ, Dinnes J, Jenniskens K, Korevaar DA, Cohen JF, Van den Bruel A, Takwoingi Y, van de Wijgert J, Wang J, Pena E, Sabongui S, McInnes MDF；译者：陶安，Cochrane Hong Kong，香港中文大学医学院那打素护理学院；审校：臧渝梨，Cochrane Hong Kong，香港中文大学医学院那打素护理学院；编辑排版：索于思，北京中医药大学循证医学中心

相关文章链接

【Cochrane Plain Language Summary】

How accurate is chest imaging for diagnosing COVID-19?

Why is this question important?

People with suspected COVID-19 need to know quickly whether they are infected, so they can receive appropriate treatment, self-isolate, and inform close contacts.

Currently, a formal diagnosis of COVID-19 requires a laboratory test (RT-PCR) of nose and throat samples. RT-PCR requires specialist equipment and takes at least 24 hours to produce a result. It is not completely accurate, and may require a second RT-PCR or a different test to confirm diagnosis.

Clinicians may use chest imaging to diagnose people who have COVID-19 symptoms, while awaiting RT-PCR results or when RT-PCR results are negative, and the person has COVID-19 symptoms.

This is the fourth version of this review.

What did we want to find out?

We wanted to know whether chest imaging is accurate enough to diagnose COVID-19 in people with suspected infection; we included studies in people with suspected COVID-19 only and excluded studies in people with confirmed COVID-19. We also wanted to assess the accuracy of chest imaging for screening asymptomatic people.

The evidence is up to date to 17 February 2021.

What are chest imaging tests?

X-rays or scans produce an image of the organs and structures in the chest.

- X-rays (radiography) use radiation to produce a 2-D image. Usually done in hospitals, using fixed equipment by a radiographer; they can also be done on portable machines.

- Computed tomography (CT) scans use a computer to merge 2-D X-ray images and convert them to a 3-D image. They require highly-specialized equipment and are done in hospital by a specialist radiographer.

- Ultrasound scans use high-frequency sound waves to produce an image. They can be done in hospitals or other healthcare settings, such as a doctor’s office.

What did we do?

We searched for studies that assessed the accuracy of chest imaging to diagnose COVID-19 in people of any age with suspected COVID-19. We included studies with ‘symptomatic' or 'mixed populations'.

What did we find?

We found 94 studies with 37,631 participants (of whom 19,768 (53%) had a final diagnosis of COVID-19) for evaluating the diagnostic accuracy of thoracic imaging in the evaluation of people with suspected COVID-19. Eighty-seven studies evaluated one imaging modality, and seven studies evaluated two imaging modalities. All 94 studies used RT-PCR either alone or in combination with other criteria (such as clinical signs and symptoms, or positive contacts) as the reference standard for the diagnosis of COVID-19.

Chest CT: suspected people

Pooled results showed that chest CT (69 studies) correctly diagnosed COVID-19 in 87% of people who had COVID-19. However, it incorrectly identified COVID-19 in 21% of people who did not have COVID-19.

Chest X-ray: suspected people

Pooled results showed that chest X-ray (17 studies) correctly diagnosed COVID-19 in 73 % of people who had COVID-19. However, it incorrectly identified COVID-19 in 27% of people who did not have COVID-19.

Lung ultrasound: suspected people

Pooled results showed that lung ultrasound (15 studies) correctly diagnosed COVID-19 in 87% of people with COVID-19. However, it incorrectly diagnosed COVID-19 in 24% of people who did not have COVID-19.

Screening asymptomatic people

We included 10 studies (7 CT, 1 X-ray, 2 ultrasound) with 3548 asymptomatic participants, of whom 364 (10%) had a final diagnosis of COVID-19. Pooled results of seven studies, showed that CT correctly diagnosed COVID-19 in 56% of people who had COVID-19, and incorrectly identified COVID-19 in 8% of people who did not have COVID-19.

How reliable are the results?

The studies differed from each other and used different methods to report their results. Very few studies directly compared one type of imaging test with another. Also, the risk of bias was high or unclear in about half of all included studies. Therefore, it is difficult to draw confident conclusions.

What does this mean?

The evidence suggests that chest CT and ultrasound are better at ruling out COVID-19 infection than distinguishing it from other respiratory problems. So, their usefulness may be limited to excluding COVID-19 infection rather than differentiating it from other causes of lung infection. In addition, chest CT imaging had poor sensitivity and high specificity for detecting asymptomatic individuals.

Authors' conclusions: 

Chest CT and ultrasound of the lungs are sensitive and moderately specific in diagnosing COVID-19. Chest X-ray is moderately sensitive and moderately specific in diagnosing COVID-19. Thus, chest CT and ultrasound may have more utility for ruling out COVID-19 than for differentiating SARS-CoV-2 infection from other causes of respiratory illness. The uncertainty resulting from high or unclear risk of bias and the heterogeneity of included studies limit our ability to confidently draw conclusions based on our results.

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