Key Points

• Fecal immunochemical test (FIT) stool samples with the lightest color had significantly lower fecal hemoglobin (Hb) levels than all darker classes.
• It is reassuring that among the 467 patients who underwent colonoscopy regardless of FIT results, light‐color samples did not yield higher false‐negative results for colorectal cancer and advanced adenomas.

“It's important that … patients are provided with simple instructions that highlight the importance of adequate fecal sample collection.”—Erin Symonds, PhD

Recent surveys suggest that many people, concerned about contracting coronavirus disease 2019 (COVID‐19) through public exposure, have been forgoing cancer screening tests. (The American Society of Clinical Oncology, for example, found that approximately two‐thirds of those who were scheduled to receive cancer screenings during the pandemic reported missing or delaying them.) Although fecal occult blood tests, including FIT, that can be performed at home offer a good solution for most individuals who are concerned about getting a screening colonoscopy at this time, some previous studies have raised concerns that suboptimal stool collection by patients might lead to false‐negative results.

Most studies of pre‐analytic variables to date have focused on those occurring after collection, such as storage and ambient temperatures and time lags before analysis, resulting in degradation of the fecal Hb, which can lead to false‐negative results. However, a new study by Australian investigators investigates whether there needs to be greater emphasis on stricter adherence to the collection of the stool samples themselves, particularly the amount collected, to ensure the diagnostic accuracy of the tests. The research appears in Cancer Epidemiology, Biomarkers & Prevention (doi:10.1158/1055-9965.EPI-20-0984).

“This type of study has never been done before,” says the lead author, Erin Symonds, PhD, a senior research scientist and team leader at Flinders Medical Centre and an associate professor at the College of Medicine and Public Health at Flinders University in Bedford Park, South Australia. “We were aware of several studies that had investigated the effect of the post‐collection variables on FIT performance, but no previous studies had assessed the variation in collection technique observed in a clinical setting.”

Dr. Symonds says that her team believed it was imperative to determine whether inconsistencies in sampling quantity affect clinical results for finding advanced neoplasia and other bowel disease because “the use of FIT in the detection of colorectal cancer, whether it is in programmatic or opportunistic screening, surveillance, or symptomatic patients, relies on accurate measurement of Hb to determine which individuals need follow up, usually colonoscopy.”

Study Details

Researchers examined FIT devices (OC‐Sensor; Eiken Chemical Co, Tokyo, Japan) returned by mail to their laboratory by patients at elevated risk for colorectal cancer as determined by Australia's Southern Cooperative Program for the Prevention of Colorectal Cancer, which was developed in 2000 after the release of Australia's National Health and Medical Research Council Guidelines for colorectal cancer prevention. Participants received FIT kits that included detailed instructions, 2 collection devices, 2 sample collection sheets, and a pouch and envelope with a return address. Sample collections took place between January 2019 and February 2020.

Patients were instructed to collect samples at home from the outer surface of the feces of 2 different bowel motions. The collection devices consisted of circumferentially grooved probes for sampling feces. When the collection is performed correctly, the probe is inserted into the device with ideally approximately 10 mg of feces reaching the 2.0 mL of Hb‐stabilizing buffer.

Each subject returned both devices. The researchers noted the number of days between the first and second sample collections and whether the sample had been collected before or after midday.

Once received at the laboratory, the samples were graded for color from 1 to 5 (from lightest to darkest) by 2 investigators for the first 4 months of the study to develop consistent scoring between them. In addition, approximately 650 collection devices were weighed before they were sent to patients and then were re‐weighed upon return to the laboratory after collection to calculate the weight of stool collected. Finally, all samples were assayed to determine fecal Hb levels.

Study Results

Approximately 6898 samples were collected from 3449 individuals. More than half were female (53.1%), and the median age of all subjects was 65.3 years. Of the samples, 362 (5.2%) were graded as the lightest in color, 1836 (26.6%) were judged to be color 2, 2569 (37.2%) were judged to be color 3, 1711 (24.8%) were judged to be color 4, and 420 (6.1%) were the darkest in color (color 5).

