Evaluation of the guaiac fecal occult blood test for detection of gastrointestinal bleeding in the rhesus macaque (Macaca mulatta).

BACKGROUND: Gastrointestinal (GI) hemorrhage accompanies several common diseases of rhesus macaques (Macaca mulatta). Guaiac fecal occult blood testing (gFOBT) is a non-invasive means to detect such bleeding in several species; however, there are currently no data indicating reliability of this test to detect GI hemorrhage in macaques. METHODS: We evaluated sensitivity and specificity of gFOBT to detect simulated and biopsy-associated bleeding in the stomach, duodenum, and colon of 15 rhesus macaques. Fecal samples were analyzed via gFOBT for 72 hours. RESULTS: Guaiac fecal occult blood testing was more sensitive to detect lower vs upper GI bleeding; sensitivity was volume-dependent in the upper GI tract. Single-test specificity was 95.2%. Repeated fecal collections increased gFOBT sensitivity without affecting specificity. CONCLUSIONS: Guaiac fecal occult blood testing is a useful screening test for both upper and lower GI bleeding in rhesus macaques. For highest sensitivity, gFOBT should be performed on three fecal samples collected 24 hours apart.

Increased uptake and improved outcomes of bowel cancer screening with a faecal immunochemical test: results from a pilot study within the national screening programme in England.

BACKGROUND: The National Health Service Bowel Cancer Screening Programme (BCSP) in England uses a guaiac-based faecal occult blood test (gFOBt). A quantitative faecal immunochemical test (FIT) for haemoglobin (Hb) has many advantages, including being specific for human blood, detecting Hb at a much lower concentration with a single faecal sample and improved uptake. METHODS: In 2014, a large comparative pilot study was performed within BCSP to establish the acceptability and diagnostic performance of FIT. Over a 6-month period, 40 930 (1 in 28) subjects were sent a FIT (OC-SENSOR) instead of a gFOBt. A bespoke FIT package was used to mail FIT sampling devices to and from FIT subjects. All participants positive with either gFOBt or FIT (cut-off 20 µg Hb/g faeces) were referred for follow-up. Subgroup analysis included cut-off concentrations, age, sex, screening history and deprivation quintile. RESULTS: While overall uptake increased by over 7 percentage points with FIT (66.4% vs 59.3%, OR 1.35, 95% CI 1.33 to 1.38), uptake by previous non-responders almost doubled (FIT 23.9% vs gFOBt 12.5%, OR 2.20, 95% CI 2.10 to 2.29). The increase in overall uptake was significantly higher in men than women and was observed across all deprivation quintiles. With the conventional 20 µg/g cut-off, FIT positivity was 7.8% and ranged from 5.7% in 59-64-year-old women to 11.1% in 70-75-year-old men. Cancer detection increased twofold and that for advanced adenomas nearly fivefold. Detection rates remained higher with FIT for advanced adenomas, even at 180 µg Hb/g. CONCLUSIONS: Markedly improved participation rates were achieved in a mature gFOBt-based national screening programme and disparities between men and women were reduced. High positivity rates, particularly in men and previous non-respondents, challenge the available colonoscopy resource, but improvements in neoplasia detection are still achievable within this limited resource.

The immunochemical faecal occult blood test leads to higher compliance than the guaiac for colorectal cancer screening programmes: a cluster randomized controlled trial.

INTRODUCTION: We conducted a cluster-randomized trial aimed at assessing the effect of the type of faecal occult blood, guaiac or immunochemical test on screening compliance. METHODS: We sampled 130 general practitioners (GPs) who consented to participate in the trial. We randomly allocated half of them to the guaiac (Hemo-Fec) and half to the immunochemical test (OC-Hemodia). We sampled 2/10 of the GPs' 50-75-year-old patients (n=7332) and randomly divided this population into half. One half was invited to be screened at the GP's office and the other to the nearest gastroenterology ward. The principal outcome was the percentage of returned tests. RESULTS: The immunochemical test had a compliance of 35.8% and the guaiac of 30.4% (relative risk [RR] 1.20; 95% confidence interval [CI] 1.02-1.44). The difference was mostly due to a higher probability of returning the sample: 93.8% and 88.6% for immunochemical and guaiac, respectively (RR 1.06; 95% CI 1.02-1.10). The guaiac test had a higher prevalence of positives (10.3% versus 6.3%, RR 0.603; 95% CI 0.433-0.837). There was a higher variability in the results obtained with the guaiac test compared with the immunochemical (F[1, 12] = 16.25; P=0.0017). CONCLUSIONS: Compliance is more likely with the immunochemical than the guaiac test, independent of the provider. Guaiac tests show a higher variability of the results among centres. The successful implementation of a screening programme requires a period of standardization of the test reading in order to avoid unexpected work overload for colonoscopy services.

Green-coloured results on guaiac-based faecal occult blood testing should be considered positive.

BACKGROUND: In guaiac-based faecal occult blood tests (FOBT), blue colours are considered positive. Blue-green colours should also be considered positive. Distinct green colours are said to be due to bile and it is stated that these should be interpreted as negative. The purpose of this study was to determine the clinical outcomes in individuals in whom the FOBT had difficult-to-interpret green colours that did not wash out on addition of developer. METHODS: During the examination of 134 844 FOBT received in the Scottish laboratory in the first screening round of the UK Colorectal Cancer Screening Pilot, samples with green colour that did not wash out during development were identified. The clinical outcomes were determined from the comprehensive data set collected for each participant. RESULTS: A small number (77) of FOBT were recorded as green-coloured on development. These were reported as positive and the usual investigation algorithm followed. Significant pathology was present in 31 of the 77 participants (40.3%). Negative outcomes encompassed 39 of the 77 participants (50.6%). The outcome could not be determined accurately for seven of the 77 participants (9.1%). Importantly, 17 of the participants (22.1%) had polyps. CONCLUSIONS: Any green colour that does not wash out to the periphery of the guaiac tape on development of FOBT should be reported as a positive result, and manufacturers should clarify their instructions on interpretation.

Effects of subsequent antioxidant treatment on 7,12-dimethylbenz[a]anthracene-initiated carcinogenesis of the mammary gland, ear duct and forestomach in Sprague-Dawley rats.

The effects of the antioxidants tetramethyl-p-phenylenediamine (TMPD), propyl gallate (PG), quercetin (QC), 2-tert-butyl-4-methylphenol (TBMP), tert-butylhydroquinone (TBHQ), 3,3'-thiodipropionic acid (TDPA), guaiac gum (GG) and caffeic acid (CA) on 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mammary gland, ear duct and forestomach carcinogenesis were examined in female Sprague--Dawley rats. Fifty-day-old rats were treated with 2.5 mg/100 g body wt of DMBA and, commencing 1 week thereafter, were given diets supplemented with 0.1% TMPD, 1.0% PG, 1.0% QC, 1% TBMP, 0.8% TBHQ, 1.0% TDPA, 1.0% GG or 0.5% CA for 51 weeks and then killed. Mammary tumor development was reduced by diet containing TMPD, PG, TBMP, TBHQ or GG, although this could be partly due to antioxidant treatment-associated decrease in body wt gain. The incidence of ear duct tumors was not affected by any of the antioxidant treatments. Development of forestomach tumors was enhanced in the group given DMBA followed by CA.