Effect of iron on the guaiac reaction

Evaluation and treatment of gastrointestinal bleeding in patients taking anticoagulants presenting to the emergency department

This manuscript is a consensus document of an expert panel on the Evaluation and Treatment of Gastrointestinal Bleeding in Patients Taking Anticoagulants Presenting to the Emergency Department, sponsored by the American College of Emergency Physicians.

Patient-care questions that physicians are unable to answer

OBJECTIVE

To describe the characteristics of unanswered clinical questions and propose interventions that could improve the chance of finding answers.

DESIGN

In a previous study, investigators observed primary care physicians in their offices and recorded questions that arose during patient care. Questions that were pursued by the physician, but remained unanswered, were grouped into generic types. In the present study, investigators attempted to answer these questions and developed recommendations aimed at improving the success rate of finding answers.

MEASUREMENTS

Frequency of unanswered question types and recommendations to increase the chance of finding answers.

RESULTS

In an earlier study, 48 physicians asked 1062 questions during 192 half-day office observations. Physicians could not find answers to 237 (41%) of the 585 questions they pursued. The present study grouped the unanswered questions into 19 generic types. Three types accounted for 128 (54%) of the unanswered questions: (1) "Undiagnosed finding" questions asked about the management of abnormal clinical findings, such as symptoms, signs, and test results (What is the approach to finding X?); (2) "Conditional" questions contained qualifying conditions that were appended to otherwise simple questions (What is the management of X, given Y? where "given Y" is the qualifying condition that makes the question difficult.); and (3) "Compound" questions asked about the association between two highly specific elements (Can X cause Y?). The study identified strategies to improve clinical information retrieval, listed below.

CONCLUSION

To improve the chance of finding answers, physicians should change their search strategies by rephrasing their questions and searching more clinically oriented resources. Authors of clinical information resources should anticipate questions that may arise in practice, and clinical information systems should provide clearer and more explicit answers.

From Colonic Polyps to Colon Cancer: Pathophysiology, Clinical Presentation, and Diagnosis

Epidemiologists, basic researchers, clinicians, and public health administrators unite! Develop and implement a simple, safe, and effective preventive and screening test for colon cancer. The public will willingly and enthusiastically accept such a test. Many thousands of lives are at stake every year.

The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps

A review of the pathophysiology, clinical presentation, and diagnosis of colon cancer and colonic polyps is important and timely. This field is rapidly changing because of breakthroughs in the molecular basis of carcinogenesis and in the technology for colon cancer detection and treatment. This article reviews colon cancer and colonic polyps, with a focus on recent dramatic advances, to help the pri-mary care physician and internist appropriately refer patients for screening colonoscopy and intelligently evaluate colonoscopic findings to reduce the mortality from this cancer.

Screening of patients with acute infectious diarrhoea: evaluation of clinical features, faecal microscopy, and faecal occult blood testing

BACKGROUND

For optimal management of acute infectious diarrhoeal diseases, it is necessary to utilize a screening process to distinguish between invasive and non-invasive diarrhoeas. The aim of this study was to compare the diagnostic utilities of clinical features, faecal microscopy (FM), and faecal occult blood testing (FOBT) in distinguishing invasive diarrhoeas from non-invasive ones.

METHODS

A total of 1008 patients with acute diarrhoea were evaluated. Rectal swabs were cultured for Salmonella, Shigella, and Vibrio species; rectal swabs from 109 of these patients were also examined for Campylobacter, enterotoxigenic Escherichia coli, and rotavirus species. Isolation of faecal enteropathogens served as the gold standard. FOBT was performed with a commercial modified guaiac test. Specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and likelihood ratio were compared.

RESULTS

Among the 1008 patients 402 with a single identified enteropathogen were available for analysis. Invasive and non-invasive enteropathogens were isolated from 262 (65.2%) and 140 (34.8%) cases, respectively. The presence of visible blood in faeces was almost a pathognomonic sign of invasive diarrhoea but had poor sensitivity. Clinical features were useful but inadequate in differentiating patients with non-bloody diarrhoea (74% of patients) into invasive and non-invasive categories. The sensitivities, specificities, PPVs, and NPVs of FM and FOBT were 75%, 77%, 58%, 88%, and 85%, 68%, 53%, and 91%, respectively.

CONCLUSION

The presence of visible blood in faeces is a highly specific clinical feature of invasive diarrhoea but suffers from low sensitivity. In non-bloody diarrhoea FOBT is a valuable screening test and is comparable to FM, particularly when interpreted in the clinical context.

