Heads or tails in a positive faecal occult blood test

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.

Detection and diagnosis of blood in feces and urine: an overview

BACKGROUND

Detection of blood in feces or urine has long been regarded as an indicator of patient's state of health. The ease with which feces or urine may be obtained and patient's willingness to provide the specimen make detection of fecal occult blood or urine analysis one of the most commonly performed screening examinations. Historically, the inspection of feces or urine for diagnostic purpose has been practiced for centuries. Of late, management of renal or urinary tract abnormalities or investigation of anemia, gastrointestinal diseases and for early detection of colorectal cancer has assumed greater importance.

METHODS

The never-ending list of techniques for the diagnosis of disorders producing bleeding such as urine microscopy, urine cytology, urine based marker test, cytoscopy, ultra sonography, computed tomography, magnetic resonance imaging, to mention a few, and four categories of detection of fecal occult blood namely, radioanalytical, physical, immunochemical and chemical methods makes the study very interesting.

PURPOSE

This review attempts to overview various techniques, methods and methodologies for the diagnosis and detection of blood in feces and urine, in the direction of looking at past and current tests with an eye on future needs.

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.