Sensitivity of hemoccult testing in patients with colorectal carcinoma

Hemoccult Sensitivity Estimate in a Screening Program for Colorectal Cancer in the Province of Florence

The sensitivity of Hemoccult testing (HO) in a population-based screening for colorectal cancer was evaluated. HO sensitivity estimates were calculated as the ratio of screen-detected HO-positives to total screen or interval-detected cancers. Sensitivity was estimated according to 1, 2, and 3-year rescreening intervals. Corresponding estimates are 69.4%, 61.8% and 57.7%, respectively. No significant correlation was observed between HO sensitivity and other variables, such as calendar period, tumor stage or site, or patient age or sex. HO sensitivity as estimated in the present experience is consistent with other reports of population-based screenings. Screening every year would achieve too limited an increase in sensitivity, compared to biennal screening, to be worth the difficulties of doubling organizational efforts and costs.

Association between genital intraepithelial lesions and anal squamous intraepithelial lesions in HIV-negative women

OBJECTIVE

The objective of the study was to evaluate the risk of anal squamous intraepithelial lesions (ASILs) in immunocompetent women with genital squamous intraepithelial lesions (GSILs).

STUDY DESIGN

This was a cross-sectional study that included 260 immunocompetent women divided into 2 study groups: 1 group included 184 women diagnosed with GSIL by genital colposcopy and biopsy, and the other included 76 controls. All subjects were submitted to anoscopy followed by a biopsy if pertinent.

RESULTS

Of 184 GSIL women, 32 (17.4%) had ASIL (P<.001). The risk of ASIL was 13.1 times greater for GSIL women when there were 3 or 4 genital sites involved. All cases of high-grade ASIL were found in women with cervical GSILs. Among risk factors, anal intercourse without a condom demonstrated an important association with ASIL (prevalence ratio adjusted for age=2.6).

CONCLUSION

There seems to be a strong association between ASIL and multicentric GSIL. Another factor related to ASIL was the practice of unprotected anal intercourse.

Evaluation of a new test for colorectal neoplasms: a prospective study of asymptomatic population

In a recent pilot study, we have suggested of potential usefulness of a new test (Shams' test) for screening colorectal (CR) cancer in Japan. Although the sensitivity of this test was remarkably high, its accurate specificity was unclear. The purpose of our present study is to evaluate the incidence of non-specific reaction of Shams' test in the normal Japanese populations. We analyzed 330 asymptomatic individuals, who were seen for annual health checkup, for the presence of the tumor marker D-Gal-B (1- > 3)-D-GalNAc in their rectal mucin. The rectal mucin was smeared on nitrocellulose membrane filter and developed by a sequential reaction of B-D-galactose oxidase and Schiff's reagent. Immunological fecal occult blood test (FOBT) was done in parallel. Extensive study by barium enema/total colonoscopy was indicated only for those who showed positive results with Shams' test or FOBT. A total of 271 individuals were negative, while 50 and 9 had positive and equivocal (+/-) results, respectively. Subsequent barium enema and fiberoptic proctocolonoscopic examinations, which were available on 32 of 59 cases, revealed 6 adenomatous polyps, one villous adenoma with focal severe atypia, and 4 cases of diverticular disease. Except for one patient with polyp, 6 other patients harboring polyps were negative with immunological FOBT. The overall specificity of Shams' test was 92.2% (271/294). Based on these results and preceding reports, we concluded that Shams' test could be a useful tool in our strategy for early detection of CR neoplasms and precancerous lesions.

Evaluation of effectiveness of mass screening for colorectal cancer

As the first step in the epidemiological evaluation of the effectiveness of mass screening for colorectal cancer, we compared clinicopathological features and survival rates of patients with cancer detected by mass screening (screened group) with those for patients treated in our outpatient clinic in the same period (outpatient group). The screened group consisted of 53 patients with colorectal cancer detected by 2-day or 3-day screening for fecal occult blood by guaiac slides. Their background factors were comparable to those of 120 patients of the outpatient group in regard to age, sex ratio, location of cancer, and histological type of cancer. In the screened group, 90% of patients had no complaints, and positive occult blood tests led to the detection of cancers. More than 60% of the patients had Dukes' A and B1 early cancers while only about 30% had advanced cancers. In the outpatient group, nearly 90% of patients were symptomatic, most commonly from rectal bleeding. Early-stage cancers made up only 20%, and large, advanced-stage cancers accounted for 80%. The 5-year survival rate of the screened group was 91.5%, being significantly higher than the 60% survival rate for the outpatient group. It is anticipated that mass screening for colorectal cancer by guaiac fecal occult blood testing will significantly reduce the mortality due to this neoplasm.

