Division of Preventive Oncology, German Cancer Research Center, and National Center for Tumor Diseases, Heidelberg, Germany; Medical Faculty Heidelberg, University of Heidelberg, Heidelberg, Germany.
Medical Faculty Heidelberg, University of Heidelberg, Heidelberg, Germany; Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, and National Center for Tumor Diseases, Heidelberg, Germany.
Clin Gastroenterol Hepatol. 2019 Aug;17(9):1829-1839.e4. doi: 10.1016/j.cgh.2019.03.001. Epub 2019 Mar 6.
BACKGROUND & AIMS: Fecal immunochemical tests (FITs) measure hemoglobin in stool to identify individuals at risk for colorectal cancer (CRC). However, there are many different FITs, with different instructions for fecal sample collection. In routine practice, participants do not always follow these instructions exactly. We assessed the effects of violations of fecal sampling instructions on the diagnostic performance of 9 quantitative FITs.
We obtained stool samples from 76 patients with CRC scheduled for surgery at 4 hospitals in Germany and 100 participants without advanced neoplasms who participated in a prospective colonoscopy screening program. We filled fecal sample tubes according to the manufacturers' instructions or with 3 violations that are likely to occur in routine practice. The diagnostic performance was assessed for a total of 6336 FIT samples (176 participants × 9 FITs × 4 sampling methods).
Sample collection instructions varied widely among FITs but included 3 key components: multiple insertions of the sampling rod into stool, a visual check of rod for complete filling with stool, and once-only insertion of the stool-filled rod into the tube. Violation of the first 2 components (inserting the rod into the stool sample only 1 time or not visually checking the rod for complete filling) reduced levels of hemoglobin measured. However, the effect on diagnostic performance was generally small. Violation of the third component (insertion of more stool into the tube than recommended) increased levels of hemoglobin measured in samples and identified more patients with CRC (increase of median sensitivity by almost 10% units) at a small loss of specificity (decrease of median specificity by 2% units), and produced the highest area under the curve for detection of CRC cases for 6 FITs.
Violations of fecal sampling instructions can lead to non-negligible variations in fecal hemoglobin measurements. The limited adverse effects on diagnostic performance indicate the robustness of FITs. The potential for increasing diagnostic performance by collecting more stool material should be followed up in further research.
粪便免疫化学检测（FIT）通过检测粪便中的血红蛋白来识别结直肠癌（CRC）高危人群。然而，有许多不同的 FIT，其粪便样本采集的说明也有所不同。在常规实践中，参与者并不总是完全遵循这些说明。我们评估了粪便采样说明的违反情况对 9 种定量 FIT 的诊断性能的影响。
我们从德国 4 家医院计划手术的 76 名 CRC 患者和 100 名未患有晚期肿瘤的参加前瞻性结肠镜筛查计划的参与者中获得了粪便样本。我们按照制造商的说明或可能在常规实践中发生的 3 种违规行为来填充粪便样本管。我们共评估了 6336 个 FIT 样本（176 名参与者×9 种 FIT×4 种采样方法）的诊断性能。
FIT 之间的采样说明差异很大，但包括 3 个关键组成部分：多次将采样棒插入粪便中、目视检查棒是否完全填满粪便，以及仅将充满粪便的棒一次性插入管中。违反前两个组成部分（仅将棒插入粪便样本一次或不目视检查棒是否完全填满）会降低测量的血红蛋白水平。然而，对诊断性能的影响通常较小。违反第三个组成部分（将比推荐量更多的粪便插入管中）会增加样本中测量的血红蛋白水平，并识别出更多的 CRC 患者（敏感性中位数增加近 10%单位），特异性损失较小（特异性中位数下降 2%单位），并且对 6 种 FIT 的 CRC 病例检测产生了最高的曲线下面积。
粪便采样说明的违反会导致粪便中血红蛋白测量值出现不可忽略的变化。对诊断性能的有限不利影响表明 FIT 具有稳健性。通过收集更多的粪便样本材料来提高诊断性能的潜力应该在进一步的研究中进行跟踪。
