Evaluation Of Quantitative Immunochemical Fecal Occult Blood Test For The Diagnosis Of Colorectal Cancer And Other Gastrointestinal Diseases

[Objectives] To investigate the clinical value of the quantitative immunochemical fecal occult blood test(QIFOBT) for colorectal cancer(CRC) and other gastrointestinal diseases.[Matheds] Outpatients (from November 2008 to February 2010) who were going to undergo gastroscopy and colonoscopy and inpatients with final diagnosis of CRC who were going to undergo surgical operation simultaneously accepted the QIFOBT and the colloidal gold immunochromatographic FOBT(CGIFOBT) for research purposes. (1) The total number of samples was 502 including 101 patients with CRC(82 inpatients and 19 outpatients) and 401 outpatients with non-colorectal cancer. The diagnosis value in CRC and non-colorectal cancer of the two methods were compared and evaluated. (2) We compared the diagnosis rates of the QIFOBT with CT scan and DCBE(double-contrast barium enema) and CEA(carcinoembryonic antigen). (3) We investigated whether the QIFOBT was associated with the Dukes Staging or the size of CRC. (4) We performed a preliminary analysis of the diagnositic positive rates of the QIFOBT for CRC at different positive threshold.[Results] (1) The total positive rates of the QIFOBT and the CQIFOBT in all the 502 patients were 35% and 21%(P<0.05) respectively, while the false positive rates were 1.9% and 3.7%(P>0.05), and the positive rates in CRC were 93.4% and 63.2% (P<0.05) respectively. The total positive rates of the QIFOBT and the GIFOBT for the 420 outpatients were 16.1% and 7.2%(P<0.05). No statistical differences were found between the QIFOBT and the CGIFOBT in each disease of the outpatients (P>0.05). The positive rates of the QIFOBT for CRC and non-colorectal cancer were 92.1% and 15.4%(P<0.05) respectively. The positive rates of the QIFOBT for the upper gastrointestinal diseases and lower gastrointestinal diseases were 13.1% and 26.8%(P＜0.05), and for the colorectal polyps with≥1cm and＜1cm were 29.4% and 5.3%(P<0.05) respectively. (2) The positive rates of the QIFOBT and CEA for the colorectal cancer were 93.8% and 73.4% respectively (P＜0.05). The positive rates of the QIFOBT and DCBE were 84.6% and 100%(P>0.05), and CT scan were 97.3% and 97.3%, respectively (P>0.05). (3) The QIFOBT was not significantly associated with the Dukes Staging of the CRC (P>0.05), whereas has direct correlation with the size of CRC (P<0.05). (4) Compared with 100 ng/mL, the positive rates of CRC and the normal large intestine(normal appearance of colorectal mucosa) will increase by 2% and 4.6% when the positive threshold of the QIFOBT is at 50 ng/mL, and it will decrease by 3% and 0.9% at 150ng/mL, by 5% and 0.9% at 200ng/mL, respectively.[Conclusions] (1) Compared with the CGIFOBT and serum tumor markers (such as CEA), the QIFOBT has a significantly higher positive rate (>90%) and a comparable diagnosis value with CT scan and DCBE for CRC. (2) The QIFOBT has more high sensibility in the diagnosis of the lower gastrointestinal diseases than that of the upper gastrointestinal diseases, and the positive rate of the QIFOBT for CRC is associated with the size of the colorectal polyp. (3) The positive threshold of the QIFOBT can affect the detection rate in the diagonsis of CRC, and the threshold at 100 ng/mL has the most optimum positive rate and false positive rate for the diagnosis of CRC. (4) The QIFOBT has a direct correlation with the size of the CRC, while the correlation between the QIFOBT and the Dukes Staging of the CRC should be further determined.