Meta分析：电脑断层结肠镜

布莱恩·P.马尔霍尔，MD，MPH;加尼甚·Veerappan，MD;和杰弗里·杰克逊，MD，MPH
Brian P. Mulhall, MD, MPH; Ganesh R. Veerappan, MD; and Jeffrey L. Jackson, MD, MPH

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背景： 计算机体层摄影（CT）结肠镜检查，也被称为虚拟结肠镜检查，是一个不断发展的技术，正在评估作为一个新的大肠癌筛查方法。但是作为一个测试，其性能变化广泛的研究，以及这些差异的原因是不好界定。

目的： 系统地审查测试中的表现相比，结肠镜检查或手术的CT结肠成像和评估，可能会影响测试性能的变量。

数据来源： 1975年1月和2005年2月出版的英语文章的PubMed，MEDLINE和EMBASE数据库和Cochrane对照试验注册搜索。

研究选择： 成人的前瞻性研究，充分的肠道准备后，进行CT结肠成像与结肠镜检查或手术的金标准，进行选择。研究必须使用国家的最先进的技术，其中包括至少一个探测器CT扫描仪，仰卧和俯卧位，充气的结肠与空气或二氧化碳，准直小于5毫米，和两个2维和3维扫描过程中解释的意见。评估的colonogram的黄金标准测试的结果是不知道的。

数据抽象： 的灵敏度和特异性的整体上的数据和用于检测息肉小于6毫米，6至9毫米，和大于9毫米大小抽象。的敏感性和特异性样本量加权计算，并通过使用分层分析和meta回归异质性进行了探讨。

数据综合： 33项研究提供的数据，对6393例患者。CT结肠成像的灵敏度是多种多样的，但是改善息肉的大小增加（48％[95％CI，25％&#12316;70％]检测息肉<6毫米，70％[CI，55％&#12316;84％的息肉6 9毫米，85％CI，79％至91％]为息肉> 9毫米）。CT结肠成像扫描仪的特性，包括准直，探测器类型和模式的成像宽度，解释了这种异质性。相反，特异性为均匀（92％[CI，89％&#12316;96％]检测息肉<6毫米，93％[CI，91％&#12316;95％[6至9毫米，97％的息肉[CI， 96％至97％]为息肉> 9毫米）。

限制： 研究大不相同，和可萃取的变量解释只有少量的非均质性。此外，只有少数的研究探讨最新的CT结肠成像技术。

结论： 电脑断层结肠镜检查是非常具体的，但很宽的范围内报告的敏感性。患者或扫描仪的特点没有充分考虑这种差异，但准直，类型的扫描仪和成像方式解释一些差异。这种异质性提高的性能一致性和有关技术变化的担忧。这些问题必须得到解决之前，CT结肠成像可以主张广义大肠癌筛查。

大肠癌在美国癌症相关死亡的第二个最常见的原因。近150万新发病例，60万人死亡，每年发生这种疾病（1）。由于大肠癌的发展不知不觉地随着时间的推移无临床症状的腺瘤性息肉基因突变的积累，它是最常见的诊断为晚期（2  -  4）。如果条件的早期诊断，预后良好，5年生存率超过90％（5  -  6）。不像许多其他类型的癌症中，大肠癌，可以防止去除癌前病变。已建立的长的临床前阶段，早期探测性，和改进的结肠直肠癌预后的一个准确的检查方法的需要。

目前使用的各种检查测试，降低发病率和死亡率，大肠癌（7  -  8）。然而，尽管这些试验证明疗效，病人的依从性筛选准则是低，只有30％至45％的人有资格进行筛选，进行这样的测试。坚持低利率被认为是由于不良的公众意识和市民的接受程度，目前的筛查技术（9  -  13）差。

