A Comparison of the Immunochemical Fecal Occult Blood Test and Total Colonoscopy in the Asymptomatic Population
2005; Elsevier BV; Volume: 129; Issue: 2 Linguagem: Inglês
10.1053/j.gastro.2005.05.056
ISSN1528-0012
AutoresTamiya Morikawa, Jun Kato, Yutaka Yamaji, Ryoichi Wada, Toru Mitsushima, Yasushi Shiratori,
Tópico(s)Genetic factors in colorectal cancer
ResumoBackground & Aims: The fecal occult blood test (FOBT) is recommended as a screening test for colorectal cancer, but there are few reliable studies on the accuracy of immunochemical FOBT. The aim of this study was to analyze the sensitivity of immunochemical FOBT and to compare the results with the findings from complete colonoscopy. Methods: Asymptomatic adults underwent 1-time immunochemical FOBT and total colonoscopy simultaneously. The prevalence and location of colorectal neoplasia were determined by colonoscopy. The results of immunochemical FOBT and the colonoscopic findings were compared. Results: Of 21,805 patients, immunochemical FOBT was positive in 1231 cases (5.6%). The sensitivity of 1-time immunochemical FOBT for detecting advanced neoplasia and invasive cancer was 27.1% and 65.8%, respectively. In addition, the sensitivity for invasive cancer according to Dukes’ stage showed 50.0% for Dukes’ stage A, 70.0% for Dukes’ stage B, and 78.3% for Dukes’ stages C or D. The sensitivity for detecting advanced neoplasia at the proximal colon was significantly lower than that detected in the distal colon (16.3% vs 30.7%, P = .00007). Conclusions: Although the screening of asymptomatic patients with immunochemical FOBT can identify patients with colorectal neoplasia to a certain extent, the sensitivity is relatively low and different according to the tumor location. Therefore, programmatic and repeated screening by immunochemical FOBT may be necessary to increase sensitivity for colorectal cancer detection. Background & Aims: The fecal occult blood test (FOBT) is recommended as a screening test for colorectal cancer, but there are few reliable studies on the accuracy of immunochemical FOBT. The aim of this study was to analyze the sensitivity of immunochemical FOBT and to compare the results with the findings from complete colonoscopy. Methods: Asymptomatic adults underwent 1-time immunochemical FOBT and total colonoscopy simultaneously. The prevalence and location of colorectal neoplasia were determined by colonoscopy. The results of immunochemical FOBT and the colonoscopic findings were compared. Results: Of 21,805 patients, immunochemical FOBT was positive in 1231 cases (5.6%). The sensitivity of 1-time immunochemical FOBT for detecting advanced neoplasia and invasive cancer was 27.1% and 65.8%, respectively. In addition, the sensitivity for invasive cancer according to Dukes’ stage showed 50.0% for Dukes’ stage A, 70.0% for Dukes’ stage B, and 78.3% for Dukes’ stages C or D. The sensitivity for detecting advanced neoplasia at the proximal colon was significantly lower than that detected in the distal colon (16.3% vs 30.7%, P = .00007). Conclusions: Although the screening of asymptomatic patients with immunochemical FOBT can identify patients with colorectal neoplasia to a certain extent, the sensitivity is relatively low and different according to the tumor location. Therefore, programmatic and repeated screening by immunochemical FOBT may be necessary to increase sensitivity for colorectal cancer detection. Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in Japan, and the incidence of CRC has increased significantly over the past decade. A survey conducted by the Japanese Ministry of Health, Labour, and Welfare found that an estimated 37,000 Japanese died of the disease in 2001. The fecal occult blood test (FOBT) has been recommended widely as a screening test for CRC. Three randomized controlled clinical trials showed that FOBT reduced the risk for death from CRC 1Mandel J.S. Bond J.H. Church T.R. Snover D.C. Bradley G.M. Schuman L.M. Ederer F. