Diagnostic value of a guaiac occult blood test and faecal alpha 1-antitrypsin

Abstract

This study evaluates the diagnostic accuracy of a faecal occult blood test and faecal antitrypsin in the investigation of patients with gastrointestinal symptoms or iron deficiency anaemia. One hundred and seventy nine patients with either iron deficiency anaemia (n=67), changed bowel habit and aged >39 years (n=107), or a history suggestive of melaena (n=5) provided faecal samples. After investigation, 32 patients had a diagnosis of possible gastrointestinal bleeding and 139 patients had no evidence of gastrointestinal bleeding. Eight patients had a cause of enteric protein loss in the absence of gastrointestinal bleeding and were excluded from subsequent analysis. The faecal α1-antitrypsin test was diagnostically more accurate than the guaiac test in identifying probable gastrointestinal bleeding (82% and 72% respectively, p<0.05). This faecal α1-antitrypsin test was also more specific (83% and 72% respectively, p<0.05), but was not significantly more sensitive (78% and 72% respectively). The sensitivity of these tests was insufficient to recommend their use for most patients in this study.