大肠癌的筛选试验是一种日益流行的电脑断层（CT）结肠镜检查，也被称为如CT colography的或虚拟结肠镜检查。第一次是在1994年，薄截面图像的充气X射线照相技术可以重建复杂的电脑断层结肠镜检查成高分辨率的2 -和3 -维的图像（14）的软件。随着时间的推移，在硬件和软件方面的改进允许更快的扫描，减少暴露在辐射中，较好的成像质量。较新的成像模式（称为飞通），可以产生类似的结果，内窥镜图像，并允许复杂的表征的检测病变（15  -  17）。早期的研究主要使用螺旋CT扫描仪，它在小息肉更难以检测（17）的空间分辨率，因此可以使具有局限性。多排螺旋CT扫描仪可快速采集获得更精细的图像，在一个单一的屏气，可以大大提高图像质量和空间分辨率（17  -  18）。这项技术正在研究的许多方面，包括软件，可以帮助发现病灶，改进的图像重建，粪便标记（19  -  21）。后者的开发依赖于摄入对比材料超过数天或小时，之后，软件数字减去残余固体和流体的粪便材料从所获取的图像，创建“几乎干净”粘膜表面（22  -  23）。此技术可提高灵敏度，并可能有一天不再需要在考试前的清肠。

虽然它被吹捧为一种微创的检查方法比软式乙状结肠镜或结肠镜检查，CT结肠成像通常需要通过直肠（24）充分的肠道清洗和充入空气。有研究表明，CT结肠镜检查可能是相似的，在某些情况下，最好，结肠镜检查的舒适性和可接受性方面，但没有令人信服的区别这两种方法已被证明（25  -  31）。，如果虚拟结肠镜检查发现具有同等的测试特性，提高病人的依从性，安全或成本低于结肠镜检查，可能会更符合成本效益，并成为选择的筛选方法（32  -  33）。

CT结肠成像的测试特性的研究有不同的结果。90-104和他的同事们使用CT结肠镜检查1233例，发现腺瘤性息肉大于8毫米（25）的敏感性为93.9％ 。其他的研究也有较有利的结果，低至55％，大于10毫米的息肉的敏感性，提高整体测试性能的CT结肠成像的担忧，在更广阔的范围内设置（34）。这些差异的结果已提供的各种原因，但这种异质性的来源还没有被充分挖掘（16，35  -  36）。这样的评估是必要的，因为患者和供应商希望这项技术，希望提高筛检率（29）。

我们系统地回顾了文学的评估测试中的表现相比，CT结肠与结肠镜检查或手术，以确定这些研究的特点，并试图解释的来源，冲突的结果。

Background: Computed tomographic (CT) colonography, also called virtual colonoscopy, is an evolving technology under evaluation as a new method of screening for colorectal cancer. However, its performance as a test has varied widely across studies, and the reasons for these discrepancies are poorly defined.

Purpose: To systematically review the test performance of CT colonography compared to colonoscopy or surgery and to assess variables that may affect test performance.

Data Sources: The PubMed, MEDLINE, and EMBASE databases and the Cochrane Controlled Trials Register were searched for English-language articles published between January 1975 and February 2005.

Study Selection: Prospective studies of adults undergoing CT colonography after full bowel preparation, with colonoscopy or surgery as the gold standard, were selected. Studies had to have used state-of-the-art technology, including at least a single-detector CT scanner with supine and prone positioning, insufflation of the colon with air or carbon dioxide, collimation smaller than 5 mm, and both 2-dimensional and 3-dimensional views during scan interpretation. The evaluators of the colonogram had to be unaware of the findings from use of the gold standard test.

Data Abstraction: Data on sensitivity and specificity overall and for detection of polyps less than 6 mm, 6 to 9 mm, and greater than 9 mm in size were abstracted. Sensitivities and specificities weighted by sample size were calculated, and heterogeneity was explored by using stratified analyses and meta-regression.

Data Synthesis: 33 studies provided data on 6393 patients. The sensitivity of CT colonography was heterogeneous but improved as polyp size increased (48% [95% CI, 25% to 70%] for detection of polyps <6 mm, 70% [CI, 55% to 84%] for polyps 6 to 9 mm, and 85% [CI, 79% to 91%] for polyps >9 mm). Characteristics of the CT colonography scanner, including width of collimation, type of detector, and mode of imaging, explained some of this heterogeneity. In contrast, specificity was homogenous (92% [CI, 89% to 96%] for detection of polyps <6 mm, 93% [CI, 91% to 95%] for polyps 6 to 9 mm, and 97% [CI, 96% to 97%] for polyps >9 mm).

