Progress report on controlled trial of fecal occult blood testing for the detection of colorectal neoplasia

Guaiac-based faecal occult blood tests versus faecal immunochemical tests for colorectal cancer screening in average-risk individuals

BACKGROUND

Worldwide, many countries have adopted colorectal cancer (CRC) screening programmes, often based on faecal occult blood tests (FOBTs). CRC screening aims to detect advanced neoplasia (AN), which is defined as CRC or advanced adenomas. FOBTs fall into two categories based on detection technique and the detected blood component: qualitative guaiac-based FOBTs (gFOBTs) and faecal immunochemical tests (FITs), which can be qualitative and quantitative. Screening with gFOBTs reduces CRC-related mortality.

OBJECTIVES

To compare the diagnostic test accuracy of gFOBT and FIT screening for detecting advanced colorectal neoplasia in average-risk individuals.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, BIOSIS Citation Index, Science Citation Index Expanded, and Google Scholar. We searched the reference lists and PubMed-related articles of included studies to identify additional studies.

SELECTION CRITERIA

We included prospective and retrospective studies that provided the number of true positives, false positives, false negatives, and true negatives for gFOBTs, FITs, or both, with colonoscopy as reference standard. We excluded case-control studies. We included studies in which all participants underwent both index test and reference standard ("reference standard: all"), and studies in which only participants with a positive index test underwent the reference standard while participants with a negative test were followed for at least one year for development of interval carcinomas ("reference standard: positive"). The target population consisted of asymptomatic, average-risk individuals undergoing CRC screening. The target conditions were CRC and advanced neoplasia (advanced adenomas and CRC combined).

DATA COLLECTION AND ANALYSIS

Two review authors independently screened and selected studies for inclusion. In case of disagreement, a third review author made the final decision. We used the Rutter and Gatsonis hierarchical summary receiver operating characteristic model to explore differences between tests and identify potential sources of heterogeneity, and the bivariate hierarchical model to estimate sensitivity and specificity at common thresholds: 10 µg haemoglobin (Hb)/g faeces and 20 µg Hb/g faeces. We performed indirect comparisons of the accuracy of the two tests and direct comparisons when both index tests were evaluated in the same population.

MAIN RESULTS

We ran the initial search on 25 June 2019, which yielded 63 studies for inclusion. We ran a top-up search on 14 September 2021, which yielded one potentially eligible study, currently awaiting classification. We included a total of 33 "reference standard: all" published articles involving 104,640 participants. Six studies evaluated only gFOBTs, 23 studies evaluated only FITs, and four studies included both gFOBTs and FITs. The cut-off for positivity of FITs varied between 2.4 μg and 50 µg Hb/g faeces. For each Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 domain, we assessed risk of bias as high in less than 20% of studies. The summary curve showed that FITs had a higher discriminative ability than gFOBTs for AN (P < 0.001) and CRC (P = 0.004). For the detection of AN, the summary sensitivity of gFOBTs was 15% (95% confidence interval (CI) 12% to 20%), which was significantly lower than FITs at both 10 μg and 20 μg Hb/g cut-offs with summary sensitivities of 33% (95% CI 27% to 40%; P < 0.001) and 26% (95% CI 21% to 31%, P = 0.002), respectively. Results were simulated in a hypothetical cohort of 10,000 screening participants with 1% CRC prevalence and 10% AN prevalence. Out of 1000 participants with AN, gFOBTs missed 850, while FITs missed 670 (10 μg Hb/g cut-off) and 740 (20 μg Hb/g cut-off). No significant differences in summary specificity for AN detection were found between gFOBTs (94%; 95% CI 92% to 96%), and FITs at 10 μg Hb/g cut-off (93%; 95% CI 90% to 95%) and at 20 μg Hb/g cut-off (97%; 95% CI 95% to 98%). So, among 9000 participants without AN, 540 were offered (unnecessary) colonoscopy with gFOBTs compared to 630 (10 μg Hb/g) and 270 (20 μg Hb/g) with FITs. Similarly, for the detection of CRC, the summary sensitivity of gFOBTs, 39% (95% CI 25% to 55%), was significantly lower than FITs at 10 μg and 20 μg Hb/g cut-offs: 76% (95% CI 57% to 88%: P = 0.001) and 65% (95% CI 46% to 80%; P = 0.035), respectively. So, out of 100 participants with CRC, gFOBTs missed 61, and FITs missed 24 (10 μg Hb/g) and 35 (20 μg Hb/g). No significant differences in summary specificity for CRC were found between gFOBTs (94%; 95% CI 91% to 96%), and FITs at the 10 μg Hb/g cut-off (94%; 95% CI 87% to 97%) and 20 μg Hb/g cut-off (96%; 95% CI 91% to 98%). So, out of 9900 participants without CRC, 594 were offered (unnecessary) colonoscopy with gFOBTs versus 594 (10 μg Hb/g) and 396 (20 μg Hb/g) with FITs. In five studies that compared FITs and gFOBTs in the same population, FITs showed a higher discriminative ability for AN than gFOBTs (P = 0.003). We included a total of 30 "reference standard: positive" studies involving 3,664,934 participants. Of these, eight were gFOBT-only studies, 18 were FIT-only studies, and four studies combined both gFOBTs and FITs. The cut-off for positivity of FITs varied between 5 µg to 250 µg Hb/g faeces. For each QUADAS-2 domain, we assessed risk of bias as high in less than 20% of studies. The summary curve showed that FITs had a higher discriminative ability for detecting CRC than gFOBTs (P < 0.001). The summary sensitivity for CRC of gFOBTs, 59% (95% CI 55% to 64%), was significantly lower than FITs at the 10 μg Hb/g cut-off, 89% (95% CI 80% to 95%; P < 0.001) and the 20 μg Hb/g cut-off, 89% (95% CI 85% to 92%; P < 0.001). So, in the hypothetical cohort with 100 participants with CRC, gFOBTs missed 41, while FITs missed 11 (10 μg Hb/g) and 11 (20 μg Hb/g). The summary specificity of gFOBTs was 98% (95% CI 98% to 99%), which was higher than FITs at both 10 μg and 20 μg Hb/g cut-offs: 94% (95% CI 92% to 95%; P < 0.001) and 95% (95% CI 94% to 96%; P < 0.001), respectively. So, out of 9900 participants without CRC, 198 were offered (unnecessary) colonoscopy with gFOBTs compared to 594 (10 μg Hb/g) and 495 (20 μg Hb/g) with FITs. At a specificity of 90% and 95%, FITs had a higher sensitivity than gFOBTs.

