Effect of season and ambient temperature on outcome of guaiac-based faecal occult blood tests performed for colorectal cancer screening

The guaiac-based fecal occult blood test in healthy dogs: Evaluation of the effects of diet, and the ability of the test to detect fecal occult blood

BACKGROUND

The guaiac-based fecal occult blood test (gFOBt) has been used for human colorectal cancer screening. It can detect the fecal occult blood (FOB) in dogs after oral administration of 20 mg of hemoglobin/kg body weight of blood and is influenced by diet.

OBJECTIVES

The aims were to evaluate the effect of diet and the ability of gFOBt to detect FOB in healthy dogs after oral administration of autologous blood.

METHODS

Five healthy dogs were fed Purina Hypoallergenic (HA) and Gastrointestinal (EN) diets. Feces were tested with gFOBt before starting diets and at each defecation (hereafter referred to as fecal collection event) throughout the study period. Every 4 days, increased doses of autologous blood were administered orally. The whole blood of one dog was progressively diluted with a saline solution, and dilutions were directly tested with the gFOBt, until a negative result was found.

RESULTS

Twelve of 185 (6.5%) gFOBt were found to be positive. No associations between diet and gFOBt positivity were found. A significant association was found between the fecal collection event and gFOBt positivity (P < .001) and between doses of blood and gFOBt positivity (P = .048). The lowest dilution ensuring all positive tests was 6.5 µg_Hgb /mL.

CONCLUSIONS

The gFOBt was not influenced by either the HA or EN diets. The gFOBt positivity was associated with the dose of blood and the fecal collection event. However, caution is needed in the interpretation of results due to the lack of an association between gFOBt positivity and increasing doses of blood in the same dog.

Impact of a new sampling buffer on faecal haemoglobin stability in a colorectal cancer screening programme by the faecal immunochemical test

Haemoglobin (Hb) stability in faecal samples is an important issue in colorectal cancer screening by the faecal immunochemical test (FIT) for Hb. This study evaluated the performance of the FIT-Hb (OC-Sensor Eiken) used in the Florence screening programme by comparing two different formulations of the buffer, both in an analytical and in a clinical setting. In the laboratory simulation, six faecal pools (three in each buffer type) were stored at different temperatures and analysed eight times in 10 replicates over 21 days. In the clinical setting, 7695 screenees returned two samples, using both the old and the new specimen collection device (SCD). In the laboratory simulation, 5 days from sample preparation with the buffer of the old SCD, the Hb concentration decreased by 40% at room temperature (25°C, range 22-28°C) and up to 60% at outside temperature (29°C, range 16-39°C), whereas with the new one, Hb concentration decreased by 10%. In the clinical setting, a higher mean Hb concentration with the new SCD compared with the old one was found (6.3 vs. 5.0 µg Hb/g faeces, respectively, P<0.001); no statistically significant difference was found in the probability of having a positive result in the two SCDs. Better Hb stability was observed with the new buffer under laboratory conditions, but no difference was found in the clinical performance. In our study, only marginal advantages arise from the new buffer. Improvements in sample stability represent a significant target in the screening setting.

Free Fecal Immunochemical Test Disbursement in Eight Family Physician Offices

Colorectal cancer (CRC) is the second leading cause of cancer death. CRC screening with a fecal immunochemical test (FIT) is important as occult blood may be detected. To offer Iowa Research Network members in family physician offices the opportunity to provide FITs at no charge to patients in need and determine how many of the tests would be handed out to patients and how many would be returned to the office. Eight family physician offices agreed to participate and 50 two-day FITs were provided, potentially providing 400 patients a CRC screening test. One hundred and eighty (45%) of the 400 FITs were handed out to patients. Of the 92 (51%) patients who returned at least one card, 77 (84%) had negative results, 13 (14%) were positive, and 2 (2 %) were indeterminate. Of 13 patients with a positive result, 11 (85%) had a follow-up colonoscopy. Providing 400 FITs at no charge to the offices was an expensive endeavor. Implementing this forced a change in office routine and the type of fecal occult blood test used. Less than half of the FITs were given out to patients and of those given out, about half of the patients returned a FIT. For those who returned FITs and had positive findings, 85% followed-up with a colonoscopy. Office nurses implementing the CRC screening need to be included in the planning of the type of fecal occult blood test used and receptive to the project.

Effect of Ambient Temperature Variations on Positivity of Manual Fecal Immunochemical Tests

INTRODUCTION

In the United States, many fecal occult blood tests are mailed by patients to a laboratory for analysis. Hemoglobin is not stable in feces and can be affected by the heat. Effects of season and ambient temperature on fecal immunochemical tests (FITs) have demonstrated a decrease in positivity rates during the hottest season.

OBJECTIVE

To investigate the potential effect of the average of 4-day ambient maximum temperature variations on the positivity of a single sample, one-time Clinical Laboratory Improvement Amendments (CLIA)-waived FIT.

SETTING

Midwestern tertiary care hospital.

METHODS

Individuals scheduled for a colonoscopy were invited to complete a qualitative FIT prior to their colonoscopy in 2010 and 2011. FITs were read as positive or negative.