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study.N Engl J Med. 1993; 328: 1365-1371Crossref PubMed Scopus (2925) Google Scholar, 2Hardcastle J.D. Chamberlain J.O. Robinson M.H. Moss S.M. Amar S.S. Balfour T.W. James P.D. Mangham C.M. Randomized controlled trial of faecal-occult-blood screening for colorectal cancer.Lancet. 1996; 348: 1472-1477Abstract Full Text Full Text PDF PubMed Scopus (2444) Google Scholar, 3Kronborg O. Fenger C. Olsen J. Jorgensen O.D. Sondergaard O. Randomized study of screening for colorectal cancer with feacal-occult-blood test.Lancet. 1996; 348: 1467-1471Abstract Full Text Full Text PDF PubMed Scopus (2194) Google Scholar because of the earlier detection and hence surgical removal of the CRC. In Japan, immunochemical FOBT, the sensitivity of which is reported to be higher than that of the guaiac-based FOBT, generally is used for CRC screening. 4St John D.J. Young G.P. Alexeyeff M.A. Deacon M.C. Cuthbertson A.M. Macrae F.A. Penfold J.C. Evaluation of new occult blood tests for detection of colorectal neoplasia.Gastroenterology. 1993; 104: 1661-1668PubMed Google Scholar, 5Allison J.E. Tekawa I.S. Ransom L.J. Adrain A.L. A comparison of fecal occult-blood tests for colorectal-cancer screening.N Engl J Med. 1996; 334: 155-159Crossref PubMed Scopus (531) Google Scholar, 6Castiglione G. Zappa M. Grazzini G. Mazzotta A. Biagini M. Salvadori P. Ciatto S. Immunochemical vs guaiac faecal occult blood tests in a population-based screening programme for colorectal cancer.Br J Cancer. 1996; 74: 141-144Crossref PubMed Scopus (77) Google Scholar However, FOBT displays low sensitivity for detecting CRC (sensitivity range, 26%–69%). 5Allison J.E. Tekawa I.S. Ransom L.J. Adrain A.L. A comparison of fecal occult-blood tests for colorectal-cancer screening.N Engl J Med. 1996; 334: 155-159Crossref PubMed Scopus (531) Google Scholar, 7Allison J.E. Feldman R. Tekawa I.S. Hemoccult screening in detecting colorectal neoplasm: sensitivity, specificity, and predictive value: long-term follow-up in a large group practice setting.Ann Intern Med. 1990; 112: 328-333Crossref PubMed Scopus (124) Google Scholar, 8Ahlquist D.A. Wieand H.S. Moertel C.G. McGill D.B. Loprinzi C.L. O’Connell M.J. Mailliard J.A. Gerstner J.B. Pandya K. Ellefson R.D. Accuracy of fecal occult blood screening for colorectal neoplasia a prospective study using Hemoccult and HemoQuant tests.JAMA. 1993; 269: 1261-1267Crossref Scopus (309) Google Scholar, 9Lieberman D.A. Weiss D.G. Veterans Affairs Cooperative Study Group 380One-time screening for colorectal cancer with combined fecal occult-blood testing and examination of the distal colon.N Engl J Med. 2001; 345: 555-560Crossref PubMed Scopus (531) Google Scholar Moreover, the sensitivity of FOBT for detecting adenomas is much lower, with results ranging from 9% to 36%. 7Allison J.E. Feldman R. Tekawa I.S. Hemoccult screening in detecting colorectal neoplasm: sensitivity, specificity, and predictive value: long-term follow-up in a large group practice setting.Ann Intern Med. 1990; 112: 328-333Crossref PubMed Scopus (124) Google Scholar, 8Ahlquist D.A. Wieand H.S. Moertel C.G. McGill D.B. Loprinzi C.L. O’Connell M.J. Mailliard J.A. Gerstner J.B. Pandya K. Ellefson R.D. Accuracy of fecal occult blood screening for colorectal neoplasia a prospective study using Hemoccult and HemoQuant tests.JAMA. 1993; 269: 1261-1267Crossref Scopus (309) Google Scholar, 9Lieberman D.A. Weiss D.G. Veterans Affairs Cooperative Study Group 380One-time screening for colorectal cancer with combined fecal occult-blood testing and examination of the distal colon.N Engl J Med. 2001; 345: 555-560Crossref PubMed Scopus (531) Google Scholar, 10Macrae F.A. St John D.J. Relationship between patterns of bleeding and Hemoccult sensitivity in patients with colorectal cancers of adenomas.Gastroenterology. 