Performance characteristics and evaluation of an automated-developed and quantitative, immunochemical, fecal occult blood screening test

Population-based colorectal cancer screening: comparison of two fecal occult blood test

BACKGROUND

The aim of screening for colorectal cancer is to improve prognosis by the detection of cancer at its early stages. In order to inform the decision on the specific test to be used in the population-based program in the Basque Autonomous Region (Spain), we compared two immunochemical fecal occult blood quantitative tests (I-FOBT).

METHODS

Residents of selected study areas, aged 50-69 years, were invited to participate in the screening. Two tests based on latex agglutination (OC-Sensor and FOB Gold) were randomly assigned to different study areas. A colonoscopy was offered to patients with a positive test result. The cut-off point used to classify a result as positive, according to manufacturer's recommendations, was 100 ng/ml for both tests.

RESULTS

The invited population included 37,999 individuals. Participation rates were 61.8% (n = 11,162) for OC-Sensor and 59.1% (n = 11,786) for FOB Gold (p = 0.008). Positive rate for OC-Sensor was 6.6% (n = 737) and 8.5% (n = 1,002) for FOB Gold (p < 0.0001). Error rates were higher for FOB gold (2.3%) than for OC-Sensor (0.2%; p < 0.0001). Predictive positive value (PPV) for total malignant and premalignant lesions was 62.4% for OC-Sensor and 58.9% for FOB Gold (p = 0.137), respectively.

CONCLUSION

OC-Sensor test appears to be superior for I-FOBT-based colorectal cancer screening, given its acceptance, ease of use, associated small number of errors and its screening accuracy. FOB Gold on the other hand, has higher rate of positive values, with more colonoscopies performed, it shows higher detection incidence rates, but involves more false positives.

Opportunistic screening for colorectal neoplasia in Singapore using faecal immunochemical occult blood test

INTRODUCTION

The use of faecal immunochemical occult blood test (FIT) has been reported to decrease mortality from colorectal cancer. The Singapore Cancer Society (SCS) gives out FIT kits to encourage opportunistic screening of colorectal cancer. Any Singapore citizen or permanent resident aged ≥ 50 years is eligible to receive two FIT kits. Participants with at least one positive FIT are referred for further evaluation. We aimed to analyse the results of SCS data from the year 2008.

METHODS

The factors evaluated included compliance, positive test rate (PR) and positive predictive value (PPV) of FIT.

RESULTS

20,989 participants received 41,978 kits in 2008. Compliance was 38.9%, with 8,156 participants returning at least one kit. 8% of participants tested positive, and 75% of these test-positive participants agreed to undergo further investigations. 33 participants had colorectal cancers, 45 had advanced polyps (≥ 1 cm) and 90 had polyps < 1 cm. Histologically, 114 polyps were adenomatous, 20 were hyperplastic and 1 was serrated. PPV of colorectal neoplasia for those who underwent further colonoscopy was 34%. Over half of the participants who had only one positive test had colorectal neoplasia.

CONCLUSION

PR and PPV of FIT in our study were comparable to that in the literature. However, compliance was low and a quarter of all participants who tested positive refused further investigations. Extensive population education programmes are required to improve compliance and tackle inhibitions among the masses. It is also important to take steps to enhance the cost effectiveness of future screening programmes.

Fecal immunochemical test accuracy in familial risk colorectal cancer screening

There is little information on fecal immunochemical test (FIT) in familial risk colorectal cancer (CRC) screening. Our study assesses FIT accuracy, number needed to scope (NNS) and cost to detect a CRC and an advanced neoplasia (AN) in this setting. We performed a multicentric, prospective, double-blind study of diagnostic tests on individuals with first-degree relatives (FDRs) with CRC submitted to screening colonoscopy. Two stool samples were collected and fecal hemoglobin in the first sample (FIT1) and the highest in both samples (FITmax) were determined. Areas under the curve (AUC) for CRC and AN as well as the best FIT1 and FITmax cutoff value for CRC were determined. At this threshold, NNS and the cost per lesion detected were calculated. A total of 595 individuals were included (one FDR > 60 years, 413; two FDR or one ≤ 60 years, 182). AN and CRC were found in 64 (10.8%) and six (1%) patients, respectively. For CRC diagnosis, FIT1 AUC was 0.96 [95% confidence interval (CI): 0.95-0.98] and FITmax AUC was 0.95 (95% CI: 0.93-0.97). For AN diagnosis, FIT1 and FITmax AUC were 0.74 (95% CI: 0.66-0.82). The best cutoff point for CRC was 115. At this threshold, the NNS to detect a CRC was 5.67 and 7.67, and the cost per CRC was 1,064€ and 1591.33€ on FIT1 and FITmax strategies, respectively. FIT shows high accuracy to detect CRC in familial CRC screening. Performing two tests does not improve diagnostic accuracy, but increases cost and NNS to detect a lesion.

Comparison of the performance of guaiac-based and two immunochemical fecal occult blood tests for identifying advanced colorectal neoplasia in Taiwan

OBJECTIVES

We aimed to evaluate the performance of fecal occult blood tests (FOBT) for the screening of colorectal cancer (CRC).

METHODS

We selected participants from a medical center in Taiwan, China from November 2009 to June 2011. All participants underwent screening colonoscopy and were asked to provide their stool samples for qualitative immunochemical FOBT (qlFIT), quantitative immunochemical FOBT (qnFIT) and the guaiac-based FOBT(GT). The receiver operating characteristic curve was utilized to determine the optimal cut-off value of qnFIT. We measured the detection ability of the FOBT for colonic polypoid lesions.

RESULTS

In all, 699 participants were enrolled in this study. For qnFIT, we found increased levels of fecal hemoglobin in participants with polyps ≥10 mm (251.0 ng/mL), villous-containing adenomas (98.7 ng/mL) and advanced adenomas (187.9 ng/mL). The optimal cut-off value for qnFIT was 25 ng/mL for detecting advanced colorectal neoplasms (ACRN). All three FOBT had a similar but low estimate in detecting small and tubular adenomatous polyps. The qnFIT had a better detection ability for large adenomas (positive likelihood ratio [PLR], 5.6 vs 3.1 vs 0.3) and adenomas with villous-components (PLR 3.7 vs 3.3 vs 0.3) than qlFIT and GT. For the ACRN group, qnFIT also showed the best screening ability with a sensitivity of 56.8%, accuracy of 86.7% and PLR 5.0.

CONCLUSIONS

Both qnFIT and qlFIT perform better than GT in detecting advanced adenomas and CRC in the Taiwanese population.

Effect of aspirin and antiplatelet drugs on the outcome of the fecal immunochemical test

OBJECTIVE

To evaluate the effect of aspirin and nonaspirin antiplatelet agents (NAAAs) on the performance of the fecal immunochemical test (FIT).

PARTICIPANTS AND METHODS

We performed a post hoc analysis of results from a clinical trial that involved 28,696 asymptomatic average-risk men and women aged 50 to 69 years invited to participate in a colorectal cancer screening program with FIT between November 1, 2008, and June 31, 2011.

RESULTS

The test was returned by 6390 individuals (22.3%), of whom 5821 (91.1%) reported not using antiplatelet drugs (nonusers group) and 569 (8.9%) reported using these drugs at the time of testing (users group). The FIT result was positive in 48 of 569 users (8.4%) and 365 of 5821 nonusers (6.3%) (P=.05). A positive FIT result was found in 7.3% (28/384) of aspirin users, 7.1% (10/140) of NAAA users, and 22.2% (10/45) of those undergoing dual antiplatelet therapy (DAPT) (aspirin plus an NAAA). The DAPT subgroup had a significantly higher positive FIT rate than the nonuser group (odds ratio, 3.5; 95% CI, 1.7-7.3; P<.05). The positive predictive value (PPV) for advanced neoplasia (AN) in nonusers was 50.4% vs 50.0% in users (P = .40). The PPV for AN was 57.0% in aspirin users, 30.0% in NAAA users, and 50.0% in DAPT users, without statistically significant differences between the user and nonuser groups.

CONCLUSION

The use of DAPT increased the rate of positive FIT results. Use of aspirin, NAAAs, or both did not modify the PPV for AN in this population-based colorectal screening program.

Application of the fecal microRNA test to the residuum from the fecal occult blood test

OBJECTIVE

Though the fecal occult blood test is used for colorectal cancer screening worldwide, it does not have a particularly high sensitivity for detecting colorectal cancer. Here we investigated the applicability of the fecal microRNA test to fecal samples that had been used for a previous fecal occult blood test and stored under various conditions.

