Department of Gastroenterology and Hepatology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, the Netherlands.
Cancer Epidemiol Biomarkers Prev. 2011 Feb;20(2):272-80. doi: 10.1158/1055-9965.EPI-10-0848. Epub 2010 Dec 6.
Adjusting the threshold for positivity of quantitative fecal immunochemical tests (FIT) allows for controlling the number of follow-up colonoscopies in a screening program. However, it is unknown to what extent higher cutoff levels affect detection rates of screen-relevant neoplasia. This study aimed to assess the effect of higher cutoff levels of a quantitative FIT on test positivity rate and detection rate of early-stage colorectal cancers (CRC).
Subjects above 40 years old scheduled for colonoscopy in 5 hospitals were asked to sample a single FIT (OC sensor) before colonoscopy. Screen-relevant neoplasia were defined as advanced adenoma or early-stage cancer (stage I and II). Positivity rate, sensitivity, and specificity were evaluated at increasing cutoff levels of 50 to 200 ng/mL.
In 2,145 individuals who underwent total colonoscopy, 79 patients were diagnosed with CRC, 38 of which were with early-stage disease. Advanced adenomas were found in 236 patients. When varying cutoff levels from ≥ 50 to ≥ 200 ng/mL, positivity rates ranged from 16.5% to 10.2%. With increasing cutoff levels, sensitivity for early-stage CRCs and for screen-relevant neoplasia ranged from 84.2% to 78.9% and 47.1% to 37.2%, respectively.
Higher FIT cutoff levels substantially decrease test positivity rates with only limited effects on detection rates of early-stage CRCs. However, spectrum bias resulting in higher estimates of sensitivity than would be expected in a screening population may be present.
Higher cutoff levels can reduce strain on colonoscopy capacity with only a modest decrease in sensitivity for curable cancers.
调整定量粪便免疫化学检测（FIT）的阳性阈值可以控制筛查计划中后续结肠镜检查的数量。然而，尚不清楚更高的截止值在多大程度上影响筛查相关肿瘤的检出率。本研究旨在评估定量 FIT 的更高截止值对早期结直肠癌（CRC）检测的阳性率和检出率的影响。
在 5 家医院预约结肠镜检查的 40 岁以上的受试者被要求在结肠镜检查前采集单次 FIT（OC 传感器）样本。筛查相关的肿瘤定义为高级腺瘤或早期癌症（I 期和 II 期）。在 50 至 200ng/ml 的递增截止值下评估阳性率、敏感性和特异性。
在 2145 名接受全结肠镜检查的患者中，79 名被诊断为 CRC，其中 38 名处于早期阶段。236 名患者发现高级腺瘤。当截止值从≥50 至≥200ng/ml 时，阳性率从 16.5%降至 10.2%。随着截止值的升高，早期 CRC 和筛查相关肿瘤的敏感性分别从 84.2%降至 78.9%和从 47.1%降至 37.2%。
更高的 FIT 截止值会大大降低检测的阳性率，而对早期 CRC 的检出率影响有限。然而，可能存在导致敏感性估计值高于筛查人群的谱偏倚。
更高的截止值可以减少结肠镜检查能力的压力，同时对可治愈癌症的敏感性只有适度下降。