1982; 82: 891-898Abstract Full Text PDF PubMed Scopus (250) Google Scholar, 11Crowley M.L. Freeman L.D. Mottet M.D. Strong R.M. Sweeney B.F. Brower R.A. Sharma S.P. Anderson D.S. Sensitivity of guaiac-impregnated cards for the detection of colorectal neoplasia.J Clin Gastroenterol. 1983; 5: 127-130Crossref PubMed Scopus (47) Google Scholar, 12Rozen P. Knaani J. Samuel Z. Comparative screening with a sensitive guaiac and specific immunochemical occult blood test in an endoscopic study.Cancer. 2000; 89: 46-52Crossref PubMed Scopus (47) Google Scholar Therefore, annual testing by FOBT is recommended to reduce the risk for death from CRC. 1Mandel J.S. Bond J.H. Church T.R. Snover D.C. Bradley G.M. Schuman L.M. Ederer F. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study.N Engl J Med. 1993; 328: 1365-1371Crossref PubMed Scopus (2925) Google Scholar Recent reports have started to recommend colonoscopy as a primary screening test for CRC. 13Lieberman D.A. Weiss D.G. Bond J.H. Ahnen D.J. Veterans Affairs Cooperative Study Group 380Use of colonoscopy to screen asymptomatic adults for colorectal cancer.N Engl J Med. 2000; 343: 162-168Crossref PubMed Scopus (1621) Google Scholar, 14Imperiale T. Wagner D. Lin C. Larkin G. Roge J. Ransohoff D. Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings.N Engl J Med. 2000; 343: 169-174Crossref PubMed Scopus (925) Google Scholar, 15Podolsky D. Going the distance the case for true colorectal-cancer screening.N Engl J Med. 2000; 343: 207-208Crossref PubMed Scopus (144) Google Scholar, 16Sonnenberg A. Delco F. Inadomi J. Cost-effectiveness of colonoscopy in screening for colorectal cancer.Ann Intern Med. 2000; 133: 573-584Crossref PubMed Scopus (443) Google Scholar, 17Lewis J.D. Prevention and treatment of colorectal cancer pay now or pay later.Ann Intern Med. 2000; 133: 647-649Crossref PubMed Scopus (18) Google Scholar, 18Sung J.J.Y. Chan F.K.L. Leung W.K. Wu J.C.Y. Lau J.Y.W. Ching J. To K.F. Lee Y.T. Luk Y.W. Kung N.N.S. Kwok S.P.Y. Li M.K.W. Chung S.C.S. Screening for colorectal cancer in Chinese comparison of fecal occult blood test, flexible sigmoidoscopy, and colonoscopy.Gastroenterology. 2003; 124: 608-614Abstract Full Text Full Text PDF PubMed Scopus (153) Google Scholar Colonoscopy seems to be the most accurate test for this purpose and it can be used to remove polyps and early cancers. Furthermore, negative findings on colonoscopic examination can obviate the need for further screening for 5 years or longer. 15Podolsky D. Going the distance the case for true colorectal-cancer screening.N Engl J Med. 2000; 343: 207-208Crossref PubMed Scopus (144) Google Scholar Although colonoscopy is an expensive examination that requires highly skilled endoscopists, it often is used as a screening test in Japan. In this study, we simultaneously performed total colonoscopy and immunochemical FOBT in the asymptomatic population. Next, we analyzed the sensitivity and specificity of immunochemical FOBT. Moreover, we examined the prevalence and location of colonic neoplasia by conducting complete colonoscopy in a large group of asymptomatic patients in Japan. A committee at Kameda General Hospital approved this study protocol consisting of a retrospective analysis of an existing dataset from patients who participated in a comprehensive health