METHODS

Five colorectal cancer patients and five healthy volunteers were enrolled. Fecal samples were stored for 0-5 days at 4°C, room temperature or 37°C. Total RNA was extracted from the fecal occult blood test residuum and microRNA expression was analyzed by real-time reverse transcription polymerase chain reaction.

RESULTS

There were no remarkable differences either in colorectal cancer patients or in controls with regard to the concentration of RNA extracted from the fecal occult blood test residuum in any of the storage groups compared with the samples prepared on day 0 (Group 0). Ribosomal RNA stored at room temperature or 37°C degraded rapidly. In contrast, the ribosomal RNA stored at 4°C remained intact for at least 5 days. The microRNAs in samples stored at 4°C and room temperature were conserved; however, the microRNAs stored at 37°C were significantly degraded compared with Group 0 (P < 0.05). In the residuum stored at 4°C up to 5 days, the relative quantification of miR-106a normalized with miR-24 in colorectal cancer patients was significantly higher than those in healthy volunteers (P < 0.05). In contrast, the quantification of normalized miR-106a was remarkably low in samples stored at room temperature and 37°C.

CONCLUSIONS

Fecal microRNA of sufficient quality for reverse transcription polymerase chain reaction analysis was extracted from the fecal occult blood test residuum stored at 4°C for up to 5 days.

Evaluation of fecal immunochemical tests for colorectal cancer screening

BACKGROUND

Colorectal cancer (CRC) screening reduces the mortality due to CRC. It is important for health care providers to be aware of the variation in the products available for CRC screening.

PURPOSE

The purpose of this study was to summarize the accuracy of results of individual fecal immunochemical test (FIT) products across pathology proficiency testing programs.

METHODS

Secondary data analysis of proficiency testing programs' FIT results.

RESULTS

Four of 7 proficiency testing program's FIT evaluations were obtained for a 2-year period. Fourteen unique FIT brands were evaluated by at least 1 of the 4 proficiency testing programs. Five of the products performed similarly with sensitivities ranging from 98.1% to 98.8% and specificities from 98.1% to 99.6%. Ninety-three percent of the FIT tests completed were manual Clinical Laboratory Improvement Amendments-waived FITs.

CONCLUSIONS

About two thirds of the commonly used FIT products performed acceptably on spiked samples of human hemoglobin. However, some had low sensitivity and specificity and probably should not be used for population-based or other screening. Further investigation to determine appropriate, reliable products for fecal occult blood testing is warranted.

Colorectal cancer screening--optimizing current strategies and new directions

The first evidence that screening for colorectal cancer (CRC) could effectively reduce mortality dates back 20 years. However, actual population screening has, in many countries, halted at the level of individual testing and discussions on differences between screening tests. With a wealth of new evidence from various community-based studies looking at test uptake, screening-programme organization and the importance of quality assurance, population screening for CRC is now moving into a new realm, promising better results in terms of reducing CRC-specific morbidity and mortality. Such a shift in the paradigm requires a change from opportunistic, individual testing towards organized population screening with comprehensive monitoring and full-programme quality assurance. To achieve this, a combination of factors--including test characteristics, uptake, screenee autonomy, costs and capacity--must be considered. Thus, evidence from randomized trials comparing different tests must be supplemented by studies of acceptance and uptake to obtain the full picture of the effectiveness (in terms of morbidity, mortality and cost) the different strategies have. In this Review, we discuss a range of screening modalities and describe the factors to be considered to achieve a truly effective population CRC screening programme.

Evaluation of mucosal healing of ulcerative colitis by a quantitative fecal immunochemical test

OBJECTIVES

Accumulating evidence has underlined the importance of mucosal healing as a treatment goal for ulcerative colitis (UC). Quantitative fecal immunochemical tests (FITs), which can rapidly quantify fecal blood with automated equipment, have been used recently to screen for colorectal neoplasia. The aim of this study is to determine whether an FIT can evaluate mucosal healing in UC.

METHODS

Feces collected from UC patients who underwent colonoscopy were examined by FITs, and results were compared with colonoscopic findings. Mucosal status was assessed using the Mayo endoscopic subscore classification. Maximum score for the colorectum in each patient was recorded.

RESULTS

Evaluated were FIT results in conjunction with 310 colonoscopies that were performed in 152 UC patients. A large majority of patients with a Mayo 0 endoscopic score had negative FIT (<100 ng/ml) results (92%), and the proportion of negative FIT results decreased with increases in the Mayo score (Mayo 1: 47%, Mayo 2: 13%, Mayo 3: 12%, P<0.0001, Cochran-Armitage trend test). When the negative FIT was defined as <100 ng/ml, the sensitivity and specificity of a negative FIT for mucosal healing (Mayo 0) were 0.92 and 0.71, respectively. When mucosal healing was defined as Mayo 0 or 1, those were 0.60 and 0.87, respectively. In addition, a positive FIT (≥100 ng/ml) predicted mucosal inflammation (Mayo 2 or 3) with sensitivity 0.87 and specificity 0.60, respectively.

CONCLUSIONS

The FIT can effectively and noninvasively evaluate mucosal healing in UC. This easy, rapid method can help evaluate and control disease activity of UC.

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

AIM

Guaiac-based faecal occult blood tests (gFOBTs) are used in the colorectal cancer screening programme. Recent data suggested that the immunological faecal occult blood test illustrated a variation in positivity according to season and ambient temperature. Our aim was to assess the effect of season and ambient temperature on the positivity rates of the gFOBT during pilot screening for colorectal cancer.

METHOD

Data from the first year of round 1 of the pilot screening programme in Coventry and Warwickshire were analysed. Patients with positive and negative gFOBT samples were included. Patients with spoilt samples or incomplete data were excluded. Of the total of 59513 patients, 30311 were men and 29202 women. Mean age was 56 years. Daily temperature data were provided by the meteorological office.

RESULTS

Median exposure of the gFOBT test card was 6 days (range 1-17). Median daily maximum temperature was 14°C. Spring and summer illustrated significantly decreased positivity rates compared with autumn and winter (Pearson's chi-squared test, P<0.001). Mean daily maximum temperature for the test card exposure showed no significant difference in positivity rates (P=0.53). Subgroup analysis revealed a significant reduction in positive samples in the >25°C subgroup (P=0.045).

CONCLUSIONS

There is a seasonal variation in positivity rates of gFOBTs with increased positivity in spring and summer months. There is no difference in positivity rates in relation to ambient temperature except in subgroup analysis where there is a significant reduction in positivity rates above 25°C.

Performance of the fecal immunochemical test is not decreased by high ambient temperature in the rapid return system

BACKGROUND

Hemoglobin concentration of fecal immunochemical test may be decreased at high ambient temperature, and fecal samples in FIT may be exposed to high ambient temperature.

AIMS

The aim of this study was to determine whether a high ambient temperature on the day of screening may decrease the performance of FITs in population-based screening.

METHODS

We performed FITs for asymptomatic participants aged 50 years or older. Fecal hemoglobin concentration, the probability of a positive FIT and a detection rate of colorectal neoplasms were compared between low (<10.0 °C) and high (≥25.0 °C) temperature groups.

RESULTS

The FIT results for 8,316 participants were analyzed. The mean log(10) Hb concentration in the low temperature group was significantly higher than those in the high temperature group (0.36 vs. 0.25 ng/ml, p = 0.000). Regression analysis showed that an increase in temperature of 1 °C reduced the probability of a positive FIT by 3.1 %. However, we found no differences between the two groups in the FIT positive rate and detection rate of colorectal neoplasms. In multivariate analysis, high ambient temperature was not a significant risk factor for either the positive FIT result or the detection of colorectal neoplasms.

CONCLUSIONS

Potential instability of fecal hemoglobin at high ambient temperatures should be considered; however, its influence on performance of FIT may be attenuated by the short exposure time of fecal samples to high ambient temperature (i.e., rapid return system).

Positivity rates and performances of immunochemical faecal occult blood tests at different cut-off levels within a colorectal cancer screening programme

BACKGROUND

Immunochemical faecal occult blood tests have greater sensitivity for colorectal cancer screening than guaiac-based tests; however the number of positive tests required is still under discussion.

METHODS

A direct comparison of Hemoccult II with two immunochemical quantitative tests (OC-Sensor and FOB-Gold) using a 2-sample strategy was performed in over 30,000 patients undergoing colorectal cancer screening in France.

