Serodiagnosis of Helicobacter pylori: evaluation of a rapid, miniaturized immunochromatographic test

Abstract

Diagnosis and successful eradication of Helicobacter pylori infection has been shown to be significantly related to symptom improvement in patients affected by chronic gastritis, duodenal and gastric ulcer. There is, therefore, an increasing need for the development of new, easy to use, reliable and non-invasive techniques to detect this organism. One such test is Flex-Sure (SmithKline Diagnostics Inc., United States), a new, rapid immunochromatographic test which requires a drop of the patient's serum to be placed on the absorbent pad of a strip. If specific antibodies to H. pylori are present a red colour line appears. The present study compared Flex-Sure with a homologous quantitative immunoenzymatic test (HM-CAP, EPI, US) using the same antigen (high molecular weight protein), the second generation GAP test (Bio-Rad, USA), a rapid urease test, culture and histology in a cohort of dyspeptic patients. We produced a semiquantitative visual scale with which to perform this comparison. Our results show that Flex-Sure possesses a sensitivity of 96.1%, a specificity of 73.9%, an overall accuracy of 78.8%, a positive predictive value of 72% and a negative predictive value of 91.6%. It showed a highly significant correlation with histological and cultural results (P < 0.001), and with the other serological tests (P < 0.0001). Based on our data we conclude that Flex-Sure may yield quick (within 4 min), simply readable, qualitative, and according to our colourimetric scale, even semiquantitative results. Furthermore, it does not require any sample dilution, any particular equipment, or any specialized training for the operator.