AUTHORS' CONCLUSIONS

FITs are superior to gFOBTs in detecting AN and CRC in average-risk individuals. Specificity of both tests was similar in "reference standard: all" studies, whereas specificity was significantly higher for gFOBTs than FITs in "reference standard: positive" studies. However, at pre-specified specificities, the sensitivity of FITs was significantly higher than gFOBTs.

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

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

Selection Criteria in Colorectal Cancer Screening

The authors report the results of a risk questionnaire (RQ) used in a population-based screening program for colorectal cancer. The positive predictive value (PPV) for cancer or adenoma was evaluated for the Hemoccult test (HO) and for all RQ items (symptoms, personal and familial risk) in 8,114 cases, by univariate and multivariate analysis. A significant correlation with the presence of cancer or adenoma was observed for HO-positive tests, whereas a significant correlation was absent for most RQ variables. The use of an RQ in screening practice is disregarded since it does not improve the rate of cancer detection. Moreover, the increase in the detection rate of HO-negative adenomas does not justify the high rate (0.18) of screening responders selected for endoscopic diagnostic workup, a figure which influences negatively the overall compliance to screening.

Role of faecal occult bloods in the diagnosis of iron deficiency anaemia

OBJECTIVE

To determine whether faecal occult blood (FOB) testing in patients with iron deficiency anaemia (IDA) can predict the presence of gastrointestinal cancer.

DESIGN

Cohort study.

SETTINGS

Single secondary care hospital UK.

PATIENTS

All individuals aged 20 years and older referred for the investigation for IDA.

INTERVENTIONS

Data was collected from all the patients regarding haemoglobin (Hb), mean corpuscular volume, age, sex, symptomatology and medication. All patients had FOB tests using laboratory guaiac and haemocell methods, and then underwent gastroscopy and colonoscopy.

MAIN OUTCOME MEASURES

Accuracy, sensitivity and specificity of FOBs for identifying cancer in the upper or lower gastrointestinal tract.

RESULTS

In total, 292 patients completed the study; 37 patients were diagnosed with carcinoma (colon 34, gastro-oesophageal 3). Using an optimal combination of lab guiaic and haemocell test resulted in just one colorectal cancer being missed, a sensitivity of 97%, specificity of 49% and negative predictive value of 99%. The test was less effective for upper gastrointestinal cancer, with 2/3 tumours missed by the tests.

CONCLUSIONS

Patients who have negative FOB tests are very unlikely to have a colorectal cancer, and the benefits to further colonic investigation is limited. This should be carefully considered in patients with significant comorbidities, where the risks of investigation may outweigh the benefits.

Effective screening for bowel cancer: a United kingdom perspective

Bowel cancer is a major cause of morbidity and death and is a high cost to health care systems. Screening currently offers the best chance of improving outcomes from bowel cancer. When introducing screening, the problems encountered in other cancers need to be avoided to maximize benefits and minimize harms.

Survey of primary physicians' knowledge of colorectal cancer screening

OBJECTIVE

Colorectal cancer (CRC) is the most common of the gastrointestinal cancers in Israel. The low rate of patient compliance to a recent CRC screening program of Clalit Health Services, a major health management organization in Israel, prompted the present survey of primary care physicians' knowledge and practices regarding CRC screening.

METHODS

A 23-item questionnaire, formulated according to the policy of the Israel Ministry of Health and the recommendations of the American Gastroenterological Association, was distributed to 150 primary physicians of Clalit Health Services. The relative ratio of correct to incorrect answers was calculated for every question and by professional group.

RESULTS

The response rate was 89%. Total score (out of a maximum 23) was 20.68 for family physicians (experts in family medicine), 17.79 for experts in other fields, and 17.82 for general practitioners (average, 0.90, 0.77, and 0.77, respectively). The score for the family physicians was significantly higher than for the other two groups (P=0.0070). Clustering items by specific issues yielded significantly better scores for the family physicians in four areas: screening (P=0.0164), appropriate test for high-risk population in Israel (P=0.0012), definition of average-risk population (P=0.0012), and CRC symptoms (P=0.0108). A low level of knowledge on the definition of the high-risk population was noted in all three groups.

CONCLUSIONS

Experts in family medicine in Israel have significantly greater knowledge of most issues of CRC than primary care experts in other fields and general practitioners, although all three groups lack knowledge on the definition of the high-risk population. Continuing physician education should focus on these areas.

Survey of surgeons' and internists' knowledge of colorectal cancer screening

BACKGROUND

Colorectal cancer (CRC) is the most common of the gastrointestinal cancers in Israel, with an incidence of 50 cases per 100,000 for men and 45 per 100,000 for women in 2000.

AIM

The low rate of patient compliance noted in CRC screening program conducted in our center, prompted the present survey of the knowledge and practices regarding CRC screening recommendations.

METHODS

A 23-item questionnaire formulated according to the Israeli Ministry of Health policy and recommendation of the American Gastroenterological Association was distributed among the physicians of the six departments of internal medicine, and the department of surgery of the Rabin Medical Center. The relative ratio of correct answers was calculated for every question and by subgroups: internists and surgeons, experts and residents in internal medicine and in surgery.

RESULTS

Fifty-five of 80 physicians (69%) completed the questionnaire. The total score for all participants was 15.82 (average 0.68), significantly lower than the optimal correct score of 23 (average 1.00). The internists had a similar total score to the surgeons, 15.61 and 15.28. When the questions were clustered according to specific issues and only the correct answers for each cluster scored, the success rate decreased with a range of 19-69%. Only 22% of responders did not advise fecal occult blood test (FOBT) for the high-risk population; 57% thought the screening age range was 40-65 years, and only 37% knew that the high-risk criteria include a family history of ovarian cancer.

CONCLUSION

Both internists and surgeons' knowledge about screening recommendations of CRC can be improved. Health authorities should invest greater efforts in continuing physician education. We believe that this strategy will increase the participation rate in CRC preventive programs.

Impact of a physician-oriented intervention on follow-up in colorectal cancer screening

BACKGROUND

Complete diagnostic evaluation or CDE (i.e., colonoscopy or combined flexible sigmoidoscopy plus barium enema X-ray) is often not performed for persons with an abnormal screening fecal occult blood test (FOBT+) result.

METHOD

This study evaluated the impact of a reminder-feedback and educational outreach intervention on primary care practice CDE recommendation and performance rates. Four hundred seventy primary care physicians (PCPs) in 318 practices participated in the study. Patients were mailed an FOBT kit annually as part of a screening program. Practices were randomly assigned to a Control Group (N = 198) or an Intervention Group (N = 120). During an 18-month pre-randomization period and a 9-month post-randomization period, 2992 screening FOBT+ patients were identified. Intervention practices received the screening program and the intervention. Control practices received only the screening program. Study outcomes were baseline-adjusted CDE recommendation and performance rates.

