Assessment of faecal occult blood loss by qualitative and quantitative methods

Various methods exist for the assessment of faecal occult blood loss in a patient with suspected gastrointestinal blood loss.

The present study examined the effectiveness and financial implications of a qualitative guaiac-based method (Haemoccult) of faecal occult blood detection and a quantitative measure of haeme-derived porphyrins (Hemoquant) in 184 patients who underwent assessment of faecal blood loss by both methods over a three year period during assessment of iron deficiency anaemia.

At least one Haemoccult test was positive in 72.2% of patients while Hemoquant was suggestive of significant blood loss (> 2mg haemoglobin/g faeces) in 29.9%. Patients underwent a total of 324 further endoscopic or radiological investigations of which 76.5% demonstrated no abnormality. A diagnosis was reached in 60 patients (32.6%). A significant potential source of gastrointestinal bleeding was found in 48 patients (26.1%). Hemoquant achieved a sensitivity of 62.5% and a specificity of 81.6% while with Haemoccult it was 85.4% and 32.4%, respectively. Hemoquant was normal in 18 patients with significant gastrointestinal conditions including peptic ulcers and colonic polyps. While Haemoccult only missed 7 lesions, two of these were colonic cancers. The quantitative nature of the Hemoquant test gave little clue as to diagnosis.

Neither of the tests examined was ideal but Hemoquant had an overall better performance and further investigation of patients with evidence of blood loss from this test should be mandatory.