Limitations: The studies differed widely, and the extractable variables explained only a small amount of the heterogeneity. In addition, only a few studies examined the newest CT colonography technology.

Conclusions: Computed tomographic colonography is highly specific, but the range of reported sensitivities is wide. Patient or scanner characteristics do not fully account for this variability, but collimation, type of scanner, and mode of imaging explain some of the discrepancy. This heterogeneity raises concerns about consistency of performance and about technical variability. These issues must be resolved before CT colonography can be advocated for generalized screening for colorectal cancer.

Colorectal cancer is the second most frequent cause of cancer-related death in the United States. Nearly 150&#8201;000 new cases and 60&#8201;000 deaths occur each year from this disease (1). Because colorectal cancer develops insidiously over time as genetic mutations accumulate in clinically silent adenomatous polyps, it is most commonly diagnosed at an advanced stage (2 - 4). If the condition is diagnosed at an early stage, the prognosis is favorable, with 5-year survival rates exceeding 90% (5 - 6). Colorectal cancer, unlike many other types of cancer, can be prevented by removal of precancerous lesions. The long preclinical phase, early detectability, and improved prognosis of colorectal cancer have established the need for an accurate screening method.

Various screening tests in current use reduce the incidence and rate of death from colorectal cancer (7 - 8). Despite the proven efficacy of these tests, however, patient adherence to screening guidelines is low: Only 30% to 45% of persons eligible for screening undergo such tests. Low adherence rates are believed to be due to poor public awareness and poor public acceptance of current screening techniques (9 - 13).

An increasingly popular screening test for colorectal cancer is computed tomographic (CT) colonography, also known as CT colography or virtual colonoscopy. Computed tomographic colonography was first described in 1994 as a radiographic technique in which thin-section images of pneumocolon could be reconstructed by sophisticated software into high-resolution 2- and 3-dimensional images (14). Over time, improvements in hardware and software have allowed faster scanning, reduced exposure to radiation, and better imaging. Newer modes of imaging (called fly-through) can produce results that resemble endoscopic images and permit sophisticated characterization of detected lesions (15 - 17). Early studies primarily used the spiral CT scanner, which has limitations in spatial resolution that can make small polyps more difficult to detect (17). The multidetector CT scanner has permitted rapid acquisition of finer images, obtained during a single breath-hold, that can greatly improve image quality and spatial resolution (17 - 18). Many aspects of this technology are under study, including software that assists in detection of lesions, refinements in image reconstruction, and stool tagging (19 - 21). The latter development relies on ingestion of contrast material over several days or hours, after which software digitally subtracts residual solid and fluid fecal material from the acquired images, creating a “virtually clean” mucosal surface (22 - 23). This technique may improve sensitivity and may someday obviate the need for bowel cleansing before examination.

Although it is touted as a less invasive screening method than flexible sigmoidoscopy or colonoscopy, CT colonography typically requires full bowel cleansing and insufflation of air through the rectum (24). Studies have suggested that CT colonography may be similar, and in some cases preferable, to colonoscopy in terms of comfort and acceptability, but no convincing difference between these 2 approaches has been demonstrated (25 - 31). If virtual colonoscopy is found to have equivalent test characteristics, improve patient adherence, and be safer or less expensive than colonoscopy, it may be more cost-effective and become the screening method of choice (32 - 33).

Studies of the test characteristics of CT colonography have had mixed results. Pickhardt and colleagues used CT colonography in 1233 patients and found a sensitivity of 93.9% for adenomatous polyps larger than 8 mm (25). Other studies have had less favorable results, with sensitivities as low as 55% for polyps larger than 10 mm, raising concerns about the overall test performance of CT colonography when used in a broader range of settings (34). Various reasons for these discrepant results have been offered, but the source of this heterogeneity has not been fully explored (16,35 - 36). Such assessment is needed because patients and providers look to this technology in the hope of improving screening rates (29).

We systematically reviewed the literature to assess the test performance of CT colonography compared with colonoscopy or surgery, to define characteristics of these studies, and to attempt to explain the sources of conflicting results.

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