RESULTS

At baseline, about two-thirds of FOBT+ patients received a CDE recommendation, and about half had a CDE performed. At endpoint, CDE recommendation and performance rates were both significantly higher for the Intervention as compared to the Control practices (OR = 2.28; 95% CI: 1.37, 3.78, and OR = 1.63; 95% CI: 1.06, 2.50, respectively).

CONCLUSIONS

The reminder-feedback plus educational outreach intervention significantly increased CDE recommendation and performance.

Screening the average risk population for colorectal cancer: the Israeli experience 1985-97

INTRODUCTION

Five prospective, controlled trials of CRC screening, 4 of them randomized, using the Hemoccult test in large populations, have been reported from Europe and USA. In all the series stage shifting was documented, and mortality from CRC was reduced by 12-33%. In comparison with this large experience, the Israeli screening programs in the average risk population are very modest, started as case findings and expanded to nation-wide recommendation for FOBT in 1999. In this study the Israeli experience between 1985 and 1997 was documented.

METHODS

Medline search of the last 22 years for screening programs in Israel was performed, as well as personal contact with all the Israeli investigators. Reports to the Israeli Cancer Association (ICA) were collected, reviewed and summarized.

RESULTS

Since 1985 8 papers about faecal occult blood test (FOBT) and 5 papers about flexible sigmoidoscopy (SIG) screening in average risk population have been published. 35 685 people have been screened, 110 cases of CRC and 546 cases of adenoma were found. The yield of SIG was 4 times that of FOBT for CRC. In addition, since 1990 80 084 people were screened according to the reports to the ICA. Five hundred and six cases of CRC and 2714 cases of adenoma were found. In the only prospective, controlled study, CRC incidence and mortality were significantly decreased in participants of a FOBT screening program, an effect lasting 11 years. Refusers were more likely to be male, of Asian-African decent, smokers, and consumers of more coffee and less tea or dairy food.

CONCLUSION

FOBT may protect against CRC for prolonged periods. Individuals who refuse FOBT have significantly higher CRC incidence and mortality rates than those who accept testing. The Israeli experience, thus small, supports a comprehensive screening campaign for early detection of CRC in Israel.

Case-control study of screening colonoscopy in relatives of patients with colorectal cancer

OBJECTIVES

The efficacy of colonoscopic screening and polypectomy for the prevention of colorectal cancer (CRC) is well accepted but has never been documented in a prospective, controlled study. Screening by sigmoidoscopy has been found to reduce mortality from cancer of the rectum and distal colon. Case-control studies provide an alternative method for determining the efficacy of screening methods.

METHODS

Between 1998 and 2000, a total of 40 subjects were found to have CRC (study group) and 160 had a normal colon (control group) among asymptomatic individuals participating in a screening colonoscopy program for a high-risk population of first-degree relatives of CRC patients. We compared these groups for screening by fecal occult blood testing, flexible sigmoidoscopy, barium enema, and colonoscopy in the 10-yr period before the index colonoscopy.

RESULTS

Screening colonoscopy was performed in only 2.5% of the case subjects and 48.7% of controls (p < 0.0001), and all screening procedures in 12.5% and 73.7%, respectively (p < 0.0001). A statistically significant difference was also found for screening with fecal occult blood test, but not for flexible sigmoidoscopy or barium enema. Significant adenomatous polyps >1 cm in diameter were detected and removed in 19% of the control group within 10 yr of the index colonoscopy. Six (15%) of the patients in the study group died of CRC.

CONCLUSIONS

Screening by colonoscopy can prevent progression to CRC from adenomatous polyps and may reduce the mortality associated with this devastating disease.

Complete diagnostic evaluation in colorectal cancer screening: research design and baseline findings

BACKGROUND

While indicated by guidelines, complete diagnostic evaluation, or CDE (i.e., colonoscopy or combined flexible sigmoidoscopy plus barium enema X ray), is often not recommended and performed for persons with an abnormal screening fecal occult blood test (FOBT) result. We initiated a randomized trial to assess the impact of a physician-oriented intervention on CDE rates in primary care practices.

METHODS

In 1998, we identified 1,184 primary care physicians (PCPs) in 584 practices whose patients received FOBTs that are mailed annually by a managed care organization screening program. A total of 470 PCPs in 318 practices completed a baseline survey. Practices were randomly assigned either to a Control Group (N = 198) or to an Intervention Group (N = 120). Control Group practices received the screening program. Intervention Group practices received the screening program and the intervention (i.e., CDE reminder-feedback plus educational outreach). Practice CDE recommendation and performance rates are the primary outcomes to be measured in the study.

RESULTS

Baseline CDE recommendation and performance rates were low and were comparable in Control and Intervention Group practices (54 to 57% and 39 to 40%, respectively). PCPs in the practices tended to view FOBT screening and CDE favorably, but had concerns about screening efficacy, time involved in CDE, and patient discomfort and adherence. Control Group physicians were more likely than Intervention Group physicians to believe that a mail-out FOBT screening program helps in the practice of medicine.

CONCLUSIONS

We were able to enroll a high proportion of targeted primary care practices, measure practice characteristics and CDE rates at baseline, and develop and implement the intervention. Study outcome analyses will take into account baseline differences in practice characteristics.

Design of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial

The objectives of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial are to determine in screenees ages 55-74 at entry whether screening with flexible sigmoidoscopy (60-cm sigmoidoscope) can reduce mortality from colorectal cancer, whether screening with chest X-ray can reduce mortality from lung cancer, whether screening men with digital rectal examination (DRE) plus serum prostate-specific antigen (PSA) can reduce mortality from prostate cancer, and whether screening women with CA125 and transvaginal ultrasound (TVU) can reduce mortality from ovarian cancer. Secondary objectives are to assess screening variables other than mortality for each of the interventions including sensitivity, specificity, and positive predictive value; to assess incidence, stage, and survival of cancer cases; and to investigate biologic and/or prognostic characterizations of tumor tissue and biochemical products as intermediate endpoints. The design is a multicenter, two-armed, randomized trial with 37,000 females and 37,000 males in each of the two arms. In the intervention arm, the PSA and CA125 tests are performed at entry, then annually for 5 years. The DRE, TVU, and chest X-ray exams are performed at entry and then annually for 3 years. Sigmoidoscopy is performed at entry and then at the 5-year point. Participants in the control arm follow their usual medical care practices. Participants will be followed for at least 13 years from randomization to ascertain all cancers of the prostate, lung, colorectum, and ovary, as well as deaths from all causes. A pilot phase was undertaken to assess the randomization, screening, and data collection procedures of the trial and to estimate design parameters such as compliance and contamination levels. This paper describes eligibility, consent, and other design features of the trial, randomization and screening procedures, and an outline of the follow-up procedures. Sample-size calculations are reported, and a data analysis plan is presented.