examination program at Kameda General Hospital or Kameda Makuhari Clinic between April 1983 and March 2002. All patients completed a questionnaire designed to examine whether they had any symptoms and what kinds of symptoms they had. Patients were excluded if they reported symptoms of disease of the lower gastrointestinal tract including visible rectal bleeding, recent change in bowel habits, or lower abdominal pain that normally would require a medical evaluation. Of these participants, we consecutively enrolled 22,666 persons who simultaneously underwent colonoscopy and immunochemical FOBT. All eligible patients were asymptomatic and participated voluntarily in this program. Information on family history with respect to CRC and the results of prior screening or diagnostic colorectal evaluations, in general, were not requested or recorded routinely. We performed a 1-day immunochemical FOBT. Participants were asked to prepare a fecal sample from a stool specimen by using the collection kit provided by the manufacturer (Fujirebio Inc, Tokyo, Japan). The participants received collection kits about 2 weeks before the scheduled colonoscopy. The day before the colonoscopy (or in the morning on the day of the colonoscopy), patients collected stool samples themselves, keeping the sample dry during collection (without touching the water in the toilet bowl). Participants brought the collection tubes to the hospital or clinic on the day of the colonoscopy and the stool samples were sent to the laboratory within 24 hours and tested immediately. We used the Magstream 1000/Hem SP automated system (Fujirebio) for immunochemical FOBT. This system evolved from the Immudia-Hem SP test (Fujirebio), which was the original version of HemeSelect (Beckman Coulter, Palo Alto, CA). Details of the Magstream 1000/Hem SP system have been described in a previous study by Wong et al. 19Wong W.M. Lam S.K. Cheung K.L. Tong T.S. Rozen P. Young G.P. Chu K.W. Ho J. Law W.L. Tung H.M. Choi H.K. Lee Y.M. Lai K.C. Hu W.H. Chan C.K. Yuen M.F. Wong B.C. Evaluation of an automated immunochemical fecal occult blood test for colorectal neoplasia detection in a Chinese population.Cancer. 2003; 97: 2420-2424Crossref PubMed Scopus (56) Google Scholar In brief, the hemagglutination technique using chicken red cells in the Immudia-Hem SP test was replaced by magnetically induced agglutination, which was made possible by the attachment of rabbit antibodies against human hemoglobin to particles of gelatin containing ferrite and gum arabic. This modification led to faster agglutination and produced a more stable agglutinate, which allowed for an automated result interpretation by the Magstream 1000 instrument. The Magstream system had a sensitivity of 20 mg hemoglobin/L or .1–.2 mg hemoglobin per gram of feces. On the day of the colonoscopy, patients received 2 L of a polyethylene glycol-based electrolyte solution for bowel preparation according to the instructions for use (Ajinomoto Pharma, Tokyo, Japan). After the colonic lavage was finished, patients underwent the colonoscopy. Qualified gastroenterologists practicing at Kameda General Hospital or Kameda Makuhari Clinic performed the colonoscopy. In all cases the endoscopists were blinded to the results of FOBT. For the procedure, a standard commercial video colonoscope (PCF-200, PCF-230, or PCF-240; Olympus, Tokyo, Japan) was inserted into the cecum. Sedatives rarely were used during the colonoscopic examination. Patients were excluded if the colonoscopic examination was incomplete because of problems with bowel preparation or failed colonoscope insertion into the cecum. If a colonoscopic examination was incomplete because of obstructing tumors, the endoscopist’s