Chen Li-Sheng, Liao Chao-Sheng, Chang Shu-Hui, Lai Hsin-Chih, Chen Tony Hsiu-Hsi
Division of Clinical Breast Cancer and Cancer Biology, Changhua Christian Hospital, 135 Nanhsiao Street, Changhua 500, Taiwan, ROC.
J Med Screen. 2007;14(4):191-9. doi: 10.1258/096914107782912022.
We aimed to determine the optimal cut-off of the immunochemical faecal occult blood test (iFOBT) by using cost-effectiveness analysis.
A total of 22,672 subjects aged 50 years or older were invited to have an uptake of iFOBT. We collected data from screen-detected cases for the cut-off above 100 ng/mL and obtained interval cancers from a nationwide cancer registry for a cut-off below 100 ng/mL. We found a total of 65 colorectal cancer (CRC) cases, including 43 detected by screen and 22 diagnosed between screens (interval cases). The optimal cut-off was first determined by receiver operating characteristics (ROC) curve analysis. Formal economic evaluation was further applied to identifying the optimal cut-off by assessing the minimum incremental cost-effectiveness ratio (ICER), an indicator for cost per life year gained (effectiveness), given a series of cut-offs of iFOBT, ranging from 30 to 200 ng/mL compared with no screening.
ROC curve analysis found the optimal cut-off of iFOBT to be 100 ng/mL at which the sensitivity, false-positive and odds of being affected given a positive result were 81.5% (70.2%-89.2%), 5.7% (5.4%-6.0%) and 1.24 (1.19-1.32), respectively. The area under ROC curve was 0.87 (0.81-0.93). In economic appraisal, the screening programme irrespective of any cut-off dominated (less cost and more effectiveness) over the control group. The optimal cut-off (the lowest ICER) was 110 ng/mL at which an average of 0.054 life year was gained and that of 950 ($US) was saved.
We used cost-effectiveness to identify 110 ng/mL as the optimal cut-off of iFOBT in a Taiwanese population-based screening for CRC. Our model provides a useful approach for health policy-makers in designing population-based screening for CRC to determine the optimal cut-off of iFOBT when cost and effectiveness need to be taken into account.
我们旨在通过成本效益分析确定免疫化学粪便潜血试验（iFOBT）的最佳临界值。
共邀请了22672名50岁及以上的受试者接受iFOBT检测。我们收集了筛查发现的临界值高于100 ng/mL的病例数据，并从全国癌症登记处获取了临界值低于100 ng/mL的间期癌病例数据。我们共发现65例结直肠癌（CRC）病例，其中43例通过筛查发现，22例在两次筛查之间确诊（间期病例）。首先通过受试者工作特征（ROC）曲线分析确定最佳临界值。进一步进行正式的经济评估，通过评估最小增量成本效益比（ICER）来确定最佳临界值，ICER是每获得一个生命年（效益）的成本指标，在一系列iFOBT临界值（范围为30至200 ng/mL）与未进行筛查的情况进行比较。
ROC曲线分析发现iFOBT的最佳临界值为100 ng/mL，此时敏感性、假阳性率以及阳性结果时受影响的几率分别为81.5%（70.2%-89.2%）、5.7%（5.4%-6.0%）和1.24（1.19-1.32）。ROC曲线下面积为0.87（0.81-0.93）。在经济评估中，无论临界值如何，筛查方案均优于对照组（成本更低且效益更高）。最佳临界值（最低ICER）为110 ng/mL，此时平均可获得0.054个生命年，并节省950美元。
我们利用成本效益分析确定110 ng/mL为台湾地区基于人群的CRC筛查中iFOBT的最佳临界值。我们的模型为卫生政策制定者在设计基于人群的CRC筛查时提供了一种有用的方法，以便在需要考虑成本和效益时确定iFOBT的最佳临界值。
