Any role left for invasive tests? Histology in clinical practice

Introduction Although some patients may consider even a venepuncture “invasive”, in the context of tests for Helicobacter pylori infection this term is usually restricted to those which require gastric biopsy samples. These tests incorporate a range of techniques to show the presence of H pylori in biopsy material and comprise histology, culture, rapid urease tests and, of lesser importance, microscopic examination of smears from biopsy samples or brushings and the polymerase chain reaction (PCR) which by amplifying segments of nucleic acids specific for H pylori can detect very small numbers of bacteria. As only the first three are widely practised, we shall confine our consideration to them. In comparing diagnostic tests it is conventional to examine their sensitivity—the proportion of positives that are correctly identified by the test—and their specificity—the proportion of negatives correctly identified by the test— but there are other factors influencing the general utility of a test which include availability, reproducibility, rapidity, and cost. Furthermore, tests vary in the amount of information they provide in addition to H pylori status.