Self-reported dark red bleeding as a marker comparable with occult blood testing in screening for large bowel neoplasms

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Abstract
The study was designed to determine the prevalence of large bowel symptoms in an adult working population and to assess their value in screening for large bowel neoplasms. A symptom questionnaire was sent to workers in two large organizations and the results were compared with faecal occult blood testing in the same individuals using Haemoccult (Eaton Laboratories). Completed symptom questionnaires and Haemoccult test kits were returned by 916 out of a total of 1805 employees over the age of 40 (compliance 50.7 per cent). Twenty-eight (3.1 per cent) were Haemoccult positive and 114 (12.4 per cent) had one or more symptoms. All positives (129 persons) were examined by flexible sigmoidoscopy and barium enema. No cancer was found but 7 patients with adenomas greater than 10 mm diameter were discovered. Each of the 7 patients reported at least one symptom (dark red bleeding in 4, bright red bleeding in 2 and diarrhoea in 1) and 6 were Haemoccult positive. There was no individual with a Haemoccult positive adenoma without symptoms. Predictive values for adenomas over 10 mm for Haemoccult positive tests (21 per cent), self-reported dark bleeding (16 per cent) and diarrhoea (17 per cent), were significantly higher than for other symptoms. The predictive value rose significantly to 46 per cent for Haemoccult-positive patients who in addition had at least one symptom (P < 0.05) and to 57 per cent for Haemoccult positive with dark bleeding. These combinations of Haemoccult- and symptom-positive results increased the specificity of 97.6 per cent for Haemoccult alone to values over 99 per cent without reducing sensitivity. These results indicate first that occult blood testing may not be identifying ‘asymptomatic’ cases as often as has been presumed by others. Second, the addition of self-reported large bowel symptoms improves the performance of Haemoccult as a screening test. Finally, the presence of dark red bleeding, which can be ascertained using a symptom questionnaire, has a predictive value for adenomas over 10 mm, comparable with Haemoccult and thus may have a separate role in screening.