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Bleeding patterns in colorectal cancer: the effect of aspirin and the implications for faecal occult blood testing
Insights
Standard 3-day fecal occult blood tests miss many colorectal cancers. Even a 6-day test and aspirin did not fully detect bleeding, indicating a need for improved diagnostic methods.
Area of Science:
- Gastroenterology
- Oncology
- Diagnostic Medicine
Background:
- Colorectal cancer screening often relies on fecal occult blood testing (FOBT).
- The standard 3-day Haemoccult regimen is widely used but its diagnostic adequacy is questioned.
- Tumor bleeding can be intermittent and variable, potentially affecting test sensitivity.
Purpose of the Study:
- To evaluate the diagnostic yield of a 6-day Haemoccult FOBT regimen for colorectal cancer.
- To assess if enteric-coated aspirin administration influences tumor bleeding and FOBT results.
- To determine the sensitivity of FOBT in detecting colorectal cancer-associated blood loss.
Main Methods:
- Fifty patients with colorectal cancer underwent a 6-day Haemoccult test.
- Enteric-coated aspirin was administered during the final 3 days of testing.
- Radiochromium assay quantified blood loss in 25 patients to correlate with FOBT results.
Main Results:
- Thirty percent of tumors were missed by the standard 3-day FOBT; 18% were missed even after aspirin.
- Median daily blood loss was 1.2 ml before aspirin and 2.5 ml after.
- Ten percent of tumors remained persistently negative over the 6-day test period.
Conclusions:
- The standard 3-day Haemoccult test has limited sensitivity for colorectal cancer detection.
- Extending the test to 6 days and including aspirin did not significantly improve diagnostic yield.
- Novel methods are essential to enhance the effectiveness of fecal occult blood testing in colorectal cancer screening.
Abstract:
Faecal occult blood testing for 3 consecutive days is recommended for the detection of colorectal cancer. Is this adequate? Haemoccult tests were performed for 6 days on the faeces of 50 patients with colorectal cancer. Enteric-coated aspirin was given during the final 3 days to see if its systemic effect on coagulation would increase tumour bleeding. In 25 patients blood loss was quantified by radiochromium assay. Bleeding was slight and intermittent with large daily fluctuations in individual patients. Median daily loss before aspirin was 1.2 ml and after aspirin 2.5 ml. Thirty per cent of the tumours were Haemoccult negative using the standard 3-day regimen and 18 per cent were negative after aspirin. Over the 6-day period, 10 per cent were persistently negative. We conclude that new methods are required to improve the diagnostic yield from faecal occult blood tests.