Early detection for colorectal cancer: new aspects in fecal occult blood screening

The authors report on promising diagnostic methods of occult intestinal bleeding and discusses the potential new strategy of early detection of colorectal carcinomas in respect to old and new diagnostic measures available. Because of the limited sensitivity and specificity of classical methods used for the demonstration of occult fecal blood, the authors recommend the introduction of new techniques and markers in screening practice. It is presumed that new discoveries in molecular biology will improve the accuracy of early colorectal cancer prevention. Their implementation into routine screening, however, will not take place in the near future. Until their realization, improved screening efficacy is expected from the use of more specific and sensitive blood tests.

Molecular screening for colon cancer detection

Screening for colorectal cancer is a widely debated issue. Faecal occult blood testing is, at present, the only single test available which is applicable to large populations. However, progress in the definition of genetic alterations in the aetiopathogenesis both of sporadic and hereditary colorectal cancer have made it possible to set up molecular methods for identifying subjects with colorectal cancer or who are at risk of developing it. The target genes involved and the source of genomic material to be studied are different for sporadic and hereditary conditions and determine the type of test to use.

Colorectal cancer

Colorectal cancer is a leading cause of morbidity and mortality with about 300,000 new cases and 200,000 deaths in Europe and the USA each year. Published trials have established a role for chemotherapy in colorectal cancer, in the adjuvant setting for Dukes C colon cancer, with an absolute survival benefit of about 5% and in advanced colorectal cancer, for which it improves quality of life and increases survival by 6-12 months. For rectal cancer, radiotherapy decreases rates of local recurrence and, in locally advanced disease, successfully palliates pain, tenesmus, and bleeding. The evolving understanding of colorectal carcinogenesis, in particular recognition of vital genes that may be mutated or lost during tumour development, has been translated into innovative gene therapy techniques. Finally it is increasingly apparent that surgical site specialisation and a multidisciplinary approach (including surgeons, pathologists, and oncologists) may lead to optimum outcomes for patients with colorectal cancer.

Predictors of fecal occult blood screening among older socioeconomically disadvantaged Americans: a replication study

Socioeconomically disadvantaged elderly are less likely to participate in fecal occult blood testing (FOBT). A quasi-experimental design was used in this operational replication study to determine predictors at baseline of subsequent participation in FOBT. Sixty-five percent of the 211 participants in the replication study participated in FOBT, and 47% of the 171 participants in the original study participated in FOBT. Predictors for FOBT in the replication study were male gender, age of 65-75 years old, ability to go places without assistance, history of having had a digital rectal examination and FOBT. This replication study supports targeting socioeconomically disadvantaged populations for FOBT as well as females, persons 85 years and older, persons who need assistance in travel, and person who have not had FOBT before. The results show that socioeconomically disadvantaged persons will participate in FOBT when effective educational interventions that include adaptation for aging changes are used.

Fecal alpha 1-antitrypsin detection of colorectal neoplasia. An evaluation using HemoQuant

Fecal alpha 1-antitrypsin measurement may be of value for the detection of colorectal neoplasia and is compared with the HemoQuant test in 119 subjects with either a screen-positive Hemoccult result (N = 78) or iron-deficiency anaemia (N = 41). Nineteen patients were found to have colorectal cancer, 35 had colorectal adenomatous polyps, 5 had inflammatory bowel disease, and 60 had no detected cause of occult blood loss. Of the cancer patients, 63% (12/19) were detected by fecal alpha 1-antitrypsin and 63% (12/19) by HemoQuant. Of the adenomas > 1 cm in diameter 33% (7/23) were detected by fecal alpha 1-antitrypsin and 26% (6/23) by HemoQuant. There was a poor correlation between fecal alpha 1-antitrypsin and HemoQuant results for colorectal cancers (r = 0.37, P > 0.05), and combining the tests, the sensitivity for colorectal cancer was increased to 84% (16/19). Fecal protein loss, as measured using alpha 1-antitrypsin, appears to involve largely different mechanisms from that of blood loss from colorectal cancers.

Determinants of persistent compliance with screening for colorectal cancer

Mass population screening for colorectal cancer is currently being evaluated by means of randomized controlled trials. These trials point to the likelihood that, if implemented, the level of both initial and sustained compliance will prevent the full potential of screening being realised. The paper opens by reviewing the evidence on determinants of compliance, both initial and longer term, although little empirical evidence on adherence to repeated screening is currently available. The paper then presents the results of a survey of persistent compliers and non-compliers within the English screening trial, in order to identify those characteristics most closely associated with persistent compliance behaviour. Persistent compliers are found, inter alia, to be of higher socio-economic classes than persistent non-compliers, to have more personal and family experiences of illness and to visit their dentists more regularly. The results suggest that generalized attempts at compliance enhancement would be ineffectual against the prevailing background characteristics of the non-compliant population, and that the more overt targeting of efforts in this respect is to be preferred.

A case-control study to evaluate efficacy of screening for faecal occult blood

OBJECTIVES

Faecal occult blood testing is routinely used for early detection of colorectal cancer, but evidence of its efficacy in preventing death from colorectal cancer is limited. A case-control study was carried out to evaluate whether screening for faecal occult blood is associated with a reduced risk of fatal colorectal cancer.

SETTING

A health maintenance organisation in western Washington State, which has offered its members faecal occult blood testing every two years since 1983.

METHODS

Cases (n = 248) were members of the health maintenance organisation who died from colorectal cancer between 1986 and 1991. For each case, two control subjects, who did not die from colorectal cancer and who were similar to each case in age, gender, and year of enrollment at the health maintenance organisation, were randomly selected from the membership list of the year in which the case was diagnosed (n = 496). Information about episodes of faecal occult blood testing (including the location and reason for the test, and the evaluation of positive tests) and potential confounders was obtained from medical records.

RESULTS

Cases were less likely than controls to have ever been screened (odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.5 to 1.0), consistent with a beneficial impact of screening. There was little difference, however, for screening that had taken place within a three year period before diagnosis (OR = 0.9, 95% CI 0.6 to 1.2), the maximum interval during which most tumours ought to have been detectable by faecal occult blood testing. A reduction in risk was seen for home testing but not for office testing, and in individuals aged less than 75 but not in those aged 75 or older. Although most of the 21 controls with a positive faecal occult blood test underwent some additional testing, only five (24%) were evaluated with colonoscopy or air contrast barium enema.