best estimate of the depth of inspection was recorded, and these results were included in the analysis. During the colonoscopy, the location and size of all polypoid lesions were determined before their removal from the colon and were recorded by the endoscopists. If a patient had more than 1 polyp, the most advanced pathologic lesion or the largest lesion was included in the analysis. In addition, we regarded the pathologic findings as taking precedence over size. For example, if a patient had both an adenoma 10 mm or larger and an adenoma with high-grade dysplasia 9 mm or smaller, the patient was regarded as having an adenoma with high-grade dysplasia. Endoscopists used biopsy forceps as a visual guide to estimate the size of the polyps. Polyps measuring 4–5 mm or more in diameter were subjected to polypectomy by diathermy snare after the completion of the study during second-look colonoscopy, whereas tissue specimens from smaller polyps were obtained with cold biopsy forceps during screening colonoscopy conducted at the time of this study. All patients who were diagnosed with invasive cancer underwent surgical treatment. When we examined the sensitivity of immunochemical FOBT according to the location of neoplasia, the distal colon included the descending colon, sigmoid colon, and rectum, whereas the proximal colon included the transverse colon, ascending colon, and cecum. Patients who had advanced neoplasia both in the proximal and distal colon were excluded from the analysis on the sensitivity and specificity of advanced neoplasia according to the location. Polyps removed by biopsy procedure or polypectomy and invasive cancer that was treated surgically were fixed in formaldehyde for routine histologic examination. All retrieved polypoid lesions were sent to the pathology laboratory for histologic evaluation and classified in accordance with the World Health Organization classification. Two pathologists interpreted the histopathologic features and when there was a disagreement a third pathologist reviewed the features. Histologic characteristics of polyps included normal mucosa, hyperplastic polyps, and adenoma (tubular, tubulovillous, or villous). Hyperplastic polyps were not included as neoplasia. Advanced colonic neoplasia was defined as adenomas 10 mm or more in diameter, adenomas with high-grade dysplasia, or invasive cancer. Intramucosal carcinoma and carcinoma in situ were classified as adenoma with high-grade dysplasia. The criterion for diagnosing cancer was an invasion of malignant cells beyond the muscularis mucosa. Database management and all statistical analyses were performed with SAS software (SAS Institute, Cary, NC). We used the χ2 test for a comparison of proportions. Relative risks with 95% confidence intervals were calculated to estimate the differences between positive FOBT and negative FOBT results for neoplasia. A 2-tailed P value of less than .05 was considered statistically significant. Of the 22,666 participants enrolled in this study, a complete colonoscopy was performed in 22,259 patients (98.2%), and 407 patients were excluded because of an incomplete colonoscopy. There were no serious complications during or after the colonoscopy. Patients lacking sufficient information on the polypoid lesion (location, size, or pathologic findings) also were excluded (n = 454). In the end, we analyzed 21,805 patients, comprising 15,694 men and 6111 women, with a mean age of 48.2 ± 9.3 years (range, 20–91 y). Immunochemical FOBT was positive in 1231 patients (5.6%), and negative in 20,574 patients (94.4%). As shown in Table 1, there were no significant differences in population characteristics between all enrolled patients and eligible