RESULTS

Positivity ratio between immunochemical tests and Hemoccult II varied between 2.2 (OC-Sensor) and 2.4 (FOB-Gold) for the lowest cut-off value and 1.5-1.4 for the highest cut-off value. The positive predictive value for colorectal cancer was similar for immunochemical tests and Hemoccult II, and significantly higher for immunochemical tests for advanced adenomas. The detection rate of both colorectal cancer and advanced adenomas was higher with immunochemical tests than with Hemoccult II. With the 2-sample strategy and the lowest cut-off value the detection rate of colorectal cancer almost doubled and for advanced adenomas quadrupled.

CONCLUSION

For colorectal cancer screening with immunochemical faecal occult blood tests, an acceptable strategy would be 2-day sampling with at least one positive test at a cut-off between 150 and 200 ng/mL (OC-Sensor) and 176 and 234 ng/mL (FOB-Gold). Data on the ease of test interpretation and cost-effectiveness now necessary to make definitive choices.

Comparison between a guaiac and three immunochemical faecal occult blood tests in screening for colorectal cancer

BACKGROUND

The aim of this study was to compare the performance of the guaiac-based faecal occult blood test (G-FOBT), with that of three immunochemical faecal occult blood tests (I-FOBT) which allow automatic interpretation.

PATIENTS AND METHODS

Under the French organised screening programme, 85,149 average-risk individuals aged 50-74 participating in the third screening round, performed both the G-FOBT (Hemoccult-II test) and one of the I-FOBTs: FOB-Gold, Magstream and OC-Sensor.

RESULTS

Given the chosen threshold, the positivity ratio between the different I-FOBTs and the G-FOBT was 2.4 for FOB-Gold, 2.0 for Magstream and 2.2 for OC-Sensor (P=0.17). The three I-FOBTs were superior to the G-FOBT for colorectal cancer (CRC) detection. The ratios for detection rates were 1.6 (FOB-Gold), 1.7 (Magstream) and 2.1 (OC-Sensor) (P=0.74). For non-invasive CRC they were, respectively, 2.5, 3.0 and 4.0 (P=0.83) and for advanced adenomas 3.6, 3.1 and 4.0 (P=0.39).

CONCLUSIONS

This study provides further evidence that I-FOBT is superior to G-FOBT. None of the three I-FOBTs studied appeared to be significantly better than the others.

Population-based screening for colorectal cancer using an immunochemical faecal occult blood test: a comparison of two invitation strategies

BACKGROUND

To date, there is no screening programme for colorectal cancer (CRC) in Flanders, Belgium. However, The European Code Against Cancer (2003) recommends a population-based approach for CRC screening. This study aimed to obtain information about potential participation rates for a population-based screening programme for CRC in Flanders, and to compare two invitation strategies.

METHODS

In 2009, a trial programme for CRC screening was set up in three Flemish areas for all average-risk people aged 50-74 years, using an immunochemical faecal occult blood test (iFOBT) with a cut-off value set at 75 ng/ml of haemoglobin. The faecal sampling set was sent at random by post (mail group) or provided by the general practitioner (GP group).

RESULTS

In total, 19,542 people were invited to participate. Of these, 8229 provided a faecal sample, resulting in an overall participation rate of 42.1%. Participation by mail and through the GP was 52.3% (95% CI, 51.3-53.2) and 27.7% (95% CI, 26.7-28.6), respectively. The difference of 24.6% was statistically significant (95% CI, 23.3-25.9, p<0.001). Before the reminder letter was sent and the other invitation strategy was offered, the overall participation rate was 26.5% (n=5176); 36.4% (95% CI, 35.5-37.4) for the mail group and 16.6% (95% CI, 15.8-17.3) for the GP group. The odds of participating in CRC screening was almost three times higher for people invited by mail as opposed to people invited through a GP (OR=2.96, 95% CI, 2.78-3.14, p<0.001). Women were more likely to participate in CRC screening than men (OR=1.22, 95% CI, 1.15-1.30, p<0.001). In addition, we found that inhabitants from residential (OR=1.98, 95% CI, 1.85-2.11) and rural (OR=2.90, 95% CI, 2.66-3.16) areas were more likely to participate than those in urban areas. Of the 8229 people who submitted a faecal sample, 435 (5.3%) had a positive iFOBT, and of those, CRC was diagnosed in 18 (5.7%) individuals. Compliance for follow-up colonoscopy was 72.9%, and did not differ between the mail (72.4%, 95% CI, 67.5-77.3) and GP groups (74.3, 95% CI, 66.2-82.5).

CONCLUSION

Inviting people for CRC screening by means of a direct-mail invitation, and including a faecal sampling set (iFOBT), results in much higher participation rates than inviting people through the GP.

Colonoscopy versus fecal immunochemical testing in colorectal-cancer screening

BACKGROUND

Colonoscopy and fecal immunochemical testing (FIT) are accepted strategies for colorectal-cancer screening in the average-risk population.

METHODS

In this randomized, controlled trial involving asymptomatic adults 50 to 69 years of age, we compared one-time colonoscopy in 26,703 subjects with FIT every 2 years in 26,599 subjects. The primary outcome was the rate of death from colorectal cancer at 10 years. This interim report describes rates of participation, diagnostic findings, and occurrence of major complications at completion of the baseline screening. Study outcomes were analyzed in both intention-to-screen and as-screened populations.

RESULTS

The rate of participation was higher in the FIT group than in the colonoscopy group (34.2% vs. 24.6%, P<0.001). Colorectal cancer was found in 30 subjects (0.1%) in the colonoscopy group and 33 subjects (0.1%) in the FIT group (odds ratio, 0.99; 95% confidence interval [CI], 0.61 to 1.64; P=0.99). Advanced adenomas were detected in 514 subjects (1.9%) in the colonoscopy group and 231 subjects (0.9%) in the FIT group (odds ratio, 2.30; 95% CI, 1.97 to 2.69; P<0.001), and nonadvanced adenomas were detected in 1109 subjects (4.2%) in the colonoscopy group and 119 subjects (0.4%) in the FIT group (odds ratio, 9.80; 95% CI, 8.10 to 11.85; P<0.001).

CONCLUSIONS

Subjects in the FIT group were more likely to participate in screening than were those in the colonoscopy group. On the baseline screening examination, the numbers of subjects in whom colorectal cancer was detected were similar in the two study groups, but more adenomas were identified in the colonoscopy group. (Funded by Instituto de Salud Carlos III and others; ClinicalTrials.gov number, NCT00906997.).

Are fecal immunochemical test characteristics influenced by sample return time? A population-based colorectal cancer screening trial

OBJECTIVES

Fecal immunochemical tests (FIT) are preferred over guaiac-based fecal occult blood testing as colorectal cancer (CRC) screening tool. However, hemoglobin (Hb) degradation over time may influence FIT outcome. We therefore evaluated the effect of sample return time on FIT performance characteristics in a population-based CRC screening trial.

METHODS

A representative random sample of the Dutch population (n=17,677), aged 50-74 years, was invited for FIT screening (OC-Sensor Micro; cutoff ≥ 50 ng Hb/ml). Sample return time was defined as the interval in days between fecal sampling and FIT laboratory delivery. Moreover, a random sample of positive FITs were selected to be stored at room temperature and re-tested every 3-4 days.

RESULTS

In total, 8,958 screenees fulfilled our inclusion criteria. The mean sample return time was 3 days (± 3). Overall, 792 screenees (8.8%) had a positive test. Between the sample return time groups, the positivity rate (PR) varied between 7.7 and 9.0%. No statistically significant associations were found between PR or detection rate (DR) and the different sample return time groups (P value=0.84 and 0.76, respectively). For the laboratory experiment, 71 positive FITs were stored at room temperature and re-tested with standard intervals. The mean daily fecal Hb decrease was 5.88% per day (95% confidence interval 4.78-6.96%). None of the positive FITs became negative before 10 days after fecal sampling.

CONCLUSIONS

This population-based CRC screening trial demonstrates that both the PR and DR of FITs do not decrease with prolonged sample return times up to 10 days. This means that a delay in sending the FIT back to the laboratory, of up to at least 1 week, does not necessitate repeat sampling in case of a negative test result. These data support the use of FIT-based screening as a reliable tool for nationwide CRC screening programs.

Screening for colorectal cancer: sense and sensibilities

PURPOSE

In this paper we investigate the reasons for non-participation in a trial programme for colorectal cancer (CRC) screening in Flanders. Besides, the feasibility and possibilities of a full-blown screening programme in Flanders are examined, given the context of a low participation rate in breast cancer screening.