CONCLUSIONS

While there can be uncertainty as to whether specific faecal occult blood tests were performed as screening or diagnostic tests, those performed at home and in younger persons may be relatively less likely to be diagnostic tests that were misclassified as screening. Thus the modest reduced risk associated with faecal occult blood testing in these settings/persons may reflect genuine benefit. However, the presence of a reduced risk associated with a screening faecal occult blood test received in the past, well before a tumour or polyp might bleed enough to allow detection, is compatible with uncontrolled confounding. Interpretation is further complicated by the fact that a number of individuals in the study group who had positive test results underwent limited or no diagnostic testing. Thus our results should be interpreted with considerable caution.

Endoscopic and histologic correlates of colorectal polyp bleeding

Until now, the exact mechanism of bleeding from colorectal polyps has not been demonstrated. The present study aimed to identify macroscopic factors and the main source of polyp bleeding. One hundred fifty-seven cases of single colorectal polyp from a variety of clinical situations were investigated to determine whether surface area, shape, color, and location in the colon were correlated with a positive result in the fecal occult blood test. We also searched for the site of bleeding on the surface of polyps under a dissecting microscope and investigated the relationship between bleeding and microerosion and thin surface epithelium on the maximal vertical cross-section of the polyp. The presence of fecal occult blood was found to be correlated with the surface area of colonic polyps. We demonstrated that a red color tone of polyps was caused largely by microerosion and that the area of both microerosion and thin surface epithelium was significantly larger on polyps associated with a positive fecal occult blood test result. The extent of microerosion and thin surface epithelium was found to be correlated with the polyp surface area and villous component. These observations strongly suggest that the area of microerosion and thin surface epithelium tends to increase as the surface area expands, resulting in a higher rate of detection of polyps with malignant potential by the fecal occult blood test.

Screening for colorectal cancer

In the past few years, knowledge of the clinical, biologic, and molecular genetic characteristics of colorectal cancer has greatly increased. Although the most cost-effective approach remains to be identified, screening for colorectal cancer can decrease mortality due to this disease by detecting cancers at earlier stages and allowing the removal of adenomas, thus preventing the subsequent development of cancer. Molecular studies that have helped define the genetic basis for this disease hold great promise for the development of better and more powerful methods to identify populations at risk. Individually, these technological, clinical, and basic-science advances are exciting; together, they promise to move us closer to the goal of substantially reducing mortality due to colorectal cancer.

Screening for colorectal cancer: reasons for refusal of faecal occult blood testing in a general practice in England

STUDY OBJECTIVE

To ascertain reasons for non-compliance with faecal occult blood tests in colorectal cancer screening programmes.

DESIGN

A standard interview by a trained nurse of a random sample of those who declined screening.

SETTING

The Leicestershire town of Market Harborough, where most of the 25,000 population are served by a single general practice of 10 partners.

PARTICIPANTS

Altogether 4185 residents aged 51 to 70 years were invited to receive a free faecal occult blood test (Haemoccult). Eighty one subjects from a sample of 351 who wrote declining the offer were interviewed.

MAIN RESULTS

Non-compliers were divided into those who did not request a test kit and those who returned an unused kit. In the former group the commonest reasons given were intercurrent illness (39%), fear of further tests and surgery (24%), and feeling well (22%). For those who returned unused kits the commonest reasons were the unpleasantness of the stool collection procedure (65%), feeling well (30%), intercurrent illness (23%), and fear of further tests and surgery (20%). In both groups the main concern of those who did not comply were fear of further diagnostic tests and surgery rather than concern at the lack of effective treatment for cancer.

CONCLUSIONS

To increase compliance, education and publicity must explain the concept of asymptomatic illness and allay people's fear of hospital investigation and treatment. The benefits of screening should be particularly emphasised to those who return kits so they may overcome their reservations.

Cost-effectiveness analysis of strategies for colorectal cancer screening in Japan

To determine the cost-effectiveness of colorectal cancer screening strategies in Japan and to determine the influence of long-term compliance with screening programs on the selection of strategies, the natural history of a simulated cohort of 40-year-old Japanese of both genders was modeled with and without colorectal cancer screening until age 75 years. Survival, number of complications, and direct medical costs were compared among several combinations of screening examinations. In addition, the age of initiating screening was varied, as was the long-term compliance rate. Strategies using immunological fecal occult blood test were found to be the most cost-effective. Immunological fecal occult blood test followed by colonoscopy, if positive, would save 24.05 (5.88 discounted) days of life and cost 28,420 yen (US $210) per screened person, thus offering a cost-effectiveness ratio of 1.765 million yen (US $13,100) per year of life saved. If long-term compliance is 100%, initiating screening at age 40 years offers more years of life saved and a low incremental cost of screening. However, if more likely dropout rates are considered, initiation at age 40 years is dominated by later initiation of screening.

Faecal occult blood screening for colorectal neoplasia in a targeted high-risk population

A general practice-based programme was initiated in 1987 to identify individuals at high risk of developing large bowel cancer and offer them screening of faecal occult blood. In all, 5298 people from 21 general practices in the Guildford area were offered 7510 screening tests. In total, 5934 tests were completed (compliance rate 79.0 per cent) with 287 positive results (4.8 per cent). Of the patients with positive results, 44 had cancer and 38 polyps. The sensitivity of the test for cancer was 63 per cent, the specificity 96 per cent and the positive predictive value for all neoplasia 29 per cent. The detection rate of 44 cancers per 5934 people screened compares favourably with data from the Nottingham-based screening of an unselected population (0.74 versus 0.23 per cent).

Screening strategies for colorectal cancer

The efficacy of screening for colorectal cancer has not been established. Policy-making organizations differ in recommendations for asymptomatic and high-risk groups because of the inadequacy of current evidence. A critical appraisal of the current evidence for screening for colorectal cancer and a discussion of the aims and pitfalls of screening programs are presented.

