Readability and sensitivity of a new faecal occult blood test in a hospital ward environment. Comparison with an established test

Detection of colorectal cancer in symptomatic outpatients without visible rectal bleeding: Validity of the fecal occult blood test

Background:

In 2002, a new diagnostic strategy in symptomatic outpatients without known established colorectal cancer risk factors aged 40 years or older was implemented in Denmark. Fecal occult blood test (Hemoccult Sensa®) was a part of that strategy in patients without visible rectal bleeding.

Aims:

The aim was to assess the validity of the Hemoccult Sensa® test in detecting colorectal cancer in the above-mentioned outpatients.

Patients:

Symptomatic outpatients without known established colorectal cancer risk factors and without visible rectal bleeding.

Methods:

Hemoccult Sensa® was performed before endoscopic examination. Colorectal cancer was identified at histopathological examination. Patients completed a questionnaire about their symptoms before their first hospital appointment.

Results:

Eight of 256 patients were found to have colorectal cancer. Median patient age was 63 years. The positive predictive value, negative predictive value, sensitivity, and specificity of Hemoccult Sensa® for colorectal cancer were 10.5% (95% confidence interval [CI]: 6.8–14.3), 99.0% (95% CI: 97.8–100.0), 75.0% (95% CI: 69.7–80.3), and 79.4% (95% CI: 74.5–84.4).

Conclusions:

Hemoccult Sensa® as the initial examination in symptomatic outpatients without known established colorectal cancer risk factors presenting without rectal bleeding has to be used with caution. We did not find Hemoccult Sensa® test to be an acceptable alternative to flexible sigmoidoscopy.

Comparison of a brush-sampling fecal immunochemical test for hemoglobin with a sensitive guaiac-based fecal occult blood test in detection of colorectal neoplasia

BACKGROUND

Fecal immunochemical tests (FIT) are an advanced fecal occult blood test (FOBT) technology that reduces barriers to population screening by simplifying the logistics of stool-sampling. The current study was conducted to undertake a paired comparison of a sensitive guaiac FOBT (GFOBT; Hemoccult II Sensa, Beckman Coulter, Fullerton, CA) with a brush-sampling FIT (InSure; Enterix, North Ryde, NSW, Australia), to determine whether this FIT improves detection of significant neoplasia.

METHODS

Individuals sampled consecutive stools, at home, with both FIT and GFOBT sampling devices while following dietary restrictions appropriate for GFOBT. Study populations included a screening cohort (n = 2351) and a symptomatic diagnostic group (n = 161). Paired comparison of positivity rates was undertaken in those found to have cancer and/or significant adenoma (high-grade dysplasia, villous change, > or =10 mm, serrated histology or > or =3 polyps), benign pathology, or no pathology.

RESULTS

Combined results for both cohorts showed that the FIT returned a true-positive result significantly more often in cancer (n = 24; 87.5% vs. 54.2%) and in significant adenomas (n = 61; 42.6% vs. 23.0%). Of all UICC Stage I cancers, the FIT was positive in 12 of 13 compared with 4 of 13 with the GFOBT (P = .002). In analyses of just the screening cohort, the FIT remained significantly better at detecting cancers and significant adenomas; the false-positive rate for any neoplasia was marginally higher with the FIT than the GFOBT (3.4% vs. 2.5%; 95% CI of difference, 0-1.8%), whereas positive predictive values were 41.9% and 40.4%, respectively.

CONCLUSIONS

This brush-sampling FIT is more sensitive for cancers and significant adenomas than a sensitive GFOBT. As such, it should deliver greater reductions in colorectal cancer mortality and incidence than the GFOBT.

Noninvasive testing for colorectal cancer: a review

OBJECTIVES

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Endoscopic screening is now in favor and its use is increasing, but overall participation rates are poor. A substantial percentage of the population will likely continue to resist endoscopic screening. As such, a noninvasive biomarker for the early detection of CRC remains a priority. Herein, we (i) review the currently available noninvasive screening markers for the early detection of CRC, (ii) discuss newer markers that have undergone preliminary testing, and (iii) introduce and explain potentially promising markers of the future.

METHODS

The published literature on markers for early detection of CRC was identified using a MEDLINE/PubMed search with secondary review of cited publications.

RESULTS

Noninvasive testing for CRC is most advanced in testing for stool fecal occult blood, globin, or DNA mutations. Study of abnormal mucins has also been explored. Research for serum-based markers is just beginning and includes serum proteomics, nuclear matrix proteins, and serum DNA testing.

CONCLUSIONS

Serial guaiac-based fecal occult blood testing (FOBT) is simple, inexpensive, and proven effective at reducing mortality from CRC. Immunochemical fecal occult blood tests facilitate compliance and offer improved specificity, but at increased cost in comparison to FOBT. Fecal DNA testing may provide enhanced sensitivity for detection of CRC in comparison with FOBT, but its high cost limits its use for generalized screening. Rectal mucin testing requires additional evaluation to determine its sensitivity and specificity in comparison with guaiac-based FOBT. Serum tests, such as proteomics, nuclear matrix proteins, and serum DNA, are still in their infancy, but remain a hope for the future.