METHODS

A trial programme for CRC screening was set up for all average-risk persons aged 50 to 74 years in three Flemish regions to obtain information about potential participation rates, and to compare two invitation strategies. Faecal samples were analysed for precursors of CRC using an immunochemical faecal occult blood test (iFOBT). A questionnaire was administered to participants and non-participants of the trial programme to find out whether and to what extent the taking of a sample of one's own stool is a taboo. This could be of great importance concerning the participation rate.

RESULTS

In total, 19,542 persons were invited to participate in the trial programme for CRC screening, of whom 18,541 were found to be eligible. The overall participation rate was 44.3%. The three regions varied in participation rates: with 60.9% in the most rural region to 34.3% in the most urban region. Of 2,000 questionnaires sent to participants, 1,385 were returned (69.3%). The response in the non-participants was 43.2%i (691 questionnaires of 1,600 returned).

CONCLUSIONS

A population-based screening programme for colorectal cancer by means of an iFOBT proves to be feasible, since adequate participation rates were obtained and because of the absence of a 'stool taboo' in Flanders.

Screening for colorectal cancer: established and emerging modalities

It has been estimated that >95% of cases of colorectal cancer (CRC) would benefit from curative surgery if diagnosis was made at an early or premalignant polyp stage of disease. Over the past 10 years, most developed nation states have implemented mass population screening programs, which are typically targeted at the older (at-risk) age group (>50-60 years old). Conventional screening largely relies on periodic patient-centric investigation, particularly involving colonoscopy and flexible sigmoidoscopy, or else on the fecal occult blood test. These methods are compromised by either low cost-effectiveness or limited diagnostic accuracy. Advances in the development of diagnostic molecular markers for CRC have yielded an expanding list of potential new screening modalities based on investigations of patient stool (for colonocyte DNA mutations, epigenetic changes or microRNA expression) or blood specimens (for plasma DNA mutations, epigenetic changes, heteroplasmic mitochondrial DNA mutations, leukocyte transcriptome profile, plasma microRNA expression or protein and autoantibody expression). In this Review, we present a critical evaluation of the performance data and relative merits of these various new potential methods. None of these molecular diagnostic methods have yet been evaluated beyond the proof-of-principle and pilot-scale study stage and it could be some years before they replace existing methods for population screening in CRC.

Molecular tests for colorectal cancer screening

Detecting and removing high-risk adenomas and early colorectal cancer (CRC) can reduce mortality of this disease. The noninvasive fecal occult blood test (FOBT; guaiac-based or immunochemical) is widely used in screening programs and although effective, it leaves room for improvement in terms of test accuracy. Molecular tests are expected to be more sensitive, specific and informative than current detection tests, and are promising future tools for CRC screening. This review provides an overview of the performances of DNA, RNA, and protein markers for CRC detection in stool and blood. Most emphasis currently is on DNA and protein markers. Among DNA markers there is trend to move away from mutation markers in favor of methylation markers. The recent boost in proteomics research leads to many new candidate protein markers. Usually in small series, some markers show better performance than the present FOBT. Evaluation in large well-controlled randomized trials is the next step needed to take molecular markers for CRC screening to the next level and warrant implementation in a screening setting.

Test performance of immunologic fecal occult blood testing and sigmoidoscopy compared with primary colonoscopy screening for colorectal advanced adenomas

Given the current increase in colorectal cancer screening, information on performance of screening tests is needed, especially in groups with a presumed lower test performance. We compared test performance of immunologic fecal occult blood testing (FIT) and pseudosigmoidoscopy with colonoscopy for detection of advanced adenomas in an average risk screening population. In addition, we explored the influence of gender, age, and location on test performance. FIT was collected prior to colonoscopy with a 50 ng/mL cutoff point. FIT results and complete colonoscopy findings were available from 329 subjects (mean age: 54.6 ± 3.7 years, 58.4% women). Advanced adenomas were detected in 38 (11.6%) of 329 subjects. Sensitivity for advanced adenomas of FIT and sigmoidoscopy were 15.8% (95% CI: 6.0-31.3) and 73.7% (95% CI: 56.9-86.6), respectively. No sensitivity improvement was obtained using the combination of sigmoidoscopy and FIT. Mean fecal hemoglobin in FIT positives was significantly lower for participants with only proximal adenomas versus those with distal ones (P = 0.008), for women versus men (P = 0.023), and for younger (<55 years) versus older (≥55 years) subjects (P = 0.029). Sensitivities of FIT were 0.0% (95% CI: 0.0-30.9) in subjects with only proximal versus 21.4% (95% CI: 8.3-41.0) in those with distal nonadvanced adenomas; 5.3% (95% CI: 0.0-26.0) in women versus 26.3% (95% CI: 9.2-51.2) in men; 9.5% (95% CI: 1.2-30.4) in younger versus 23.5% (95% CI: 6.8-49.9) in older subjects. Sigmoidoscopy had a significantly higher sensitivity for advanced adenomas than FIT. A single FIT showed very low sensitivity, especially in subjects with only proximal nonadvanced adenomas, in women, and in younger subjects. This points to the existence of "low" FIT performance in subgroups and the need for more tailored screening strategies.

Cancer screening in people who have chronic disease: the example of kidney disease

Cancer screening in people with chronic illness has been the subject of considerable debate recently. Despite the increased incidence of cancer and higher risk of cancer deaths in selected populations, such as those with kidney disease, the benefits-to-harms ratio of cancer screening is uncertain and is likely to be different to people without chronic illnesses because of the expected higher competing risk of death from disease other than cancer, and a higher risk of complications associated with the screening, the diagnostic, and the treatment processes. Using kidney disease as an example, the authors reviewed the current evidence for early cancer detection through screening in people with two or more coexistent chronic diseases, discussed the accepted principles underpinning cancer screening, and the applicability of these concepts to individuals with chronic disease. This review suggests that future research that evaluates the screening test accuracy, quality of life of having cancer, and cancer treatment effectiveness, targeting those with chronic illnesses are necessary for the development of an effective, safe, and acceptable cancer screening program among people with two or more chronic diseases.

Cost-effectiveness of mass screening for colorectal cancer: choice of fecal occult blood test and screening strategy

BACKGROUND

Colorectal cancer is a major cause of mortality. This gives high public health priority to mass screening using a noninvasive, fecal occult blood test of asymptomatic individuals. A positive test selects those who should undergo colonoscopy to ensure early detection of colorectal cancer. Guaiac fecal occult blood test has low sensitivity. Automated immunochemical tests that measure the fecal human hemoglobin concentration are more sensitive and can be simplified as a 1- to 3-sample format with optimum cutoff points.

OBJECTIVE

The aim was to improve the sensitivity of the test by choosing an accurate format (1- to 3-sample and optimum hemoglobin concentration) while maintaining acceptable specificity and avoiding alteration of the screening program in terms of quality of life and economic outputs.

METHODS

We used a Markov model to estimate the cost-effectiveness of a screening program for a population of 100,000 asymptomatic individuals by use of immunological fecal tests with different cutoffs, leading to different sensitivity/specificity ratios, and to compare its incremental cost-effectiveness ratio compared with the guaiac fecal test program.

RESULTS

The results suggest that a 3-sample immunological test with 50 ng/mL as a positive cutoff is cost-effective. It provides more asymptomatic cancer detection without significantly increasing normal colonoscopies.

CONCLUSION

This format should be prospectively evaluated in mass screening.

A higher detection rate for colorectal cancer and advanced adenomatous polyp for screening with immunochemical fecal occult blood test than guaiac fecal occult blood test, despite lower compliance rate. A prospective, controlled, feasibility study

Immunochemical fecal occult blood test (FIT) is a new colorectal cancer (CRC) screening method already recommended by the American screening guidelines. We aimed to test the feasibility of FIT as compared to guaiac fecal occult blood test (G-FOBT) in a large urban population of Tel Aviv. Average-risk persons, aged 50-75 years, were offered FIT or G-FOBT after randomization according to the socioeconomic status of their clinics. Participants with positive tests underwent colonoscopy. Participants were followed through the Cancer Registry 2 years after the study. Hemoccult SENSA™ and OC-MICRO™ (three samples, 70 ng/ml threshold) were used. FIT was offered to 4,657 persons (Group A) and G-FOBT to 7,880 persons (Group B). Participation rate was 25.9% and 28.8% in Group A and B, respectively (p < 0.001). Positivity rate in Group A and B was 12.7% and 3.9%, respectively (p < 0.001). Cancer found in six (0.49%) and eight (0.35%) patients of Group A and B, respectively (NS). Cancer registry follow-up found missed cancer in five (0.22%) cases of Group B and none in Group A (NS). The sensitivity, specificity, negative and positive predictive value for cancer in Group A and B were 100%, 85.9%, 100%, 3.9% and 61.5%, 96.4%, 99.8%, 9.1%, respectively. There was increased detection of advanced adenomatous polyp (AAP) by FIT, irrespective of age, gender, and socioeconomic status (Per Protocol: odds ratio 2.69, 95% confidence interval 1.6-4.5; Intention to Screen: odds ratio 3.16, 95% confidence interval 1.8-5.4). FIT is feasible in urban, average-risk population, which significantly improved performance for detection of AAP and CRC, despite reduced participation.