patients. Of all the eligible patients, invasive cancer was detected in 79 patients (.4%). Of these cancer patients, 36 patients were classified as Dukes’ stage A, 10 patients as Dukes’ stage B, and 23 patients as Dukes’ stages C or D. Sufficient information for the remaining 10 patients was not available to determine the stage. Advanced neoplasia including adenomas 10 mm or larger, adenomas with high-grade dysplasia, and invasive cancer were seen in 727 patients (3.3%) (Table 1).Table 1Characteristics of Study PopulationVariableNumber of patients (%)Patients at enrollment (n = 22,666)Eligible patients (n = 21,805)Sex Male16,290 (71.9)15,694 (72.0) Female6376 (28.1)6111 (28.0)Age Mean ± SD, y48.3 ± 9.448.2 ± 9.3 <404197 (18.5)4089 (18.8) 40–498882 (39.2)8607 (39.5) 50–596936 (30.6)6640 (30.5) 60–692262 (10.0)2116 (9.7) ≥70389 (1.7)353 (1.6)FOBT Positive1294 (5.7)1231 (5.6) Negative21,372 (94.3)20,574 (94.4)Finding No neoplasia17,480 (80.2) Adenoma ≤ 9 mm aExcept adenomas with high-grade dysplasia.3598 (16.5) Advanced neoplasia727 (3.3) Adenoma ≥ 10 mm aExcept adenomas with high-grade dysplasia.529 (2.4) High-grade dysplasia119 (0.5) Invasive cancer79 (0.4) Dukes’ stage A36 Dukes’ stage B10 Dukes’ stages C or D23 Unknown10a Except adenomas with high-grade dysplasia. Open table in a new tab We calculated the sensitivity and specificity of immunochemical FOBT according to colonoscopic findings (Table 2). Although the sensitivity for detecting neoplasia increased as the histologic stage progressed, even the sensitivity for detecting invasive cancer was only 65.8%. One-time immunochemical FOBT failed to detect one third of the patients with invasive cancer. In addition, the sensitivity for invasive cancer according to Dukes’ stage proved to be 52.8% for Dukes’ stage A, 70.0% for Dukes’ stage B, and 78.3% for Dukes’ stages C or D. Thus, in our study, immunochemical FOBT was less sensitive for detecting localized cancer than advanced cancer.Table 2Results of Immunochemical FOBT and Colonoscopic FindingsNo neoplasiaNeoplasiaAdvanced neoplasiaTotalAdenoma ≥10 mm aExcept adenomas with high-grade dysplasia.High-grade dysplasiaInvasive cancerTotalDukes’ stage ADukes’ stage BDukes’ stages C or DNegative test (%) (n = 20,574)16,698 (81.2)3876 (18.8)530 (2.6)423 (2.1)80 (0.4)27 (0.1)1735Positive test (%) (n = 1231)782 (63.5)449 (36.5)197 (16.0)106 (8.6)39 (3.2)52 (4.2)19718Sensitivity (%) (95% CI)10.4 (9.5–11.3)27.1 (23.9–30.3)20.0 (16.6–23.4)32.7 (24.3–41.2)65.8 (55.4–76.3)52.8 (36.5–69.1)70.0 (41.6–98.4)78.3 (61.4–95.1)Specificity (%) (95% CI)95.5 (95.2–95.8)95.1 (94.8–95.4)94.6 (94.3–94.9)CI, confidence interval.a Except adenomas with high-grade dysplasia. Open table in a new tab CI, confidence interval. A comparison between immunochemical FOBT and colonoscopic findings revealed that neoplasia was detected in 36.5% (449 of 1237) of the FOBT-positive patients and in 18.8% (3876 of 20,574) of the FOBT-negative patients. Patients with positive FOBT had a significantly increased risk for neoplasia compared with those with negative FOBT (relative risk, 1.9; 95% confidence interval, 1.8–2.1). Similarly, patients with positive FOBT were more likely to have advanced neoplasia (relative risk, 6.2; 95% confidence interval, 5.3–7.2) and invasive cancer (relative risk, 32.2; 95% confidence interval, 20.3–51.1) compared with those with negative FOBT. In our population, the positive predictive value decreased with histologic progress of neoplasia (36.5%, 16.0%, and 4.2% for neoplasia, advanced neoplasia, and invasive cancer, respectively). We determined the sensitivity and specificity of immunochemical FOBT according to the location of neoplasia (Table 3). In this analysis, the colon