Detection of colorectal cancer by faecal alpha 1-antitrypsin

Alpha 1-antitrypsin was measured in 5-day faecal collections from patients with colorectal cancer or adenomatous polyps and a symptomatic control group. Collections were homogenized and lyophilized prior to measurement of alpha 1-antitrypsin by radial immuno-diffusion. Colorectal cancer dry weight concentrations were significantly higher than the symptomatic control results, with 57% having results greater than 95% normal values of this control group. There was no significant difference between adenomatous polyp dry weight concentrations and symptomatic control results. Wet weight concentrations were calculated from wet/dry ratios. Colorectal cancer wet weight concentrations were significantly higher than symptomatic control results with 48% having results greater than 95% normal values of this control group. Alpha 1-antitrypsin was also measured in non-lyophilized samples from an asymptomatic control group (n = 39). Colorectal cancer wet weight concentrations were significantly higher than asymptomatic control results, with 62% having results greater than 95% normal values of this control group. Faecal alpha 1-antitrypsin measurement deserves further assessment for use in detecting colorectal cancer.

Colorectal carcinoma: analysis of management in two medical eras

Trends in presentation, diagnosis, management, and outcome were analyzed for 503 patients with colorectal cancer seen at the UCLA Medical Center between 1960 and 1970 (Group A; n = 210) and 1980 and 1985 (Group B; n = 293). Patients in the latter group exhibited a shift in site to the right side of the colon (18% in Group A vs. 31% in Group B; P < .01), an increase in the number of primary resections without colostomy (38% vs. 61%; P < .01), a lower overall complication rate (28% vs. 18%; P = .01), and a decline in 30-day mortality (6.2% vs. 2%; P = .01). Although little difference was seen in detection of asymptomatic tumors, earlier lesions were treated in the latter group, accounting for substantially reduced rate of recurrence (69% in Group A vs. 44% in Group B; P < .01). Future management should include an emphasis on earlier detection in order to continue the trend toward enhanced survival.

Cancer presentation in the emergency department: a failure of primary care

Emergency departments are intended to be the location of entry into the health care system for patients with acute problems, such as injuries and myocardial infarctions. In contrast, cancer should optimally be detected during periodic health examinations, either through screening procedures or by early detection from signs and symptoms which prompt a routine visit to a primary care physician. This study was undertaken to describe patients who present to an emergency department with urgent symptoms and signs, are hospitalized, and subsequently diagnosed with cancer (ED group). One hundred twenty-nine patients were retrospectively studied. When compared with patients diagnosed in a primary care setting (tumor registry patients), the ED group was significantly older, more often male, had a significantly lower survival rate, and more frequent metastatic disease at diagnosis (P less than .001). The ED group accounted for 5.3% of the new tumor registry patients for the study years. Only 3.1% of the ED group had no insurance, and 21% reported no personal physician. Strategies are needed for patients and physicians to reduce the number of late-diagnosed cancer cases presenting in emergency departments.

Screening for large bowel neoplasms in individuals with a family history of colorectal cancer

Logistical problems associated with population screening for colorectal cancer are identified and the possibility of targeting screening to those with a familial predisposition to the disease is discussed. Evidence for a substantial genetic effect on the overall incidence of colorectal cancer is reviewed. The screening detection rate of colorectal neoplasms in relatives of patients with colorectal cancer has been shown to be higher than that expected in a non-selected population; the evidence that polypectomy will reduce future colorectal cancer risk in such individuals is explored. Recent advances in the molecular genetics of colorectal cancer susceptibility are reviewed; it is possible that a genetic test might be developed in the future which could identify at least a proportion of those at risk. Excluding financial considerations, the risk-benefit ratio of colonoscopy in a screened population is intimately related to the remaining risk of colorectal cancer in those who undergo the examination. At present, patients undergoing colonoscopy to investigate a positive faecal occult blood (FOB) test as part of a population-based screening programme include individuals with a familial predisposition as well as those without. About 20 per cent of all cases of colorectal cancer are associated with an obvious genetic predisposition, and the risk of cancer in their relatives is high. Because false positives occur with Haemoccult, the residual risk to the population who are FOB positive but do not have a familial trait may be sufficiently low that the dangers of colonoscopy could outweigh the potential benefits. Scotland has a high incidence of colorectal cancer, and analysis of recent Scottish incidence data shows an actuarial lifetime risk of developing this disease of one in 23 for men and one in 33 for women. As a family history of the disease increases that risk by two to four times and the neoplasms arise throughout the colon in such a group, there may be a case for offering colonoscopy to all first-degree relatives of those under 50 years of age at diagnosis, if not of all index cases of colorectal cancer.

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

OBJECTIVE

To compare the readability and sensitivity of a new guaiac faecal occult blood test, HemoccultSENSA, with those of a standard guaiac-based test, Hemoccult, in a normal working environment.

DESIGN

The two tests were performed in parallel on routine clinical and contrived faecal specimens; those developing the tests were blinded as to the test type.

SETTING

All tests were carried out in the hospital ward environment under normal conditions by nurses working in the ward.

SAMPLES

Fifty faecal samples from healthy volunteer subjects (low concentrations of haemoglobin were added to 40 of these samples) and 145 faecal samples from 65 inpatients likely to have gastrointestinal bleeding.

MAIN OUTCOME MEASURES

Test positivity rate, and graded measures of colour intensity, colour stability and colour pattern.

RESULTS

With patients' samples, the new test gave a greater number of positive results than the standard test (73.1% v. 65.5%; 95% confidence interval of the difference, 3.3%-11.9%). With contrived samples, the blue colour produced during development was more intense (P less than 0.0003), more stable (P less than 0.0025) and covered a larger area (P less than 0.01) with the new test compared with the standard test.

CONCLUSIONS

These results demonstrate the better readability and slightly higher sensitivity of the new test. They justify its use in the ward environment or doctor's office. Patients being tested should consume a low peroxidase diet until the specificity of the new test has been fully evaluated.

The utilization of fecal occult blood testing in the institutionalized elderly

OBJECTIVE

To examine physician use of stool guaiac testing in order to determine indications for testing, how the test was used, and the consequences of a particular test result.

DESIGN

Retrospective case series.

SETTING

Large midwestern inpatient nursing home facility.

PATIENTS

All patients with positive fecal occult blood tests (FOBT) and one-third of patients with negative FOBT.

RESULTS

In an 18-month period, 916 occult blood tests were performed on 339 patients (37% of the nursing home census). Patients over age 90 were as likely to receive FOBT as those under age 70. Fourteen percent of those tested had at least one positive test. Fifty-eight percent of the patients with positive tests underwent no additional diagnostic testing. No cause for the positive FOBT was found for 68% of patients receiving the test for routine screening. Physician estimates of how frequently they employed FOBT for these patients correlated very poorly with their actual practices (r = .17).

CONCLUSION

There is a high prevalence of positive results from FOBT among nursing home patients. In most cases, such results do not cause a change of therapy or result in additional workup. Lack of information on the role of FOBT in nursing home patients contributes to the great diversity in utilization of this test by nursing home physicians.

