Evaluation of the optimum cut-off point in immunochemical occult blood testing in screening for colorectal cancer

This study was carried out to assess, from the aspects of cost-effectivenes s and diagnostic validity. the optimum cut-off point for immunochemical occ ult blood testing using a 2-day method as a means of screening for colorect al cancer. Four thousand, two hundred and sixty asymptomatic individuals we re subjects of this study. They gave samples for all immunochemical fecal o ccult blood test, and colonoscopy was carried out during a medical check-up . For evaluation of the optimum cut-off point, three cut-off levels of feca l haemoglobin, 50, 150 and 300 ng/ml, were used. A total of 27 patients wit h colorectal cancer were diagnosed. The average costs to detect one patient with colorectal cancer and the sensitivity and specificity of these three cut-off points of fecal haemoglobin were evaluated. The average costs for t he detection of one cancer case were calculated as $2870.45 for cut-off lev el of 50 ng/ml, $2492.98 for that of 150 ng/ml and $3329.09 for that of 300 ng/ml. respectively. The sensitivity and specificity were calculated as 89 and 94% for the 50 ng/ml cut-off level, 81% and 96% for the 150 ng/ml cut- off level and 56 and 97% for the 300 ng/ml cut-off level, respectively, ind icating a significant difference in the sensitivity between the 50 and 300 ng/ml levels (P < 0.05), as well as between the 150 and 300 ng/ml levels (P < 0.05), and a significant difference in the specificity between the 50 an d 300 ng/ml levels (P < 0.05). However, no significant difference was obser ved in the specificity between the 50 and 150 ng/ml levels. The findings sh ow that 150 ng/ml of fecal haemoglobin is the optimal cut-off point when ca rrying out the OC-Hemodia test as a means of screening for colorectal cance r. (C) 2001 Elsevier Science Ltd. All rights reserved.