was divided into proximal and distal sections at the splenic flexure. Twenty-four patients had advanced neoplasia both in the proximal and distal colon, and these patients were excluded from this analysis. No patients had invasive cancer in both sections. In patients with advanced neoplasia, neoplasias located at the proximal colon were detected by FOBT at a significantly lower rate (16.3%) compared with neoplasias at the distal colon (30.7%) (P = .00007). Subdividing the results for advanced neoplasia, the difference in the sensitivity according to the location was significant for adenomas 10 mm or greater (P = .0003), but was not significant for adenomas with high-grade dysplasia (P = .82). Moreover, the sensitivity for invasive cancer at the proximal colon was low compared with that at the distal colon, although the difference was significant only in the case of Dukes’ stages C or D (P = .03).Table 3Sensitivity and Specificity of Immunochemical FOBT Stratified According to the Location of NeoplasiaProximal colon (95% CI)Distal colon (95% CI)PSensitivity % Advanced neoplasia16.3 (11.3–21.3)30.7 (26.7–34.8).00007 Adenoma ≥10 mm aExcept adenomas with high-grade dysplasia.11.2 (6.6–15.8)24.5 (20.1–29.1).0003 High-grade dysplasia34.6 (16.3–52.9)32.3 (22.8–41.8).82 Invasive cancer56.5 (36.3–76.8)69.6 (57.6–81.7).26 Dukes’ stage A42.9 (6.2–79.5)55.2 (37.1–73.3).56 Dukes’ stage B50.0 (1.0–99.0)83.3 (53.5–100.0).26 Dukes’ stages C or D55.6 (23.1–88.0)92.9 (79.4–100.0).03Specificity % Advanced neoplasia94.5 (94.2–94.8)95.0 (94.7–95.3) Invasive cancer94.4 (94.1–94.7)94.5 (94.2–94.8)CI, confidence interval.a Except adenomas with high-grade dysplasia. Open table in a new tab CI, confidence interval. We evaluated the sensitivity of Magstream 1000/Hem SP, a type of immunochemical FOBT, in asymptomatic participants who underwent a complete colonoscopy. Many studies have provided information on immunochemical FOBT sensitivity and specificity for the detection of CRC, in which the sensitivity ranged from 47.1% to 100%, and the specificity ranged from 88.2% to 97.1%. 4St John D.J. Young G.P. Alexeyeff M.A. Deacon M.C. Cuthbertson A.M. Macrae F.A. Penfold J.C. Evaluation of new occult blood tests for detection of colorectal neoplasia.Gastroenterology. 1993; 104: 1661-1668PubMed Google Scholar, 5Allison J.E. Tekawa I.S. Ransom L.J. Adrain A.L. A comparison of fecal occult-blood tests for colorectal-cancer screening.N Engl J Med. 1996; 334: 155-159Crossref PubMed Scopus (531) Google Scholar, 19Wong W.M. Lam S.K. Cheung K.L. Tong T.S. Rozen P. Young G.P. Chu K.W. Ho J. Law W.L. Tung H.M. Choi H.K. Lee Y.M. Lai K.C. Hu W.H. Chan C.K. Yuen M.F. Wong B.C. Evaluation of an automated immunochemical fecal occult blood test for colorectal neoplasia detection in a Chinese population.Cancer. 2003; 97: 2420-2424Crossref PubMed Scopus (56) Google Scholar, 20Rozen P. Knaani J. Samuel Z. Performance characteristics and comparison of two immunochemical and two guaiac fecal occult blood screening tests for colorectal neoplasia.Dig Dis Sci. 1997; 42: 2064-2071Crossref PubMed Scopus (47) Google Scholar, 21Nakama H. Kamijo N. Miyata K. Fattah A.A. Zhang B. Uehara Y. Sensitivity and specificity of several immunochemical tests for colorectal cancer.Hepatogastroenterology. 1998; 45: 1579-1582PubMed Google Scholar, 22Nakama H. Zhang B. Fattah A.A. A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer.Eur J Cancer. 2000; 36: 647-650Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, 23Nakama H. Yamamoto M. Kamijo N. Li T. Wei N. Fattah A.A. Zhang B. Colonoscopic evaluation of immunochemical fecal occult blood test for detection of colorectal neoplasia.Hepatogastroenterology. 