Of the 3449 sample pairs, 858 (24.9%) had a darker color on the second sample collection, and 872 (25.3%) of the second samples were lighter; the remaining pairs were judged to be the same color. For the 650 collection devices returned that had their mass recorded before and after sample collection, the median mass of feces collected was 33.8 mg.

The researchers found that color was significantly related to sample mass: colors 2, 3, 4, and 5 had a significantly greater mass than those graded as color 1 (P = .002). They found that the samples with the lightest color had a significantly lower fecal Hb level in comparison with all darker classes (P < .001). Low sample mass was not associated with patient age, sex, or other demographic variables.

On the basis of a subset of study participants (467 patients) who underwent colonoscopy regardless of FIT results, they also determined that undersampling of stool (the lightest colored samples) was not associated with false‐negative results for advanced neoplasia (colorectal cancer and advanced adenomas, with the latter category comprising adenomas with a size and histology indicating a greater risk of evolution to colorectal cancer) but was for colorectal neoplasia overall and inflammatory bowel disease. The false‐negative percentages for the detection of advanced neoplasia were 23.3% and 22.8% for specimens with the lightest color and those in all other color categories, respectively (P = .947).

According to Dr. Symonds, the most important findings from the study were their observation that “… those devices with a light color had the lowest measured fecal Hb concentration and lowest FIT positivity rate, and in addition, that the light‐colored devices conferred an increased risk for a false‐negative result in the detection of any colorectal neoplasia and inflammatory bowel disease together.” However, the study results provide reassurance that suboptimal stool collection is unlikely to reduce sensitivity for identifying patients with the most clinically relevant lesions—colorectal cancers and adenomas—so that they can be referred for diagnostic colonoscopy.

Pandemic Screening Update From the American Cancer Society

In addition to fears that some patients may have about entering a hospital setting during the pandemic, Durado Brooks, MD, MPH, former vice president of cancer control interventions at the American Cancer Society in Atlanta, notes that virtually all health organizations discouraged in‐house, clinical visits last winter and spring, and this caused the number of colorectal screenings to drop significantly.

This, Dr. Brooks says, is where tests such as FIT that patients can perform at home can fill a need—if they are performed correctly. To this end, the National Colorectal Cancer Roundtable has created a resource entitled “Reigniting Colorectal Cancer Screening as Communities Face and Respond to the COVID‐19 Pandemic: A Playbook” (nccrt.org/resource/a-playbook-for-reigniting-colorectal-cancer-screening-as-communities-respond-to-the-covid-19-pandemic). According to the coalition, this document includes the most recent “data, research, and clinical guidelines available related to colorectal cancer screening and COVID‐19” and provides an action‐oriented guide for how members, partners, and colorectal cancer screening advocates can “work together to reignite our screening efforts appropriately, safely, and equally for all communities.”

Regarding self‐screening kits, the playbook states that for people at average risk, tests such as FIT or a stool DNA test (eg, Cologuard) can be performed safely at home. The American Cancer Society does not see these tests as a substitute for diagnostic colonoscopies, however. “If the stool test result is positive, you will need a colonoscopy, and it will be important to talk with your doctor about the safest way to proceed with this. Colonoscopy as a screening test is still an option, but it may be harder to get an appointment now compared to before the COVID‐19 pandemic,” says Dr. Brooks.

For those who can opt for screening at home, Dr. Symonds stresses the importance of the study's findings regarding the quantity and color of the samples. “With more and more people and clinicians encouraging FIT tests, labs should recognize that it's the devices with the lightest color, a relatively small proportion of all tests, that should raise the suspicion that the amount of feces collected has been suboptimal. Inadequate collection of the fecal sample into the FIT collection device will result in a lower measured Hb concentration and potentially a false‐negative test result—and consequently a missed opportunity to detect some adenomas.”

Even though this study did not find any association of false‐negative results among patients with advanced adenomas or invasive colorectal cancer, it is possible that this problem might have been detected if a much larger number of patients had been studied. For this reason, “It's important that participants and patients are provided with simple instructions that highlight the importance of adequate fecal sample collection,” Dr. Symonds adds. “If resources permit it, the collection of two samples would assist in minimizing the risks.”

