3.4 | Evaluation of clinical utility
The clinical utility of RAC was assessed by utilizing like-hood ratios to simulate a Fagan nomogram. With a 46% pretest probability of H. pylori infection, the posttest probabilities of H. pylori infection were 77% (with a positive test result) and 3% (with a negative test result). The Fagan nomogram revealed that the posttest probability increased by 31% in patients with a positive test but decreased by 43% in patients with a negative test, suggesting that RAC was useful in clinical practice (Figure 4 ). Furthermore, the likelihood ratio scattergram showed a PLR of <10 and an NLR of <0.1, suggesting that RAC can be used as an endoscopic marker for exclusion rather than confirmation of H. pylori infection (Figure 5 ).