Immunochemical faecal occult blood tests have superior stability and analytical performance characteristics over guaiac-based tests in a controlled in vitro study

Aims

The aims of this study were (1) to determine the measurement accuracy of a widely used guaiac faecal occult blood test (gFOBT) compared with an immunochemical faecal occult blood test (iFOBT) during in vitro studies, including their analytical stability over time at ambient temperature and at 4°C; and (2) to compare analytical imprecision and other characteristics between two commercially available iFOBT methods.

Methods

Faecal specimens from healthy volunteers negative for occult blood were spiked with red cell lysate to give concentrations of 0 (A), 2.5 (B) and 4.5 (C) mg Hb/g faeces respectively. Samples from each pool were then tested by nine blinded assessors in order to determine the measurement accuracy. Sample stability for the gFOBT at ambient temperature (18°C) was determined by repeating the gFOBT analysis on faecal samples (A, B and C) consecutively for 7 days. Stability for the iFOBT was tested on spiked faecal samples stored at 4°C and also at ambient temperature (18°C). Testing for other analytical performance characteristics including sample carryover and imprecision was performed for both iFOBT methods.

Results

Nine blinded assessors using gFOBT achieved correct readings for eight of nine samples from Pool A, five of nine from Pool B and seven of nine from Pool C. Overall, the sensitivity and specificity of gFOBT were 67% and 89% respectively. No discrepant results were detected with iFOBT. Faecal samples applied to gFOBT cards immediately postcollection gave positive results for the next 7 days only for pool C. In contrast, the results of iFOBT remained stable up to 14 days at 18°C. The within-run imprecision and sample carryover showed robust results with both iFOBT methods.

Conclusions

The superior analytical stability and measurement accuracy demonstrated by the iFOBT in this in vitro study confers advantages over traditional qualitative gFOBTs and supports their suitability for more widespread use in population-based colorectal-cancer screening programmes.

Effectiveness of the immunofecal occult blood test for colorectal cancer screening in a large population

BACKGROUND

Guaiac tests are the most widely used tests to detect colorectal cancer (CRC). However, their sensitivity is relatively low and results may be affected by various factors. Immunofecal occult blood test (IFOBT) is specific for human hemoglobin and does not require dietary restrictions.

AIMS

The aim of this study was to evaluate the effectiveness of IFOBT for the screening of precancerous lesions and CRC.

METHODS

From July 2006 to June 2007, IFOBT was performed on 5,919 adults who received periodic health examinations in our hospital. The positive cases were examined by colonoscopy and a double-contrast barium enema. Diagnosis was confirmed by histopathological analysis.

RESULTS

Positive IFOBT was detected in 314 of 5,919 cases (5.30%). Further examinations were made in 264 IFOBT-positive cases. Of these, 116 cases with colorectal cancer (16 cases) or precancerous lesions (94 cases with colorectal adenomatous polyps and 6 cases with active ulcerative colitis) were detected. The total detection rate of CRC and precancerous lesions was 43.94% (116/264). TNM classification of 16 CRC cases was as follows: TNM I in eight cases (50.00%), TNM II in seven cases (43.75%) and TNM III in one case (6.25%), indicating IFOBT can detect CRC in the early stages.

CONCLUSION

Regular IFOBT can detect precancerous lesions and CRC in early stages and can thus reduce mortality from CRC.

Higher fecal immunochemical test cutoff levels: lower positivity rates but still acceptable detection rates for early-stage colorectal cancers

BACKGROUND

Adjusting the threshold for positivity of quantitative fecal immunochemical tests (FIT) allows for controlling the number of follow-up colonoscopies in a screening program. However, it is unknown to what extent higher cutoff levels affect detection rates of screen-relevant neoplasia. This study aimed to assess the effect of higher cutoff levels of a quantitative FIT on test positivity rate and detection rate of early-stage colorectal cancers (CRC).

METHODS

Subjects above 40 years old scheduled for colonoscopy in 5 hospitals were asked to sample a single FIT (OC sensor) before colonoscopy. Screen-relevant neoplasia were defined as advanced adenoma or early-stage cancer (stage I and II). Positivity rate, sensitivity, and specificity were evaluated at increasing cutoff levels of 50 to 200 ng/mL.

RESULTS

In 2,145 individuals who underwent total colonoscopy, 79 patients were diagnosed with CRC, 38 of which were with early-stage disease. Advanced adenomas were found in 236 patients. When varying cutoff levels from ≥ 50 to ≥ 200 ng/mL, positivity rates ranged from 16.5% to 10.2%. With increasing cutoff levels, sensitivity for early-stage CRCs and for screen-relevant neoplasia ranged from 84.2% to 78.9% and 47.1% to 37.2%, respectively.

CONCLUSIONS

Higher FIT cutoff levels substantially decrease test positivity rates with only limited effects on detection rates of early-stage CRCs. However, spectrum bias resulting in higher estimates of sensitivity than would be expected in a screening population may be present.

IMPACT

Higher cutoff levels can reduce strain on colonoscopy capacity with only a modest decrease in sensitivity for curable cancers.

Comparison of guaiac-based and quantitative immunochemical fecal occult blood testing in a population at average risk undergoing colorectal cancer screening

OBJECTIVES

Although some studies have shown that the quantitative, immunochemical fecal occult blood test (FOBT) (qFIT) has better performance characteristics than the standard guaiac-based FOBT (GT) for identifying advanced colorectal neoplasia (ACRN), there is limited information on test performance of these tests in average-risk populations.

METHODS

Seven hundred seventy consecutive average-risk patients from four centers who were undergoing screening colonoscopy also provided stool samples. Stool specimens from three consecutive bowel movements were applied to a hemoccult II test card (Beckman Coulter, Fullerton, CA) and OC-SENSA MICRO (Eiken Chemical, Tokyo, Japan) sampling probes at the same time. We measured the diagnostic value of the qFIT for detecting an ACRN by using three criteria: sensitivity, specificity, and likelihood ratios. A receiver operating characteristic curve for determining the qFIT cutoff values and the number of tests that best discriminated between ACRNs and other findings were determined.

RESULTS

Seventy-eight ACRNs were identified during colonoscopy. At all hemoglobin thresholds, the sensitivity of the qFIT was higher than that of the GT for cancer or ACRN. The sensitivity and specificity of the GT for detecting advanced adenomas, cancer, and ACRNs were 13.6%/92.4%, 30.8%/92.4%, and 16.7%/92.9%, respectively. Using the 100 ng/ml cut point and three-sample qFIT results, the sensitivity and specificity of the qFIT for detecting advanced adenomas, cancer, and ACRNs were 33.9%/90.6%, 84.6%/89.8%, and 43.7%/91.9%, respectively. The area under the curve for cancer indicated that using either 2 or 3 tests provided the best discrimination for cancer.

CONCLUSIONS

The qFIT provides a higher sensitivity for detecting ACRN and cancer than the GT, and has an acceptable specificity that significantly reduces the need for colonoscopic evaluation in the screened population.

Performance improvements of stool-based screening tests

Stool testing is a widely accepted, non-invasive, technique for colorectal cancer (CRC) screening. Guaiac-based faecal occult blood test (gFOBT) screening has been proven to decrease CRC-related mortality; however gFOBT is hampered by a low sensitivity. Faecal immunochemical tests (FITs) have several advantages over gFOBT. First of all, FIT has a better sensitivity and higher uptake. Furthermore, the quantitative variant of the FIT allows choices on cut-off level for test-positivity according to colonoscopy resources available, personal risk profile, and/or intended detection rate in the screened population. Stool-based DNA (sDNA) tests aiming at the detection of specific DNA alterations may improve detection of CRC and adenomas compared to gFOBT screening, but large-scale population based studies are lacking. This review focuses on factors influencing test performance of those three stool based screening tests.

Diagnostic accuracy of immunochemical versus guaiac faecal occult blood tests for colorectal cancer screening

BACKGROUND

Immunochemical tests show important advantages over chemical-based faecal occult blood tests (FOBT) for colorectal cancer (CRC) screening, but comparison studies are limited. This study was performed to compare the accuracy of a sensitive immunochemical test with the guaiac test for detecting significant neoplasia (advanced adenomas and CRC) in an average-risk population.