1999; 46: 228-231PubMed Google Scholar, 24Wong B.C. Wong W.M. Cheung K.L. Tong T.S. Rozen P. Young G.P. Chu K.W. Ho J. Law W.L. Tung H.M. Lai K.C. Hu W.H. Chan C.K. Lam S.K. A sensitive guaiac faecal occult blood test is less useful than an immunochemical test for colorectal cancer screening in a Chinese population.Aliment Pharmacol Ther. 2003; 18: 941-946Crossref PubMed Scopus (69) Google Scholar, 25Greenberg P.D. Bertario L. Gnauck R. Kronborg O. Hardcastle J.D. Epstein M.S. Sadowski D. Sudduth R. Zuckerman G.R. Rockey D.C. A prospective multicenter evaluation of new fecal occult blood tests in patients undergoing colonoscopy.Am J Gastroenterol. 2000; 95: 1331-1338Crossref PubMed Google Scholar In these studies, however, colonoscopy was performed only in FOBT-positive cases, 5Allison J.E. Tekawa I.S. Ransom L.J. Adrain A.L. A comparison of fecal occult-blood tests for colorectal-cancer screening.N Engl J Med. 1996; 334: 155-159Crossref PubMed Scopus (531) Google Scholar, 6Castiglione G. Zappa M. Grazzini G. Mazzotta A. Biagini M. Salvadori P. Ciatto S. Immunochemical vs guaiac faecal occult blood tests in a population-based screening programme for colorectal cancer.Br J Cancer. 1996; 74: 141-144Crossref PubMed Scopus (77) Google Scholar or studies were conducted on a small scale. 19Wong W.M. Lam S.K. Cheung K.L. Tong T.S. Rozen P. Young G.P. Chu K.W. Ho J. Law W.L. Tung H.M. Choi H.K. Lee Y.M. Lai K.C. Hu W.H. Chan C.K. Yuen M.F. Wong B.C. Evaluation of an automated immunochemical fecal occult blood test for colorectal neoplasia detection in a Chinese population.Cancer. 2003; 97: 2420-2424Crossref PubMed Scopus (56) Google Scholar, 21Nakama H. Kamijo N. Miyata K. Fattah A.A. Zhang B. Uehara Y. Sensitivity and specificity of several immunochemical tests for colorectal cancer.Hepatogastroenterology. 1998; 45: 1579-1582PubMed Google Scholar, 22Nakama H. Zhang B. Fattah A.A. A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer.Eur J Cancer. 2000; 36: 647-650Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar, 23Nakama H. Yamamoto M. Kamijo N. Li T. Wei N. Fattah A.A. Zhang B. Colonoscopic evaluation of immunochemical fecal occult blood test for detection of colorectal neoplasia.Hepatogastroenterology. 1999; 46: 228-231PubMed Google Scholar, 25Greenberg P.D. Bertario L. Gnauck R. Kronborg O. Hardcastle J.D. Epstein M.S. Sadowski D. Sudduth R. Zuckerman G.R. Rockey D.C. A prospective multicenter evaluation of new fecal occult blood tests in patients undergoing colonoscopy.Am J Gastroenterol. 2000; 95: 1331-1338Crossref PubMed Google Scholar The most desirable method to assess the diagnostic accuracy of a screening test may comprise both a screening test and a close follow-up examination of all asymptomatic patients in a given community. Because there are few reliable studies that fulfill these criteria, we examined a large asymptomatic population by conducting both immunochemical FOBT and colonoscopy to determine the plausible prevalence of colorectal neoplasia and to evaluate immunochemical FOBT precisely. In our study, we adopted an immunochemical method for conducting FOBT because immunochemical FOBT reportedly has a higher sensitivity at detecting CRC than the guaiac-based occult blood test. 4St John D.J. Young G.P. Alexeyeff M.A. Deacon M.C. Cuthbertson A.M. Macrae F.A. Penfold J.C. Evaluation of new occult blood tests for detection of colorectal neoplasia.Gastroenterology. 1993; 104: 1661-1668PubMed Google Scholar, 5Allison J.E. Tekawa I.S. Ransom L.J. Adrain A.L. A comparison of fecal occult-blood tests for colorectal-cancer screening.N Engl J Med. 1996; 334: 155-159Crossref PubMed Scopus (531) Google Scholar, 6Casti
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