Single-visit screening and treatment of first-degree relatives. Colon cancer pilot study

A pilot study has been carried out to evaluate three aspects of screening of first-degree relatives of patients with colon cancer in four Hamilton hospitals; yield of adenomas, feasibility of a one-visit approach to screening and treatment, and compliance. Protocol included flexible sigmoidoscopy after full bowel preparation, followed immediately by either therapeutic colonoscopy or diagnostic barium enema, depending on the flexible sigmoidoscopy findings. We found adenomas in 19 percent of 88 first-degree relatives, with a mean age of 52, compared with an expectation of 8 percent. The protocol was found to be acceptable to the relatives and workable for the various groups of physicians in three of four hospitals, despite many initial logistic difficulties. Numerous problems were encountered with compliance of referring physicians, index patients, relatives, and investigating physicians.

Assessment of screening for cancer

Screening has a relevant role in and is likely to become an increasingly important instrument for cancer control in the near future. This overview summarizes some of the available evidence on the issue. Some of the opinions are well established. The apparent absence of consensus on other issues should be critically evaluated, too, because the evidence on some procedures is substantially more convincing than that on others. High costs, low compliance, poor curability, and substantial false positive rates, in a disease as relatively rare as cancer, often counterbalance in practice the theoretical benefits of diagnostic anticipation. In screening as well as in treatment for cancer, it is unlikely that major technical breakthroughs will occur in the near future. The evaluation of whether the benefits likely to be achieved by the screening program outweigh its disadvantages by a sufficient margin, therefore, should rely on large and carefully planned controlled studies.

Mass screening for rectal neoplasm in Jiashan County, China

Jiashan county is a rural area in China with very high incidence and mortality rates of colorectal cancer. From 1980 to 1984, we conducted a mass screening for rectal neoplasm in the 11 people's communes in this county. Of the 72,879 individuals who were eligible for screening, 60,496 participated, representing an overall participation rate of 83.0%. Both the fecal occult blood (OB) test and rectoscopy were performed on 47,560 of the participants, and rectoscopy only was performed on the remaining 12,936 individuals. From the mass screening, 15 rectal cancers, 3 carcinoids, 899 polyps, 98 ulcers, and 7 inflammatory tumors were detected, a total of 1022 cases. Eight of the 15 detected cases of rectal cancer were in Dukes' stage A. We did not find any evidence for an association between schistosomiasis and colorectal cancer. Results from the OB test were found to have a negative correlation with results from rectoscopy (odds ratio = 0.8, 95% CI = 0.6, 1.1). The OB test had a high false positive rate of 32.7%, and a poor positive predictive value of 3.5%. Both its positive and negative predictive powers were below 1.0, in other words, its positive likelihood ratio was below 1.0 and negative likelihood ratio was above 1.0, indicating that the OB test is not informative and has a poor predictive accuracy for rectal neoplasm. In addition, there were a number of practical problems concerning the use of the OB test for mass screening in the rural community.(ABSTRACT TRUNCATED AT 250 WORDS)

A critical analysis of the largest reported mass fecal occult blood screening program in the United States

Fecal occult blood testing for the detection of colon cancer remains controversial. We performed a mass screening program from January 24, 1988, to February 19, 1988, with intensive media promotion, including 121 minutes of televised air time. A total of 5,000 primary practitioners were notified by mail. Hemoccult-II tests were distributed to 156,000 individuals; 55,051 (35%) were returned. Ninety-five percent of the respondents were informed of the program by television. A total of 3,375 persons (6%) tested positive for fecal occult blood; of these, 2,469 (73%) informed the center that they saw their physician to initiate a work-up. Information from physicians regarding work-ups was returned on only 1,356 (55%) patients. Diagnostic tests numbered 2,227 (1.6 tests per patient). However, 5% had no testing, 16% had a repeat Hemoccult only, and 35% had neither a barium enema nor colonoscopy performed. Thirty-six colorectal cancers and 212 polyps were identified. The predictive value (i.e., number of cancers per number of patients who tested positive) increased directly by decade. Thirty-three of 36 patients (92%) with cancer underwent either a barium enema or colonoscopy versus only 185 of 438 (42%) patients with a "negative" work-up. Cancers found were carcinoma in situ in 10 patients (29%), Dukes A in 12 (35%), Dukes B in 4 (12%), and Dukes C in 8 (24%); distant metastases were not found in any participant. Thirty-six percent of the tumors were located in either the right or transverse colon. We conclude that: (1) Screening identified early cancers. All were potentially curable and 64% were limited to the bowel wall. (2) Massive Hemoccult distribution was possible over a short interval, but patient and physician compliance was disturbingly low. (3) Total colonic evaluation is mandatory, since at least 36% of tumors were beyond the reach of the flexible sigmoidoscope. (4) Many work-ups were unnecessary (repeat Hemoccults) or inadequate, indicating a need for physician education.

Value of retesting subjects with a positive Hemoccult in screening for colorectal cancer

Within a prospective randomized screening study for early detection of colorectal cancer with rehydrated Hemoccult II test, the possibility of increasing the specificity of the test by retesting patients with an initially positive Hemoccult II test was investigated. Of those offered the test 3561 (62.6 per cent) returned it and it was positive in 210 cases (5.9 per cent). The repeat test was performed by 184 patients and was positive in 68 (1.9 per cent). All those with a positive initial test had rectosigmoidoscopy to 60 cm and a double contrast enema. A carcinoma was found in one in seven patients with a positive retest but in only one in 100 patients with a negative retest (P less than 0.001). The specificity of the test was, therefore, increased from 95 per cent to 98 per cent and the sensitivity was unchanged. Rescreening was offered at a later date and increased numbers were available: 7147 patients returned the test and 369 (5.2 per cent) were positive. The test was repeated in 360 patients and 118 (1.7 per cent) were positive. A colorectal neoplasm was found in one in three of those with a positive repeat test, compared with one in seven of those with a negative repeat test. In conclusion, screening for early detection of colorectal cancer with a rehydrated Hemoccult II test may be followed by investigation of only those patients with a positive retest. Such a procedure will reduce the work-load by 60 per cent without reducing sensitivity.