Inguinal herniation justifies sigmoidoscopy

Controversy exists concerning the association of inguinal hernia and colonic carcinoma and, more specifically, whether the development of an inguinal hernia justifies sigmoidoscopy. To study the role of endoscopic screening in cases of inguinal hernia, we prospectively evaluated 464 patients with inguinal hernia over a 54-month period with flexible sigmoidoscopy. Each patient was over the age of 40 and male. Sigmoidoscopy documented polyps (97 patients, 21 percent) and carcinoma (22 patients, 5 percent). Multiple neoplasms were observed in 6 percent (7 of 119 patients). Occult blood was detected in the fecal specimens of 8 percent of the total group of patients, but in only 13 percent of the patients with polyps or carcinomas. A normal examination occurred in only 38 percent of the total group. By using the presence of an inguinal hernia in patients older than 40 years of age as an indication for sigmoidoscopy, we found that more than one of every four patients had an asymptomatic, concurrent malignant or premalignant colonic lesion. Flexible sigmoidoscopy should be used for screening colonic neoplasms in patients with inguinal hernia.

Colonoscopic detection of early colorectal cancers. Impact of a surgical endoscopy service

The Surgical Endoscopy Service has been aggressively evaluating gastrointestinal symptoms with colonoscopy and screening asymptomatic patients with flexible sigmoidoscopy in hopes of finding early curable colorectal cancers. The purpose of this study was to compare the stages of colorectal cancers resected during the 18-month period prior to (Pre-SES) and during the first 18 months (Post-SES) after the creation of the Surgical Endoscopy Service. In addition, the yield of lesions that would have been obtained by depending upon patient symptoms or occult blood testing were determined. A total of 361 colonoscopies were performed Pre-SES and 874 colonoscopies Post-SES; 26 patients underwent resection of colorectal cancers Pre-SES and 32 Post-SES. Whereas early colorectal cancers (Dukes' A and B1) were found in only three patients (12%) Pre-SES period, early cancers were found in 13 (41%) Post-SES. Doubling the number of colonoscopies produced a fourfold increase in the number of early lesions. Furthermore, disseminated cancers (D lesions) dropped from 19% Pre-SES to 3% Post-SES. Among the total 58 patients, 43% of the A lesions and 40% of the B1 lesions were asymptomatic. Even more alarming, 86% of the A lesions, 50% of the B1 lesions, 31% of the B2 lesions, and 14% of the C2 lesions were occult blood negative. Indeed, only the D lesions were uniformly occult blood positive. This study demonstrates that aggressive colonoscopy detects early colorectal cancers. Moreover, patient symptoms or occult blood testing will fail to indicate the majority of early colorectal cancers.

The relative value of fecal occult blood tests and flexible sigmoidoscopy in screening for large bowel neoplasia

The secondary prevention of colorectal cancer is based on the early detection of noninvasive cancer and removal of adenomatous polyps. The two commonly used screening tests are flexible sigmoidoscopy and guaiac fecal occult blood testing. Both were performed simultaneously and independently on 1176 asymptomatic volunteers followed by colonoscopic examination if either occult blood or a neoplasm was detected. Neoplasia (adenomatous polyps or cancer) were found in 48 screenees. Only ten had positive stool occult blood while 45 were detected by sigmoidoscopy. Analysis of sensitivity for neoplasia was 93.8% for sigmoidoscopy but only 20.8% for the occult blood tests, while the positive predictive values for neoplasia were 100% and 23.8% respectively. The fecal occult blood test detected only 18% of screenees with adenomas and 60% with invasive cancer. Flexible sigmoidoscopy detected 95% and 80% respectively. Analysis (kappa statistic) demonstrated little agreement between the two tests (P greater than 0.05), indicating that they are diagnosing different neoplasia. Evaluation of expected gain in diagnosing neoplasia, by combining both tests, gave 18% for the fecal blood test and 94% for the endoscopic test. These results confirm the complementary value of performing both tests, but especially the high sensitivity and predictive value positive of flexible sigmoidoscopy for adenomas, including those with severe dysplasia, and the converse for the fecal occult blood test. This latter test must be recommended and used within a screening program with caution and full understanding of its limitations.

