Relationship between fecal sampling times and sensitivity and specificity of immunochemical fecal occult blood tests for colorectal cancer: a comparative study.

Abstract

The present study was conducted to assess the accuracy of three testing methods using an immunochemical fecal occult blood test based on the number of samples as the optimum means for screening of colorectal cancer. One hundred eighty-four patients with colorectal cancer and 368 healthy controls served as the subjects for this study. Each subject was tested by an immunochemical fecal occult blood test for three consecutive days. For evaluation of the most desirable number of sampling times, we used the results of the first day for the one-day method, results of the first and second days for the two-day method, and results of three consecutive days for the three-day method. Sensitivities and specificities of the three testing methods were evaluated. Sensitivities of an immunochemical fecal occult blood test were calculated as 67.9 percent for the one-day method, 88 percent for the two-day method, and 90.8 percent for the three-day method; specificity was as follows: 97.5 percent for the one-day method, 95.6 percent for the two-day method, and 92.1 percent for the three-day method. A significant difference in sensitivity was shown between the one-day and two-day and the one-day and three-day methods (P < 0.01); also, a significant difference in specificity was shown between one-day and three-day and two-day and three-day methods (P <0.05). These results indicate that the two-day method is recommended for immunochemical fecal occult blood testing as a means of screening for colorectal cancer.