Tests for Helicobacter pylori infection: a critical appraisal from primarycare

Background. Testing of patients for Helicobacter pylori infection is common in primary care settings. The accuracy of such tests has been assessed and critical appraisal of this literature can inform the clinical management o f patients suspected of being infected with H.pylori. Methods. Literature evaluating the accuracy of diagnostic tests for H.pylor i infection was sought as part of a systematic review of literature concern ing the management of patients infected with H.pylori. Studies were apprais ed and estimates of sensitivity and specificity were extracted. Positive an d negative likelihood ratios (LRs) were calculated and the implications for post-test probabilities are reported. Results. The sensitivity, specificity, LR+ and LR- for H.pylori infection t ests are: [C-13]urea breath test (UBT), 96.5, 96, 24 and 0.04; [C-14]UBT, 9 7.5, 95.5, 21 and 0.03; serology, 91, 89.5, 8 and 0.11; near patient tests, 77, 74, 3 and 0.31; and meta-analysis of serology, 85, 79, 4 and 0.19. The range of pre-test probabilities of H.pylori infection in which the diagnos tic tests were useful, estimated from primary studies, were: [C-13]UBT, 20- 90%; [C-14]UBT, 20-99%; serology, 30-80%; and near patient tests, 50-60%. Conclusions. Tests for H.pylori infection are useful in primary care when t he pre-test probability of infection is neither too high nor too low. This indicates that the tests may not be useful for screening purposes but may h elp with differential diagnosis. Outside moderate pre-test probability rang es, the chances of a result being false is high, and such patients should e ither receive eradication without prior testing (if the probability of infe ction is sufficiently high) or the test result should be reconfirmed. When the pre-test probability falls below similar to 20%, a positive test result is unreliable. If the pre-test probability is above similar to 80%, a nega tive test result is unreliable. Clinical selection of patients needing test ing should be used to limit testing to individuals with pre-test probabilit ies within these ranges. The choice of diagnostic H.pylori test should be i nfluenced by the H.pylori infection rate in the population being tested and the test characteristics. Recommendations for the use of tests, especially near patient tests, should be reconsidered. This critical appraisal suppor ts the recommendations of the European Society for Primary Care Gastroenter ology guidelines, arrived at by consensus, for testing for H.pylori infecti on in primary care.