METHODS

A random sample of 2288 asymptomatic subjects 50-79 years of age was prospectively included. Participants received three cards of the guaiac test, one sample of a latex-agglutination test (haemoglobin cut-off 50 ng/ml), and an invitation to undergo colonoscopy. Test sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated in 1756 compliers.

RESULTS

Immunochemical and guaiac tests were positive in 143 (8.1%) and 62 (3.5%) subjects, respectively. Complete colonoscopy, performed in 402 participants (158 FOBT+ and 244 FOBT-), detected 14 (0.8%) patients with CRC and 49 (2.8%) with advanced adenomas. The immunochemical and guaiac tests for significant colorectal neoplasia showed sensitivities of 61% versus 23.8%, specificities of 95.1% versus 97.7%, PPVs of 43.4% versus 39.0%, and NPVs of 97.5% versus 95.4%, respectively. Proximal significant neoplasms were more frequently detected with the immunochemical test (85% vs. 15%) The relative risk for detecting significant neoplasia was superior in patients with a positive immunochemical test (RR 16.93; CI 7.94-36.10) than with a positive guaiac test (RR 3.34; CI 2.17-5.15).

CONCLUSION

A sensitive immunochemical test is markedly superior to the guaiac test for detecting significant colorectal neoplasia, and should be considered the first-choice FOBT for CRC screening in the average-risk population.

Cumulative evaluation of a quantitative immunochemical fecal occult blood test to determine its optimal clinical use

BACKGROUND

Quantified, human hemoglobin (Hb)-specific, immunochemical fecal occult blood test (IFOBT) measurements are now used for colorectal cancer (CRC) screening. The objective was to evaluate sensitivity and specificity for CRC and advanced adenomatous polyps (APs) by the fecal Hb threshold used to determine a positive test and the number of IFOBTs prepared per test, so as to determine the least number of colonoscopies required to detect a neoplasm.

METHODS

Cumulative data were analyzed from a prospective cross-sectional double-blind study of 1682 consecutive, ambulatory, nonbleeding colonoscopy patients who volunteered for IFOBTs, most of above average risk, from 3 ambulatory-endoscopy centers. Fecal Hb was measured in 3 samples and analyzed by an automated instrument, and the highest result >or=50 ng Hb/mL of buffer was related to findings.

RESULTS

Colonoscopy identified CRC in 20 patients and advanced APs in 129. Sensitivity for either was best when any of 3 tests had >or=50 ng Hb/mL of buffer; sensitivity was 61.1% (95% confidence interval [CI], 53.2-68.9), and specificity was 87.8% (95% CI, 86.2-89.4). Positive tests identified 100% of CRCs and 55% of advanced APs every 3.1 colonoscopies. Sensitivity of a single test at the commonly used 100-ng Hb/mL threshold was lower at 31.5% (95% CI, 24.1-39.0) (P<.001), but specificity was higher at 96.4% (95% CI, 95.5-97.3) (P<.001). Positive tests identified 65% of CRCs and 26.4% of advanced APs every 2.2 colonoscopies.

CONCLUSIONS

The fecal Hb cutoff chosen by the screener and the number of samples collected per patient determine sensitivity and specificity for CRC/advanced AP; these factors determine the number of colonoscopies needed for positive tests and neoplasia yield. This information provides guidelines for IFOBT screening. Limitations are 1-time screening and most examinees not being at average risk for CRC.

Prediction of flare-ups of ulcerative colitis using quantitative immunochemical fecal occult blood test

AIM: To examine the feasibility of predicting the flare-up of ulcerative colitis (UC) before symptoms emerge using the immunochemical fecal occult blood test (I-FOBT).

METHODS: We prospectively measured fecal hemoglobin concentrations in 78 UC patients using the I-FOBT every 1 or 2 mo.

RESULTS: During a 20 mo-period, 823 fecal samples from 78 patients were submitted. The median concentration of fecal hemoglobin was 41 ng/mL (range: 0-392 500 ng/mL). There were three types of patients with regard to the correlation between I-FOBT and patient symptoms; the synchronous transition type with symptoms (44 patients), the unrelated type with symptoms (19 patients), and the flare-up predictive type (15 patients). In patients with the flare-up predictive type, the values of I-FOBT were generally low during the study period with stable symptoms. Two to four weeks before the flare-up of symptoms, the I-FOBT values were high. Thus, in these patients, I-FOBT could predict the flare-up before symptoms emerged.

CONCLUSION: Flare-up could be predicted by I-FOBT in approximately 20% of UC patients. These results warrant periodical I-FOBT in UC patients.

A retrospective study of immunochemical fecal occult blood testing for colorectal cancer detection

BACKGROUND

Colonoscopic examination is the common pathway for positive screening tests detecting colorectal lesions. We evaluated a specific, quantitative high-throughput automatic immunochemical fecal occult blood test (Auto iFOBT) method for colorectal cancer (CRC) screening and to determine its concordance with physician assessments informed by complete colonoscopy, the gold-standard technique for evaluation of the colonic mucosa.

METHODS

1200 CRC symptomatic patients were recruited for a retrospective investigation. Colorectal neoplasia were localized by colonoscopy and cancer outcomes were enumerated according to severity. In addition, stool samples were collected and analyzed by Auto iFOBT to derive sensitivity, specificity, and positive predictive value. Qualitative colonoscopy and Auto iFOBT results were correlated, as were cancer severities and quantitative hemoglobin concentrations.

RESULTS

Ninety-one patients were found positive for CRC; 50 mucosal, 20 submucosal, and 21 advanced. At standard cutoff, sensitivity was 60%, 90%, and 95%, respectively. Specificity and positive predictive value for all neoplasia and cancers were 89.6% and 86.4%, and 60.9% and 33.7%, respectively. Cancer severities could be approximated roughly according to hemoglobin concentrations.

CONCLUSIONS

Specific qualitative 2-day Auto iFOBT is an accurate tool for the detection of colorectal cancer and therefore provides the basis for a large-scale screening program.

Can patients at high risk for significant colorectal neoplasms and having normal quantitative faecal occult blood test postpone elective colonoscopy?

BACKGROUND

Common reasons for elective screening and surveillance colonoscopy, at predetermined intervals, are family or personal history of colorectal cancer (CRC) or advanced adenoma (AAP). Quantified, human haemoglobin (Hb)-specific, immunochemical faecal occult blood tests (I-FOBT) detect bleeding.

AIM

To determine I-FOBT sensitivity for CRC or AAP before elective colonoscopy in patients at high-risk of cancer or advanced adenoma.

METHODS

Prospective double-blind study of 1000 ambulatory asymptomatic high-risk patients (555 family history of CRC, 445 surveillance for past neoplasm), who prepared three I-FOBTs before elective colonoscopy. I-FOBTs quantified as ngHb/mL of buffer by OC-MICRO instrument and results >or=50 ngHb/mL considered positive.

RESULTS

At colonoscopy, eight patients had CRC, 64 others had AAP. Sensitivity for CRC and/or AAP was the highest, 65.3% (95% CI 54.3, 76.3), when any of the three I-FOBTs was >or=50 ngHb (15.4%), with specificity of 87.5% (95% CI 86.4, 90.5) identifying all CRCs and 62% of AAPs.

CONCLUSIONS

All cancers or an AAP were detected every third I-FOBT-positive colonoscopy (47/154), so colonoscopy was potentially not needed at this time in 84.6% (846 patients). I-FOBT screening might provide effective supervision of high-risk patients, delaying unnecessary elective colonoscopies. This favourable evaluation needs confirmation and cost-benefit study by risk-group.

[Influence of the pre-analytical specimen storage conditions on the fecal occult blood test results]

BACKGROUND

Korean national cancer screening program selected fecal occult blood test (FOBT) as a primary screening method of colorectal carcinoma in adult > or =50 yr old irrespective of symptom. Notice to pre-analytical errors is especially important for the FOBT because examinees collect and submit their specimens to laboratories by themselves. We examined the influences of the fecal storage temperatures, durations and with or without buffer on the FOBT results.

METHODS

Thirty FOBT-positive specimens above 100 ng/mL were used for the study from July to August 2008. Quantitative FOBT was performed with OC-sensors II (Eiken Chemical Co., Japan). Each specimen was divided into 4 groups. Two groups in plastic buffer-free containers were kept either at 4 degrees C or room temperature (25-28 degrees C), respectively. Another two groups in buffer-tubes were also kept either at 4 degrees C or room temperature. Each group was repeatedly examined with same method every 24 hr up to 120 hr.