Screening for colorectal cancer

Randomized, controlled trials have shown with certainty that screening for colorectal cancer reduces morbidity and is cost-effective. Factors that increase the risk of colorectal cancer include a personal or family history of adenomatous polyps or colorectal cancer, certain genetic syndromes and chronic inflammatory bowel disease.

Colorectal cancer screening

The decision whether to launch a screening program in asymptomatic patients of average risk for colorectal cancer and the selection of the appropriate protocol for screening are complex issues. There are still many unanswered questions. Many organizations such as the American Cancer Society, the World Health Organization Collaborating Center for the Prevention of Colorectal Cancer, and the U.S. National Cancer Institute advocate screening with annual Hemoccult tests and screening with flexible sigmoidoscopy every 3 to 5 years in patients more than 50 years of age. The U.S. Preventive Services Task Force, the Canadian Task Force on Periodic Health Examination, and the International Union Against Cancer have not recommended screening asymptomatic average-risk patients for colorectal cancer. One study showed a small but significant benefit (3 per 1000) of the rehydrated annual Hemoccult test in reducing mortality from colorectal cancer. To embark on a mass screening strategy as recommended, however, would require significant costs, increases in physician training, improved access to the requisite technology, and enhancements in patient and physician compliance. Furthermore, the high false-positive rates of the rehydrated Hemoccult tests would lead to many unnecessary tests, causing greater expense as well as patient discomfort and anxiety. It is, therefore, premature to recommend mass screening for colorectal cancer in asymptomatic individuals at this time. Further research is needed to identify risk factors (such as genetic markers) better and to develop and evaluate screening strategies targeted at those with high risk for colorectal cancer. In the meantime, efforts at primary prevention for the general population should be increased (through nutrition and exercise). Patients over the age of 50 who desire screening should be given information of the benefits and risks of screening and together with their physicians decide on a screening strategy that suits their needs and values.

Iron overdose and detection of gastrointestinal bleeding with the hemoccult and gastroccult assays

STUDY OBJECTIVE

To determine the ability of the Hemoccult and Gastroccult tests (SmithKline Diagnostics) to detect blood in vitro in whole-bowel irrigation (WBI) solution.

INTERVENTIONS

One tablet of ferrous gluconate 324 mg, ferrous sulfate 325 mg, or ascorbic acid 500 mg; or one Materna prenatal vitamin tablet (Lederle Laboratories) was dissolved in 30 mL of Colyte. Colyte alone and each test solution were tested with Hemoccult and Gastroccult slides, then retested at pH values of 3 and 8. Fresh solutions were then spiked with blood and tested with Gastroccult slides. Materna and ascorbic acid solutions were spiked with blood, then tested with Hemoccult slides.

RESULTS

Positive results were difficult to detect on Gastroccult slides. Hemoccult slides were falsely positive for solutions containing only iron and falsely negative for blood-spiked samples containing ascorbic acid.

CONCLUSION

Both the Hemoccult and Gastroccult tests may be unreliable in detecting GI bleeding in cases of iron overdose treated with WBI.

Value of faecal alpha-1-antitrypsin, haemoglobin and a chemical occult blood test in the detection of gastrointestinal disease

Specimens from hospital out-patients and in-patients sent for faecal occult blood tests were also analysed for faecal alpha-1-antitrypsin and faecal haemoglobin. 453 stool specimens from 222 patients were analysed. The clinicians were only aware of the faecal occult blood test results, and diagnoses were made using conventional clinical and investigative criteria. Gastrointestinal bleeding or putative sites of bleeding were diagnosed in 98 patients, whereas in 81 patients putative sites of bleeding were not found or other cause of anaemia diagnosed. In 41 patients there was insufficient information to reach a definitive diagnosis. Comparison of the 3 faecal tests using these grouping methods showed that faecal alpha-1-antitrypsin performed best, with an accuracy of 89%, specificity of 90% and sensitivity of 88%, all significantly better (P < 0.001) than the faecal occult blood test (68%, 60% and 73%, respectively). There was no significant difference between the performance of the faecal occult blood and faecal haemoglobin tests. Faecal alpha-1-antitrypsin measurement may be a useful investigation in situations where a faecal occult blood test would normally be requested.