Adherence to colorectal cancer screening in an HMO population

This study aimed to determine factors that influence fecal occult blood test performance in colorectal cancer screening. A random sample was selected of men and women ages 50 to 74 years of age who had been mailed a fecal occult blood testing kit in a screening program in fall 1986. One year after initial test mailing, sample group members (n = 504) were surveyed by telephone. Four months later, the survey sample received a second fecal occult blood test mailing. Multivariable analysis for subjects with validated past fecal occult blood test status (n = 322) revealed the past testing was positively associated with physician encouragement of screening, age, the belief that cancer is curable, perceived test efficacy, and strong intention to do testing. It also was discovered that persons who felt that they had little control over their health were more likely to have done past testing. Preliminary analysis of prospective adherence showed that the strongest statistically significant independent predictor was past test performance. Prospective adherence among past nontesters (n = 121) was associated with expressed commitment to do fecal occult blood testing and reported presence of colorectal cancer risk factors. Analysis of adherence among past testers (n = 201) revealed that belief in colorectal cancer curability and age were significant predictors. The findings reported here indicate that factors influencing adherence among past nontesters differ from those for past testers. Overall, these results suggest that to increase participation in colorectal cancer screening, physicians and other health professionals should (a) deliver educational messages that increase awareness of risk factors for colorectal cancer and curability of the disease, and (b) elicit from potential screenees a commitment to engage in recommended preventive behaviors. It may also be well to consider "tailoring" messages for past nontesters and past testers, respectively, by emphasizing colorectal cancer risk factors and highlighting curability.

Is evaluation of the right colon necessary prior to cecocystoplasty?

Use of the ileocecal bowel segment in urological surgery has become more widespread. Thorough preoperative evaluation of the bowel is seldom performed. A case is presented in which the intraoperative finding of numerous cecal polyps led to abortion of a planned cecocystoplasty. The literature on fecal occult blood testing and screening methods for colorectal neoplasia was reviewed. Patients are classified into 2 categories, average risk and high risk, according to the relative risk for colorectal neoplasia. The data suggest that the fecal occult blood test, if properly performed, is an adequate screening tool for average risk patients. However, because of the high rate of false negative results this test is inadequate for evaluation of high risk patients. It is recommended that such patients should undergo preoperative screening colonoscopy regardless of the fecal occult blood test result.

Industrial risk factors for colorectal cancer

Colorectal cancer is the second most common malignancy in the United States, and its incidence rates have sharply increased recently, especially in males. Industrial exposures, both occupational and environmental, are important colorectal cancer risk factors that are generally unrecognized by clinicians. Migration studies have documented that colorectal cancer is strongly associated with environmental risk factors. The causal role of occupational exposures is evidenced by a substantial literature associating specific work practices with increased colorectal cancer risks. Industrially related environmental exposures, including polluted drinking water and ionizing radiation, have also been associated with excess risks. Currently, there is a tendency to attribute colorectal cancer, largely or exclusively, to dietary and other lifestyle factors, thus neglecting these industrially related effects. Concerted efforts are needed to recognize the causal role of industrial risk factors and to encourage government and industry to reduce carcinogenic exposures. Furthermore, cost-effective screening programs for high-risk population groups are critically needed to further reduce deaths from colorectal cancer.

Is there a preference for different ways of performing faecal occult blood tests?

Low compliance with faecal occult blood screening reduces the power of clinical trials, potential benefit, and efficiency. It has been proposed that the faecal manipulation required to perform conventional guaiac based tests may be an important factor in low compliance. The aim of this study was to evaluate whether use of a new method (vehicle) of stool collection for the faecal occult blood guaiac test would be preferred to the established standard. A novel self-interpreted test, Early Detector (ED), requires the subject to apply a guaiac/peroxide spray to a stool sample collected simply by wiping the anus with a specimen pad. To determine whether this method would be preferred to the stool manipulation required by Haemoccult (HO) and to compare test validity, employees at a London company were invited to use both tests. Eight-hundred and fifty-seven subjects were shown both tests. Before use, 48% indicated a preference for the method of Early Detector; 24% chose Haemoccult (p less than 0.001), while 28% indicated no immediate preference. Seven-hundred and one performed both tests. After use, 74% preferred ED; 5% preferred HO (p less than 0.001); 21% had no preference (NP). The preference for the ED test method was consistent by sex categories, age groups and occupational class. Logistics, aesthetics, and immediacy of results were the main reasons indicated for choosing ED. Whether the preference for ED could result in higher compliance remains to be proven. Its high positivity (14%), however, would preclude its use as a sole test to determine the need for endoscopic and/or radiologic investigation in the screened patient.

Screening an asymptomatic population for colorectal cancer

The best prospect of realizing a reduction in mortality from colorectal cancer appears to be by presymptomatic detection in a screened population. Presently, the only feasible method of mass population screening is by the detection of faecal occult blood and it is encouraging that all the major trials demonstrate that asymptomatic malignancy may be detected in this way. Furthermore, the screen-detected cancers are generally at an earlier pathological stage than those appearing in control populations. However, a note of caution is required. At the present time it is too early to demonstrate a reduction in mortality from the disease and there is evidence of a length bias, with more of the screen-detected cancers being well differentiated. The results of the large controlled trials will enable the benefits of screening to be viewed objectively and a recommendation for, or against, screening to be made.

Randomised, controlled trial of faecal occult blood screening for colorectal cancer. Results for first 107,349 subjects

To assess the effectiveness of screening by faecal occult blood tests, 107,349 people without symptoms of colorectal disease identified from general practitioner records have been randomly allocated to test and control groups. 53,464 test subjects were invited to carry out the screening test; 27,651 (53%) of the 52,258 who received the tests did so. Further investigation of the 618 (2.3%) with positive tests showed 63 cancers (52% stage A) and 367 adenomas (266 subjects). Rescreening of subjects with negative results every 2 years (9510 first rescreen, 3639 second) has shown a significant fall in the rate of positive results (1.7% of 7344; 0.3% of 2906). Cancers have also been diagnosed in 20 subjects presenting in the interval between a negative test and rescreening, and in 83 non-responders. The incidence of cancer in the control group (123 subjects; 10.6% stage A) was 0.72 per 1000 person-years. Cancers detected by screening were at a less advanced pathological stage, but it is too early to show any effect of screening on mortality from colorectal cancer.

Fecal occult blood testing. Problems, pitfalls, and diagnostic concerns

The diagnostic approach to the asymptomatic patient who has tested positive for fecal occult blood varies among clinicians. Colonoscopic evaluation is the procedure of choice in initiating the workup of patients 50 years of age and older. In younger patients, examination by sigmoidoscopy and barium enema using air for contrast (double contrast study) may be considered as an alternative to colonoscopy as the initial test. Evaluation of the upper gastrointestinal tract should be considered if a colonic source is not detected. The challenge in diagnostic test selection lies in choosing the most appropriate and cost-effective procedure for detecting disease, especially neoplastic lesions.