The pros and cons of fecal occult blood testing for colorectal neoplasms

Testing feces for occult blood is widely recommended as a means of detecting subclinical colorectal tumors. Guaiac tests such as Hemoccult are the most widely used, but chemical sensitivity is relatively low and the tests are affected by dietary peroxidases, the state of fecal hydration, and certain drugs. The newly devised HemoQuant and immunologic techniques appear more sensitive and specific, but they require further evaluation before widespread clinical usage can be recommended. Occult blood screening has both merits and weaknesses. Testing does uncover subclinical colorectal cancer, often at a relatively early stage, but whether this actually improves the prognosis remains to be proven. Benign neoplastic polyps are also detected, although it is debatable whether this is a valid rationale for screening. Test sensitivity for malignancy varies from good to moderate, but is poor for benign polyps. Specificity is usually around 97%-98%, yet the predictive value of a positive test for cancer is only about 10%; hence most test-positive individuals are needlessly subjected to invasive colonic investigations. Reported figures on public compliance with occult blood testing vary widely from excellent to poor. Published costs of screening are usually quite low, but these overlook important indirect and hidden expenses and are therefore misleading. On balance, the problems of occult blood testing currently appear to outweight the merits. This could change, however, with the newer testing techniques and with awaited mortality data from controlled clinical trials now underway.

Screening for colorectal neoplasms. A comparison of the fecal occult blood test and endoscopic examination

Testing for occult blood in stool is used frequently as a screening technique for colorectal carcinomas, but no study has ever shown an improved survival rate for colorectal carcinoma in patients screened by this method. Consequently, the authors have prospectively compared the sensitivity of endoscopy and occult blood testing in finding colorectal neoplasms. During the first year of the Surgical Endoscopy Service, 585 patients underwent sigmoidoscopy or colonoscopy. Seventy-nine patients (13.5 percent) were excluded from the study because their occult blood status was not recorded. Patients averaged 63 + 10 years of age and 98 percent were men. Of the 348 patients with occult blood negative stools 55.5 percent underwent colonoscopy and 44.5 percent underwent sigmoidoscopy. Polyps were found in 25.6 percent of these patients, colorectal carcinomas in 2.6 percent, and diverticulosis 36.2 percent. Of the 158 patients with occult blood positive stool, 76.5 percent underwent colonoscopy and 23.4 percent underwent sigmoidoscopy. Polyps were discovered in 39.0 percent of these patients, colorectal carcinomas in 10.1 percent, and diverticulosis in 43.0 percent. Thus, the occult blood test was negative in 59 percent of patients with polyps and 36 percent with colorectal cancers. These data indicate that lower gastrointestinal endoscopy is superior to occult blood testing in detecting colorectal neoplasms. These results further suggest that using the occult blood test as a screening test for colorectal neoplasms will result in a significant number of these lesions being missed at an early curable stage.

Screening of colorectal cancer

Colorectal cancer (CRC) remains a cancer in a disappointing location. However, its location clearly has an advantage that could theoretically permit efficient secondary prevention: the preceding of the cancer by a benign lesion, ie, the adenoma. Complete colonoscopy and its substitute, the double-contrast barium enema, and their specific limitations, must be reserved for high-risk patients: hereditary cancers and ulcerative colitis. For all the others, ie, adults of 45 years of age and with standard risks, the proposal is either to select the patients to be colonoscoped through occult blood testing of the stools or to perform a fiber sigmoidoscopy or a combination of both. Although imperfect, both methods allow the detection of polyps and cancers at a presymptomatic stage, when they are either benign or malignant, but localized and with a better prognosis. However, the absolute proof of the benefits of this strategy of screening would be the demonstration by controlled studies of a prolonged survival rate or a decrease in morbidity. Until now, this proof is not fully available.