中文翻译：

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COVID 问题凸显了充足的粪便免疫化学测试样本收集的重要性

关键点

• 颜色最浅的粪便免疫化学测试 (FIT) 粪便样本的粪便血红蛋白 (Hb) 水平显着低于所有深色类别。
• 令人欣慰的是，无论 FIT 结果如何，在接受结肠镜检查的 467 名患者中，浅色样本并未对结直肠癌和晚期腺瘤产生更高的假阴性结果。

“重要的是……向患者提供了简单的说明，强调了充分收集粪便样本的重要性。”——Erin Symonds 博士

最近的调查表明，许多担心通过公众接触感染 2019 年冠状病毒病 (COVID-19) 的人一直在放弃癌症筛查测试。（例如，美国临床肿瘤学会发现，在大流行期间计划接受癌症筛查的人中，约有三分之二报告错过或延迟了筛查。）尽管粪便潜血测试，包括 FIT，可以在家为大多数此时担心进行结肠镜筛查的人提供了一个很好的解决方案，但之前的一些研究已经提出了患者的次优粪便收集可能会导致假阴性结果的担忧。

迄今为止，对分析前变量的大多数研究都集中在收集后发生的变量上，例如储存和环境温度以及分析前的时间滞后，导致粪便 Hb 降解，从而导致假阴性结果。然而，澳大利亚研究人员的一项新研究调查是否需要更加强调严格遵守粪便样本本身的收集，特别是收集的数量，以确保测试的诊断准确性。该研究发表于癌症流行病学、生物标志物和预防(doi:10.1158/1055-9965.EPI-20-0984)。

“这种类型的研究以前从未做过，”主要作者、弗林德斯医学中心高级研究科学家和团队负责人、贝德福德弗林德斯大学医学与公共卫生学院副教授 Erin Symonds 博士说帕克，南澳大利亚。“我们知道有几项研究调查了收集后变量对 FIT 性能的影响，但之前没有研究评估在临床环境中观察到的收集技术的变化。”

Symonds 博士说，她的团队认为，必须确定采样数量的不一致是否会影响发现晚期肿瘤和其他肠道疾病的临床结果，因为“使用 FIT 检测结直肠癌，无论是程序性筛查还是机会性筛查、监测或有症状的患者，依赖于 Hb 的准确测量来确定哪些人需要随访，通常是结肠镜检查。”

学习详情

研究人员检查了 FIT 设备（OC-Sensor；Eiken Chemical Co, Tokyo, Japan）由澳大利亚南部预防结直肠癌合作计划确定的高风险患者通过邮件返回实验室，该项目于 2000 年开发在澳大利亚国家健康和医学研究委员会发布大肠癌预防指南之后。参与者收到了 FIT 工具包，其中包括详细说明、2 个收集设备、2 个样本收集表以及一个带有回邮地址的小袋和信封。样本收集发生在 2019 年 1 月至 2020 年 2 月之间。

指示患者在家中从 2 种不同排便的粪便外表面收集样本。收集装置由用于采样粪便的圆周凹槽探针组成。正确执行收集后，将探针插入设备中，理想情况下大约 10 mg 粪便到达 2.0 mL 的 Hb 稳定缓冲液。

每个受试者都返回了两个设备。研究人员记录了第一次和第二次样品采集之间的天数，以及样品是在中午之前还是之后采集的。

在实验室收到样品后，在研究的前 4 个月内，由 2 名研究人员按照 1 到 5（从最浅到最深）的颜色分级，以在它们之间建立一致的评分。此外，大约 650 个收集装置在被送到患者之前被称重，然后在收集后返回实验室重新称重，以计算收集到的粪便的重量。最后，分析所有样品以确定粪便 Hb 水平。

研究结果

从 3449 个人收集了大约 6898 个样本。超过一半是女性（53.1%），所有受试者的中位年龄为 65.3 岁。其中，362件（5.2%）被评为颜色最浅，1836件（26.6%）被评为颜色2，2569件（37.2%）被评为颜色3，1711件（24.8%）被评为颜色3颜色 4 和 420 (6.1%) 的颜色最深（颜色 5）。

