Introduction Rapid access clinics exist for patients who are symptomatic from symptoms suggestive of colorectal cancer.
Eighty-five to 90% of such symptomatic patients have non- malignant pathology. This results in unnecessary and hurried use of expense resources.
Working on the principle that colonic tumours bleed, an immunological faecal occult blood test (FOBTi) – which uses antibodies specific for human haemoglobin – can identify patients who may have colorectal cancer.
Aim To determine the sensitivity and specificity of FOBTi in detecting patients with colorectal cancer (in the absence of covert per rectal bleeding) referred to rapid access colorectal clinics.
Method A prospective cohort study was performed on patients referred to Rapid Access Colorectal clinic.
A digital rectal exam (DRE) was performed on each patient and faecal sample obtained for FOBTi testing. Colonic investigations were arranged for each patient and results correlated to the FOBTi result.
Results To date 107 FOBTi samples with complete colonic investigations are available.
Twenty-seven patients tested FOBT positive, 81 FOBT negative.
In the positive group, 44% had cancer (58% rectal cancer; 25% left sided cancer, 8% right sided cancer, 8% transverse colon cancer). Other diagnoses are shown below:
In the FOBTi negative group no cancers were detected on further investigations.
Using these results, FOBTi has a sensitivity of 100% and 84% specificity. The positive predictive value is 44% and negative predictive value 100%.
Conclusion Immunological FOBTi is an instant and objective test which utilises immuno-chromatography to detect blood loss in the stool. When used with DRE in patients with clinical symptoms it has 100% sensitivity and 84% specificity. A negative result means patients are unlikely to have a cancer diagnosis, which may lead a reduction in unnecessary investigations.
Disclosure of interest None Declared.
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