A prospective multicenter evaluation of new fecal occult blood tests in patients undergoing colonoscopy

OBJECTIVE

Guaiac-based fecal occult blood (FOB) tests, in particular, Hemoccult II (HO), are commonly used to detect colorectal neoplasia. Because the sensitivity and specificity of these tests are critical to cost-effective screening programs, we aimed to investigate the improved performance characteristics of new FOB tests for known colonic lesions.

METHODS

Nine centers worldwide performed FOB testing with guaiac-based tests (Hemoccult II [HO] and Hemoccult II SENSA [SENSA]) and immunochemical tests (HemeSelect [HS] and FlexSure OBT [FS]) on 554 patients referred for colonoscopy for predetermined indications. A combination testing strategy consisting of SENSA followed by HS or FS (which was considered positive only when both tests were positive) was also evaluated. Results of FOB tests were compared to findings on colonoscopy.

RESULTS

Cancers were identified in 2.9% of subjects, whereas adenomas > or =10 mm were found in 39 patients. Small adenomas, colitis, and other lesions were identified in 141 patients. The positivity rate of HO for adenomas > or =10 mm was less than for SENSA (20.5% vs 35.9%, p < 0.05), whereas the positivity rate of HO, SENSA, FS, HS, or the combination tests for cancers was not statistically different. The overall positivity rates were significantly greater for FS (15.9%, p = 0.0002) and significantly lower using the combination tests (SENSA/FS 6.0%, p = 0.01; SENSA/HS 6.2%, p = 0.02) compared to HO (9.4%). In this study population, the relative specificity (i.e., true-negative tests/true-negatives + false-positives in patients without adenomas > or =10 mm or cancers) of HO (93.9%; 95% CI, 91.7-96.1) was similar to that of SENSA (92.8%; 95% CI, 90.4-95.2) and HS (90.1%; 95% CI, 87.4-92.8), and greater than FS (88.0%; 95% CI, 85.1-90.9, p < 0.001). When considering adenomas > or =10 mm, cancers alone or cancers and adenomas combined, the combination test using SENSA/FS was associated with significantly fewer false-positive tests than any of the individual tests.

CONCLUSIONS

Compared to single tests, the combination test with the highly sensitive SENSA and an immunochemical test had slightly reduced sensitivity but significantly fewer false-positive tests than any single test. These data raise the possibility that a combination test (i.e., highly sensitive guaiac plus immunochemical) could reduce the costs of screening for colon cancer, and suggest that further study of combination test strategies is warranted.

John DJB, Young GP. Interference of Plant Peroxidases with Guaiac-based Fecal Occult Blood Tests Is Avoidable

Peroxidase-rich fruits and vegetables are reputed to interfere with guaiac-based fecal occult blood tests. We added horseradish peroxidase to fecal samples and tested them with Hemoccult®, Hemoccult SENSA®, and hydrated Hemoccult. Positivity rates with Hemoccult and Hemoccult SENSA decreased rapidly as the time between smearing (preparation) and development increased, whereas they remained high with hydrated Hemoccult. For samples with added blood, positivity rates did not decrease with time. When 61 volunteers were tested on a standard restriction and on a challenge diet high in plant peroxidase, no positive results occurred during standard restriction. During the challenge diet, one volunteer was positive with Hemoccult and Hemoccult SENSA when development was delayed 24 h, and no volunteers were positive when it was delayed 48 h and 72 h. However, with hydrated Hemoccult, positives occurred in 13 of 61 volunteers at 24 h, 8 of 61 at 48 h, and 5 of 61 at 72 h. Thus, peroxidase-rich plant foods do not need to be excluded from the diet with Hemoccult and Hemoccult SENSA if development is delayed for at least 48 h after smearing. A delay of this duration will not solve the problem of plant peroxidase interference with hydrated Hemoccult.

Evaluation of new occult blood tests for detection of colorectal neoplasia

BACKGROUND

Hemoccult II, the guaiac-based fecal occult blood test used in most colorectal cancer screening programs, has an unsatisfactory sensitivity for asymptomatic colorectal neoplasms. We evaluated the relative performance of four fecal occult blood tests, directed against various components of the hemoglobin molecule.

METHODS

All tests, Hemoccult II, HemoccultSENSA (a more sensitive guaiac test), HemeSelect (an immunochemical test specific for human hemoglobin), and HemoQuant (the heme-porphyrin assay), were performed by 107 patients with symptomatic colorectal cancer and 81 patients with predominantly asymptomatic adenoma. Hemoccult-SENSA and HemeSelect were performed by 1,355 screenees.

RESULTS

HemeSelect and Hemoccult-SENSA had significantly higher sensitivity for colorectal cancer (97% and 94%, respectively) than the other tests. HemeSelect had the highest sensitivity for adenomas; in 45 patients with large (> or = 10 mm) adenomas, sensitivity was 76% for HemeSelect, 60% for HemoccultSENSA, and 42% for both Hemoccult and HemoQuant. In the screenees, estimated specificity was 97.8% for HemeSelect and 96.1% for Hemoccult-SENSA.

CONCLUSIONS

HemeSelect and Hemoccult-SENSA have the highest levels of sensitivity for detection of colorectal neoplasia, but the immunochemical test HemeSelect provides the best combination of specificity and sensitivity.