Analysis of Guaiac-based Fecal Occult Blood Test Occult blood was detected in the feces of 29.4% (5/17) of healthy subjects and 68.2% (15/22) of CRC patients. Thus, the specificity and sensitivity of gFOBT for CRC was 70.6% (95% confidence intervals 44% to 89.7%) and 68.2% (95% confidence intervals merely 45.1% to 86.1%, respectively. A nearly significantly (p=0.09) higher proportion of left-sided CRC (83.3%; 10/12) showed gFOBT positivity compared to right-sided CRC (50%; 5/10) (Table 2, ,33). Analysis of Carcinoembryonic Antigen Serum Level In the case of CEA, two groups were defined: one with elevated CEA serum levels and the other with normal levels. In our study, 14.8% (4/27) of the healthy subjects had elevated CEA levels, while only 51.8% (14/27) of the CRC specimens showed elevated levels.

Thus, the specificity and sensitivity of CEA for CRC was 85.2% (95% confidence intervals 66.3% to 95.8%) and 51.8% (95% confidence intervals 31.9% to 71.3%), respectively. There was no significant difference (p=0.34) between the proportion of left-sided CRC cases (9/15, 60%) and right-sided CRC cases (5/12, 41.6%) with elevated CEA serum levels (Tables 2, ,33). Discussion CRC screening to identify tumors at early stages reduces the mortality of the disease. However, the highly sensitive and specific screening methods (i.e. colonoscopy and CT enterography) are invasive and patient compliance is low. On the other hand, other methods that are not as invasive (i.e., FOBT and CEA) have low specificity and sensitivity. Therefore, a suitable screening method with minimal invasiveness is needed.

In this study, we compared the sensitivity and specificity of methylated Septin 9 as a colorectal biomarker in serum to both gFOBT and CEA serum level. We performed the analysis of gFOBT testing retrospectively for both healthy controls and CRC patients. The 68.2% sensitivity of gFOBT for CRC in our study correlates to previously published results [3] and the specificity of gFOBT for CRC reached 70.6%. While this method has been used for CRC screening for several decades, it has poor sensitivity due to its non-specificity for gastrointestinal bleeding. It has been shown to reduce both CRC incidence and mortality by 15�C33%. However, testing once is not sufficient, so repeated testing is needed, and in the case of positivity, GSK-3 colonoscopy is recommended. Unfortunately, notable numbers of patients refuse both the repeated gFOBT and the suggested colonoscopy [21]. In our study, occult blood detection from stool was performed only once for each case and gFOBT showed 29.4% (5/17) positivity in the healthy group. However, subsequent colonoscopy did not find any sign of neoplasia or polyps in these cases.