The clinical role of stool test (HpSA) in noninvasive diagnosis of Helicobacter pylori infection

Helicobacter pylori (H. pylori) causes a chronic gastric infection, which is usually life-long and many epidemiological studies have shown that this is probably one of the most common bacterial infections throughout the world, involving 50% of the population in developed countries and up to 80-90% of the population in developing regions. It is therefore clean that nowadays the diagnosis of H. pylori infection today represents, at the very least, a key step in the management of many of the patients referred to the gastroenterologist. Due to the widerange and relevance of pathologies possibly related to infection (including malignancies), it also harbours the potential to become a major health problem. Up to now, there were only two widely available non-invasive methods: 1) 13C or 14C labelled urea breath test and 2) serology (which is based on the detection of a specific anti-H. pylori immune response, mostly by IgG antibodies, in patient's serum). Over the last few years H. pylori has been detected in the culture of stool samples but viable organisms are present only in a small percentage of cases. Despite the difficulties encountered in culture from stool samples, the fact that the organism was present at all raised the possibility of developing a new non-invasive diagnostic test based on the detection of bacterial antigen in stool. Over the last two years an enzymatic immunoassay (EIA), which detects the presence of H. pylori antigen in stool specimen has become available (HpSA(TM)- H. pylori Stool Antigen Meridian Diagnostics Inc., Cincinnati USA) and begun to be used in clinical practice to evaluate its performance compared to that of other currently available diagnostic tests. The HpSA test has recently received approval from the United States Food and Drugs Administration (FDA) for two indications for use: 1) diagnosis of H. pylori infection in adult symptomatic patients and 2) monitoring response and post-therapy in adult patients. The test utilises polyclonal anti-H. pylori capture antibody absorbed in microwells. It is clear that such a test, which detects bacterial antigen in an actual ongoing infection, is theoretically useful not only for screening, but also as an early predictor of successful treatment. This review will briefly consider the currently available evidence supporting a possible role for this non-invasive diagnostic test.