RESULTS

Eleven specimens (36.7%) in buffer-free containers converted to negative results (below the 100 ng/mL) after 24 hr and 17 specimens (56.7%) did after 48 hr at room temperature. Ten specimens (33.3%) in buffer-free containers converted to negative after 48 hr at 4 degrees C. Specimens contained in buffer-tubes showed little change; 3 specimens (10.0%) at room temperature and no specimen at 4 degrees C showed negative conversions after 48 hr.

CONCLUSIONS

Buffer-tube minimizes false negative FOBT results during pre-analytical delay of specimen. The examinees using buffer-free containers need to be educated to hand in their specimens to laboratories as soon as possible.

Cutoff value determines the performance of a semi-quantitative immunochemical faecal occult blood test in a colorectal cancer screening programme

Background:

The cutoff of semi-quantitative immunochemical faecal occult blood tests (iFOBTs) influences colonoscopy referrals and detection rates. We studied the performance of an iFOBT (OC-Sensor) in colorectal cancer (CRC) screening at different cutoffs.

Methods:

Dutch screening participants, 50–75 years of age, with average CRC risk and an iFOBT value ⩾50 ng ml⁻¹ were offered colonoscopy. The detection rate was the percentage of participants with CRC or advanced adenomas (⩾10 mm, ⩾20% villous, high-grade dysplasia). The number needed to scope (NNTScope) was the number of colonoscopies to be carried out to find one person with CRC or advanced adenomas.

Results:

iFOBT values ⩾50 ng ml⁻¹ were detected in 526 of 6157 participants (8.5%) and 428 (81%) underwent colonoscopy. The detection rate for advanced lesions (28 CRC and 161 with advanced adenomas) was 3.1% (95% confidence interval: 2.6–3.5%) and the NNTScope was 2.3. At 75 ng ml⁻¹, the detection rate was 2.7%, the NNTScope was 2.0 and the CRC miss rate compared with 50 ng ml⁻¹ was <5% (N=1). At 100 ng ml⁻¹, the detection rate was 2.4% and the NNTScope was <2. Compared with 50 ng ml⁻¹, up to 200 ng ml⁻¹ CRC miss rates remained at 16% (N=4).

Conclusions:

Cutoffs below the standard 100 ng ml⁻¹ resulted in not only higher detection rates of advanced lesions but also more colonoscopies. With sufficient capacity, 75 ng ml⁻¹ might be advised; if not, up to 200 ng ml⁻¹ CRC miss rates are acceptable compared with the decrease in performed colonoscopies.

False negative fecal occult blood tests due to delayed sample return in colorectal cancer screening

Delayed return of immunochemical fecal occult blood test (iFOBT) samples to a laboratory might cause false negatives because of hemoglobin degradation. Quantitative iFOBT's became increasingly more accepted in colorectal cancer screening. Therefore, we studied the effects of delay between sampling and laboratory delivery on iFOBT performance. IFOBT positivity (>or=50 ng/ml hemoglobin) in colorectal cancer screening participants without delay between sampling and laboratory delivery (<5 days), was compared with positivity in participants with >or=5 and >or=7 days delay. Additionally, positive tests were stored at room temperature and retested 5 times within 10-14 days. The sampling date was reported by 61% (n = 3,767) of the participants: in 19% delay was >or=5 days and in 5% >or=7 days. Compared with no-delay, the adenoma detection rate was already significantly decreased after >or=5 days delay (OR 0.6; 95%CI 0.4-0.9). We retested iFOBT samples of 170 positives of which 139 (82%) had a colonoscopy: 45 (32%) had advanced adenomas (not colorectal cancer) and 8 (6%) had colorectal cancer. Mean daily fecal hemoglobin decrease was 29 ng/ml (S.D. 38 and median 11 ng/ml). In patients with advanced adenomas, hemoglobin in the sample was <50 ng/ml in 5 (11%) 2-3 days after the initial test and in 16 (36%) after 10-14 days. Seven days after the initial test, 2 (25%) colorectal cancer patients became false negative. Both had stage I colorectal cancer and initial values below 100 ng/ml, where the average for stage I is 532 ng/ml. Delay in sample return increased false negative immunochemical FOBT's. Mainly precursor lesions, but also colorectal cancer, will be missed due to delayed sample return.

[Chemical or immunological tests for the detection of fecal occult blood in colorectal cancer screening?]

Colorectal cancer (CRC) can be prevented by screening programs in the population at average risk (men and women aged between 50 and 74 years) and at high risk (first degree relatives, CRC hereditary syndromes and chronic inflammatory bowel disease). Early CRC (with submucosal invasion) and advanced adenomas (size > or =10mm, with severe dysplasia or >20% villous component) produce intermittent microscopic blood losses that can be detected through chemical and immunological testing for fecal occult blood (C-FOBT and I-FOBT). Among the screening strategies in the population at average risk, annual or biannual fecal occult blood testing is the most widely used due to its non-invasiveness and low cost. Four randomized clinical trials have shown that annual or biannual screening with guaiac-based tests (C-FOBT) reduces overall mortality due to CRC by 16% and CRC incidence by 20% and 17% respectively. However, these tests have major drawbacks, especially their low sensitivity in detecting early CRC and advanced adenoma, their lack of specificity in detecting human hemoglobin (Hb), and their high fecal Hb detection threshold (>300microgHb/gfeces). In the last few years, major developments have occurred in immunological tests (I-FOBT), based on an antigen-antibody reaction that specifically detects human Hb, and these tests are currently available as an alternative to C-FOBT. Their main advantages are as follows: firstly, I-FOBT specifically detect human Hb in stools and at much lower levels (40-300microgHb/gfeces) than C-FOBT; secondly, automated analysis avoids subjectivity in reading qualitative tests and allows large population groups to be studied in a short time, making I-FOBT ideal for population-based screening; thirdly, I-FOBT fairly accurately selects individuals for colonoscopy so that approximately half of patients with an I-FOBT test show clinically significant colorectal neoplasia (advanced adenoma or invasive CRC); fourthly, the cut-off point for fecal Hb detection can be modified, depending on the availability of endoscopic resources; fifthly, when cut-off points for fecal Hb of 50-150microgHb/gfeces are used, more than twice the number of CRC and advanced adenomas are detected than with C-FOBT, with a reasonable false-positive rate; and sixthly, I-FOBT are better accepted by the population due to their simplicity and ease of use, increasing participation in screening programs. For all these reasons, the current recommendation is that the new quantitative I-FOBT tests replace C-FOBT tests when the strategy of population-based screening through annual or biannual fecal occult blood testing is considered.

Screening for colorectal cancer: random comparison of guaiac and immunochemical faecal occult blood testing at different cut-off levels

Immunochemical faecal occult blood testing (FIT) provides quantitative test results, which allows optimisation of the cut-off value for follow-up colonoscopy. We conducted a randomised population-based trial to determine test characteristics of FIT (OC-Sensor micro, Eiken, Japan) screening at different cut-off levels and compare these with guaiac-based faecal occult blood test (gFOBT) screening in an average risk population. A representative sample of the Dutch population (n=10 011), aged 50–74 years, was 1 : 1 randomised before invitation to gFOBT and FIT screening. Colonoscopy was offered to screenees with a positive gFOBT or FIT (cut-off 50 ng haemoglobin/ml). When varying the cut-off level between 50 and 200 ng ml⁻¹, the positivity rate of FIT ranged between 8.1% (95% CI: 7.2–9.1%) and 3.5% (95% CI: 2.9–4.2%), the detection rate of advanced neoplasia ranged between 3.2% (95% CI: 2.6–3.9%) and 2.1% (95% CI: 1.6–2.6%), and the specificity ranged between 95.5% (95% CI: 94.5–96.3%) and 98.8% (95% CI: 98.4–99.0%). At a cut-off value of 75 ng ml⁻¹, the detection rate was two times higher than with gFOBT screening (gFOBT: 1.2%; FIT: 2.5%; P<0.001), whereas the number needed to scope (NNscope) to find one screenee with advanced neoplasia was similar (2.2 vs 1.9; P=0.69). Immunochemical faecal occult blood testing is considerably more effective than gFOBT screening within the range of tested cut-off values. From our experience, a cut-off value of 75 ng ml⁻¹ provided an adequate positivity rate and an acceptable trade-off between detection rate and NNscope.

Immunochemical faecal occult blood test: number of samples and positivity cutoff. What is the best strategy for colorectal cancer screening?