RESULTS

Valid FITs were received from 1026 individuals over 25 months. The positivity rate was 10.9%. The mean 4-day average of daily maximum ambient temperatures was calculated including the day of receipt for each sample. Fahrenheit temperatures ranged from 16.0 to 96.8. Based on the odds ratio of 1.04 with a confidence interval of 0.94 to 1.14 for a 10°F increase in temperature, there was no statistically significant evidence of an effect of the preceding maximum average 4-day ambient temperature on FIT positivity.

CONCLUSION

No evidence was found that ambient temperature had an effect on positivity rate over a 25-month period using 4 different qualitative FIT products. Further analysis on effect of ambient temperatures is warranted for the automated FITs and CLIA-waived FITs, including liquid-vial and dry-slide FITs. Primary care providers need to be aware of potential adverse effects of FITs.

Faecal occult blood testing for colorectal cancer screening: the past or the future

Screening for colorectal cancer (CRC) reduces CRC mortality; many countries have implemented population-based CRC screening programmes and many more are poised to do so. Whilst several different CRC screening modalities are available, choice will be influenced by cost, available resources (e.g. high-quality colonoscopy) and acceptability of the test by the invited population. For CRC screening, no screening test has so far surpassed the practicality, affordability and effectiveness of tests for the presence of blood in faeces (faecal occult blood tests, FOBt). The results of several large FOBt-based randomised controlled trials provide the best clinical evidence to support their use in population-based CRC screening. This review considers the current options for CRC screening and the future for FOBt.

Advances in Fecal Occult Blood Tests: the FIT revolution

There is a wide choice of fecal occult blood tests (FOBTs) for colorectal cancer screening.

GOAL

To highlight the issues applicable when choosing a FOBT, in particular which FOBT is best suited to the range of screening scenarios. Four scenarios characterize the constraints and expectations of screening programs: (1) limited colonoscopy resource with a need to constrain test positivity rate; (2) a priority for maximum colorectal neoplasia detection with little need to constrain colonoscopy workload; (3) an "adequate" endoscopy resource that allows balancing the benefits of detection with the burden of service provision; and (4) a need to maximize participation in screening. Guaiac-based FOBTs (gFOBTs) have significant deficiencies, and fecal immunochemical tests (FITs) for hemoglobin have emerged as better tests. gFOBTs are not sensitive to small bleeds, specificity can be affected by diet or drugs, participant acceptance can be low, laboratory quality control opportunities are limited, and they have a fixed hemoglobin concentration cutoff determining positivity. FITs are analytically more specific, capable of quantitation and hence provide flexibility to adjust cutoff concentration for positivity and the balance between sensitivity and specificity. FITs are clinically more sensitive for cancers and advanced adenomas, and because they are easier to use, acceptance rates are high.

CONCLUSIONS

FOBT must be chosen carefully to meet the needs of the applicable screening scenario. Quantitative FIT can be adjusted to suit Scenarios 1, 2 and 3, and for each, they are the test of choice. FITs are superior to gFOBT for Scenario 4 and gFOBT is only suitable for Scenario 1.

Tests and investigations for colorectal cancer screening

Worldwide, colorectal (CRC) is the third most common form of cancer, after lung and breast cancer, and the fourth most common cause of cancer death, although in developed countries CRC incidence is higher and it accounts for an even higher proportion of cancer deaths. Successful treatment of early-stage CRC confers substantial survival advantage, and there is now overwhelming evidence that screening average-risk individuals for CRC reduces the incidence and disease-specific mortality. In spite of considerable research for new biomarkers for CRC, the detection of blood in faeces remains the most effective screening tool. The best evidence to date for population-based CRC screening comes from randomised-controlled trials that used a guaiac-based faecal occult blood test (gFOBt) as the first-line screening modality, whereby test-positive individuals are referred for follow-up investigations, usually colonoscopy. A major innovation in the last ten years or so has been the development of other more analytically sensitive and specific screening techniques for blood in faeces. The faecal immunochemical test for haemoglobin (FIT) confers substantial benefits over gFOBt in terms of analytical sensitivity, specificity and practicality and FIT are now recommended for CRC screening by the European guidelines for quality assurance in colorectal cancer screening and diagnosis. The challenge internationally is to develop high quality CRC screening programmes for which uptake is high. This is especially important for developing countries witnessing an increase in the incidence of CRC as populations adopt more westernised lifestyles. This review describes the tests available for CRC screening and how they are being used worldwide. The reader will gain an understanding of developments in CRC screening and issues that arise in choosing the most appropriate screening test (or tests) for organised population-based screening internationally and optimising the performance of the chosen test (or tests). Whilst a wide range of literature has been cited, this is not a systematic review. The authors provide FOBT CRC screening for a population of 14.6 million in the south of England and the senior author (SPH) was the lead author of the European guidelines for quality assurance in colorectal cancer screening and diagnosis and leads the World Endoscopy Organization Colorectal Cancer Committee's Expert Working Group on 'FIT for Screening'.