在 3449 个样本对中，858 个（24.9%）在第二个样本集合中颜色较深，872 个（25.3%）在第二个样本中颜色较浅；其余对被判断为相同颜色。对于回收的 650 个收集设备在样本收集前后记录了质量，收集的粪便质量中位数为 33.8 毫克。

研究人员发现颜色与样品质量显着相关：颜色 2、3、4 和 5 的质量明显大于分级为颜色 1 的质量 ( P = .002)。他们发现颜色最浅的样品与所有颜色较深的样品相比，粪便 Hb 水平显着降低 ( P < .001)。低样本质量与患者年龄、性别或其他人口统计变量无关。

在不考虑 FIT 结果而接受结肠镜检查的一部分研究参与者（467 名患者）的基础上，他们还确定粪便取样不足（颜色最浅的样品）与晚期肿瘤（结直肠癌和晚期肿瘤）的假阴性结果无关。腺瘤，后一类包括腺瘤，其大小和组织学表明进化为结直肠癌的风险更大），但用于结直肠肿瘤整体和炎症性肠病。对于颜色最浅的样本和所有其他颜色类别的样本，晚期肿瘤检测的假阴性百分比分别为 23.3% 和 22.8% ( P = .947)。

根据 Symonds 博士的说法，这项研究中最重要的发现是他们观察到“……那些浅色设备测得的粪便 Hb 浓度最低，FIT 阳性率最低，此外，浅色设备赋予了增加同时检测任何结直肠肿瘤和炎症性肠病时出现假阴性结果的风险。” 然而，研究结果提供了保证，即次优的粪便收集不太可能降低识别具有最临床相关病变（结直肠癌和腺瘤）的患者的敏感性，以便他们可以转诊进行诊断性结肠镜检查。

美国癌症协会的流行病筛查更新

除了担心某些患者在大流行期间可能会进入医院环境之外，亚特兰大美国癌症协会癌症控制干预措施前副总裁 Durado Brooks 医学博士、公共卫生硕士指出，几乎所有的卫生组织都劝阻内部, 去年冬天和春天的临床访问，这导致结直肠筛查数量显着下降。

布鲁克斯博士说，这就是患者可以在家进行的 FIT 等测试可以满足需求的地方——如果它们进行得正确的话。为此，全国结直肠癌圆桌会议创建了一个资源，题为“重新点燃结直肠癌筛查作为社区面对和应对 COVID-19 大流行：剧本”（nccrt.org/resource/a-playbook-for-reigniting-colorectal -癌症筛查作为社区应对covid-19大流行）。根据该联盟的说法，该文件包括最新的“与结直肠癌筛查和 COVID-19 相关的可用数据、研究和临床指南”，并为成员、合作伙伴和结直肠癌筛查倡导者如何“提供了一个以行动为导向的指南”共同努力，为所有社区适当、安全和平等地重新启动我们的筛查工作。”

关于自我筛查试剂盒，该手册指出，对于中等风险的人，可以在家安全地进行 FIT 或粪便 DNA 测试（例如 Cologuard）等测试。然而，美国癌症协会并不认为这些测试可以替代诊断性结肠镜检查。“如果粪便检测结果呈阳性，您将需要进行结肠镜检查，与您的医生讨论最安全的方法是很重要的。结肠镜检查作为筛查测试仍然是一种选择，但与 COVID-19 大流行之前相比，现在预约可能更难，”布鲁克斯博士说。

对于那些可以选择在家进行筛查的人，Symonds 博士强调了该研究结果对样本数量和颜色的重要性。“随着越来越多的人和临床医生鼓励 FIT 测试，实验室应该认识到它是颜色最浅的设备，在所有测试中所占的比例相对较小，这应该引起人们对收集的粪便量不理想的怀疑。将粪便样本收集到 FIT 收集装置中的不足将导致测得的 Hb 浓度降低，并可能出现假阴性检测结果，从而错失检测某些腺瘤的机会。”

尽管这项研究没有发现晚期腺瘤或浸润性结直肠癌患者的假阴性结果有任何关联，但如果研究了更多的患者，就有可能发现这个问题。出于这个原因，“重要的是向参与者和患者提供简单的说明，强调充分收集粪便样本的重要性，” Symonds 博士补充道。“如果资源允许，收集两个样本将有助于将风险降至最低。”