Immunochemical faecal occult blood tests have shown a greater sensitivity than guaiac test in colorectal cancer screening, but optimal number of samples and cutoff have still to be defined. The aim of this multicentric study was to evaluate the performance of immunochemical-based screening strategies according to different positivity thresholds (80, 100, 120 ng ml(-1)) and single vs double sampling (one, at least one, or both positive samples) using 1-day sample with cutoff at 100 ng ml(-1) as the reference strategy. A total of 20 596 subjects aged 50-69 years were enrolled from Italian population-based screening programmes. Positivity rate was 4.5% for reference strategy and 8.0 and 2.0% for the most sensitive and the most specific strategy, respectively. Cancer detection rate of reference strategy was 2.8 per thousand, and ranged between 2.1 and 3.4 per thousand in other strategies; reference strategy detected 15.6 per thousand advanced adenomas (range=10.0-22.5 per thousand). The number needed to scope to find a cancer or an advanced adenoma was lower than 2 (1.5-1.7) for the most specific strategies, whereas it was 2.4-2.7, according to different thresholds, for the most sensitive ones. Different strategies seem to have a greater impact on adenomas rather than on cancer detection rate. The study provides information when deciding screening protocols and to adapt them to local resources.

Random comparison of guaiac and immunochemical fecal occult blood tests for colorectal cancer in a screening population

BACKGROUND & AIMS

Despite poor performance, guaiac-based fecal occult blood tests (G-FOBT) are most frequently implemented for colorectal cancer screening. Immunochemical fecal occult blood tests (I-FOBT) are claimed to perform better, without randomized comparison in screening populations. Our aim was to randomly compare G-FOBT with I-FOBT in a screening population.

METHODS

We conducted a population-based study on a random sample of 20,623 individuals 50-75 years of age, randomized to either G-FOBT (Hemoccult-II) or I-FOBT (OC-Sensor). Tests and invitations were sent together. For I-FOBT, the standard cutoff of 100 ng/ml was used. Positive FOBTs were verified with colonoscopy. Advanced adenomas were defined as >or=10 mm, high-grade dysplasia, or >or=20% villous component.

RESULTS

There were 10,993 tests returned: 4836 (46.9%) G-FOBTs and 6157 (59.6%) I-FOBTs. The participation rate difference was 12.7% (P < .01). Of G-FOBTs, 117 (2.4%) were positive versus 339 (5.5%) of I-FOBTs. The positivity rate difference was 3.1% (P < .01). Cancer and advanced adenomas were found, respectively, in 11 and 48 of G-FOBTs and in 24 and 121 of I-FOBTs. Differences in positive predictive value for cancer and advanced adenomas and cancer were, respectively, 2.1% (P = .4) and -3.6% (P = .5). Differences in specificities favor G-FOBT and were, respectively, 2.3% (P < .01) and -1.3% (P < .01). Differences in intention-to-screen detection rates favor I-FOBT and were, respectively, 0.1% (P < .05) and 0.9% (P < .01).

CONCLUSIONS

The number-to-scope to find 1 cancer was comparable between the tests. However, participation and detection rates for advanced adenomas and cancer were significantly higher for I-FOBT. G-FOBT significantly underestimates the prevalence of advanced adenomas and cancer in the screening population compared with I-FOBT.

Comparison of an established simple office-based immunological FOBT with fecal tumor pyruvate kinase type M2 (M2-PK) for colorectal cancer screening: prospective multicenter study

OBJECTIVES

The immunological fecal occult blood test (IFOBT) has established itself as a more precise marker for colorectal cancer (CRC) screening than traditional guaiac-based FOBT. The simpler, cheaper, and more convenient newer office-based IFOBTs have been validated for diagnosing CRC. Dimeric isoenzyme of pyruvate kinase, M2-PK, expressed by tumor cells, has as well been proposed as a screening tool for CRC. This is the first study comparing fecal M2-PK as a screening biomarker for CRC against previously evaluated office-based IFOBT and colonoscopy.

METHODS

Six hundred forty consecutive subjects (symptomatic, as well as for CRC screening) referred for colonoscopy for various indications across five centers in Germany provided the stool samples for performing M2-PK and an immunochemical FOB strip test. The IFOBT used was a rapid immunochromatographic assay for detection of fecal hemoglobin. For M2-PK, a commercially available sandwich enzyme-linked immunosorbent assay (ELISA) was used. The M2-PK test needs 6 h, while the office-based test can be read in just 10 min and is five times cheaper.

RESULTS

Office-based IFOBT had sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios (LR) of 64.5, 96.3, 72.0, 94.9, 17.5, and 0.4 for diagnosing colorectal neoplasia (CRN), while the above performance characteristics for M2-PK at a cutoff value of 4 U/mL were 72.4, 73.8, 29.0, 94.8, 2.8, and 0.8 respectively.

CONCLUSIONS

This office-based IFOBT was found to have significantly higher specificity, PPV, and positive LR as compared with M2-PK. IFOBT proved to be a convenient, noncumbersome, quick, and cheap tool in patients with above-average risk for detection of CRN.

Nicht-invasive Diagnostik kolorektaler Tumore – Hat der Guaiac-Test ausgedient? / Non-invasive detection of colorectal cancer – do we still need the guaiac-based fecal occult blood test?

Aufgrund der leichten Handhabung und des Nachweises einer Mortalitätssenkung gilt der Nachweis von okkultem Blut (FOBT) im Stuhl derzeit als das am weitesten verbreitete Screeningverfahren für das kolorektale Karzinom. Als nachteilig erweisen sich allerdings eine unzureichende Sensitivität, insbesondere beim Nachweis früher Stadien und eine nach wie vor geringe Akzeptanz in der Bevölkerung. Vorläufige Daten zum Nachweis von Calprotectin oder der Tumor-M2-PK im Stuhl ließen bessere Screeningeigenschaften erwarten. Aber auch hier schränkt die geringe Sensitivität für frühe Vorstufen und unzureichende Spezifität mit zu erwartenden hohen Folgekosten die Tauglichkeit der Tests deutlich ein. Die kürzlich entwickelten immunologischen FOBTs (I-FOBT) erweisen sich als spezifischer und sensitiver. Sie beruhen auf dem Nachweis von humanem Hämoglobin mittels spezifischer Antikörper und sind somit unabhängig von diätetischen oder medikamentösen Faktoren, was zu einer deutlich besseren Akzeptanz führt. Sie gelten derzeit als kosteneffektivste Verfahren unter den nichtinvasiven Screeningmaßnahmen. Der Nachweis von Tumor-DNA im Stuhl eröffnet eine neue Ära zum frühzeitigen Nachweis kolorektaler Karzinome. Erste kleinere Studien weisen auf eine sehr gute Sensitivität dieser Verfahren hin. Sie lagen für kolorektale Karzinome zwischen 62–91% und für Adenome zwischen 26–73% bei mit 93–100% sehr guter Spezifität. Als nachteilig im Vergleich zu den derzeit verfügbaren Screeningtests erweisen sich allerdings die vergleichsweise hohen Kosten.

As tests evolve and costs of cancer care rise: reappraising stool-based screening for colorectal neoplasia

BACKGROUND

Colorectal cancer screening and treatment are rapidly evolving. Aims To reappraise stool-based colorectal cancer screening in light of changing test performance characteristics, lower test cost and increasing colorectal cancer care costs.

METHODS

Using a Markov model, we compared faecal DNA testing every 3 years, annual faecal occult blood testing or immunochemical testing, and colonoscopy every 10 years.

RESULTS

In the base case, faecal occult blood testing and faecal immunochemical testing gained life-years/person and cost less than no screening. Faecal DNA testing version 1.1 at $300 (the current PreGen Plus test) gained 5323 life-years/100 000 persons at $16 900/life-year gained and faecal DNA testing version 2 (enhanced test) gained 5795 life-years/100 000 persons at $15 700/life-year gained vs. no screening. In the base case and most sensitivity analyses, faecal occult blood testing and faecal immunochemical testing were preferred to faecal DNA testing. Faecal DNA testing version 2 cost $100 000/life-year gained vs. faecal immunochemical testing when per-cycle adherence with faecal immunochemical testing was 22%. Faecal immunochemical testing with excellent adherence was superior to colonoscopy every 10 years.

CONCLUSIONS

As novel biological therapies increase colorectal cancer treatment costs, faecal occult blood testing and faecal immunochemical testing could become cost-saving. The cost-effectiveness of faecal DNA testing compared with no screening has improved, but faecal occult blood testing and faecal immunochemical testing are preferred to faecal DNA testing when patient adherence is high. Faecal immunochemical testing may be comparable to colonoscopy every 10 years in persons adhering to yearly testing.