Wide gastric antrum in patients with non-ulcer dyspepsia. Effect of cisapride

Fasting antral area was examined by ultrasonography in 40 healthy subjects and in 106 patients with non-ulcer dyspepsia (NUD) and erosive prepyloric changes (EPC) before and after treatment with cisapride or placebo. The patients were examined twice, first after a run-in period of 14 days of placebo and then after 14 days of cisapride, 10 mg three times daily, or placebo. The relaxed width of the antral area was measured in two sections: a vertical section in which the antrum, the superior mesenteric vein, and the aorta were visualized simultaneously, and a horizontal section that included the pylorus and the middle of the antrum up to 5 cm proximal to the pylorus. The mean antral area was wider (p less than 0.001), both in vertical and horizontal sections, in patients with NUD and EPC than in controls. The antral area in NUD patients was wider (p less than 0.05) in smokers than in non-smokers. The area tended to decrease during treatment with cisapride (p = 0.08). Bloating was the only symptom significantly associated with a wide antral area (p = 0.01). The results suggest a relationship between a wide fasting antral area and NUD with EPC.

Does nicotine administration influence intragastric acidity?

Smokers have an increased incidence of duodenal ulcer with a high relapse rate whether they receive maintenance therapy with H2-receptor antagonists or not. They also tend to be slow healers. The etiology behind this is still unknown, and there is general disagreement as to whether smoking affects gastric secretion. In an earlier study we found a small but significant decrease in intragastric pH a short time after smoking a cigarette. The aim of the present investigation was to study whether intragastric pH changed during nicotine administration per se. Nicotine was given as a nasal spray to eight healthy smokers. Nicotine did not induce any acute detectable changes in gastric acidity when the 5-min period before spraying was compared with the 35-min period after spraying (median pH, 1.47 (25-75 percentiles, 1.40-2.32) and 1.55 (25-75 percentiles, 1.42-2.06), respectively). When different time periods during a day with hourly nicotine administration were analyzed, and the results compared with those of a similar day when placebo was given, nicotine was found to impair postprandial gastric neutralization. Median pH during the lunch hour was 1.93 (25-75 percentiles, 1.80-2.37) after nicotine and 2.86 (25-75 percentiles, 2.37-3.70) after placebo; p less than 0.025. Possible explanations for this might be nicotine-mediated effects on gastric motility or gastrin release.

Colon-cancer screening in dialysis patients

The usefulness of colon-cancer screening using stool-guaiac testing has been established in large control populations, but not in dialysis patients. In 72 asymptomatic dialysis patients [51 treated with hemodialysis (HD), and 21 with peritoneal dialysis (PD)] who underwent outpatient stool occult blood testing, the test result was positive in 11 (15%) patients (8 HD and 3 PD). Eight of the 11 were investigated further by colonoscopy and, when deemed necessary by the treating physician, esophagogastroduodenoscopy and/or barium enema were also performed. A site of active bleeding was identified in three of the eight patients (hemorrhoids, telangiectasia, ulcerative colitis). In each of the five other patients, potentially bleeding lesions were identified: colonic polyps (two malignant and two benign) in four patients. Barrett's esophagus in one, diverticulosis in two, and colonic vascular deformities in two. These results were compared with those of a large ongoing fecal occult blood screening program in which the prevalence of positive stool occult blood tests is 5% and in which 42% of the positive patients have colonic neoplasms. Thus, although the baseline incidence of positive guaiac tests may be higher in dialysis patients than in nonuremic controls, our results suggest that stool guaiac testing of dialysis patients may not only be useful in detecting colonic polyps, but may also identify other previously unsuspected causes of gastrointestinal bleeding.

Haem in the gut. Part II. Faecal excretion of haem and haem-derived porphyrins and their detection

Only a fraction of haem (ferroprotoporphyrin) finding its way into the gut lumen is absorbed; the major portion enters the colon. There, unabsorbed haem, together with any haem of haemoproteins shed directly into the colonic lumen as haemoglobin or other haemoproteins, are converted by bacteria to a range of haem-derived porphyrins (HDP) lacking iron. This conversion is a slow and incomplete process and the amount converted in this way depends on colonic transit rate, site of bleeding and amount of luminal haem. As a consequence, faeces contain variable proportions of haem and HDP. The guaiac and tetramethylbenzidine tests give a qualitative index of faecal blood; they depend on the pseudoperoxidase activity of intact haem and cannot detect HDP. These tests perform better for large bowel bleeding than for more proximal bleeding. The fluorimetric HemoQuant assay quantitates both haem and HDP; it performs well for both proximal and distal bleeding. Neither type of test can allow for intestinal absorption of haem or HDP. Quantitation of gastrointestinal bleeding derived from measurement of faecally excreted haem and HDP is, therefore, likely to underestimate haem delivered into the gut lumen. In a given clinical situation, the choice of a haem-dependent occult blood test must take into account the possibility of colonic conversion of haem to HDP and the possible value of quantitation as opposed to qualitative detection.