Accuracy of CLOtest after Helicobacter pylori therapy

The accuracy of rapid urease testing after Helicobacter pylori therapy has not been widely studied and might be diminished because of decreased numbers of organisms. We assessed CLOtest results after therapy in two randomized, double-blind trials.

A total of 233 patients (in two separate studies) with true-positive baseline CLOtests (by histology or culture) received 2 weeks of omeprazole/amoxicillin, omeprazole, or amoxicillin. In study 1, patients received an additional 2 weeks of omeprazole therapy (20 mg/day) or placebo; no additional therapy was given in study 2. Endoscopy was repeated 4 weeks after completion of therapy in both studies. A diagnosis of cure required at least two negative endoscopic biopsy tests (histology, culture, CLOtest) and no positive tests.

After therapy, 178 patients (76%) remained positive for H. pylori by histology and/or culture for both studies combined. Post-therapy CLOtest sensitivity was 86% and specificity was 95%. Sensitivity was poorer in patients after dual therapy than after monotherapy in both study 1 (68% vs. 89%; p = 0.03) and study 2 (75% vs. 94%; p = 0.03).

CLOtest sensitivity after therapy was lower than expected in our large group of patients with baseline true-positive CLOtests. In addition, sensitivity was lower after the use of more effective therapy (i.e., dual therapy as compared with monotherapy). Although most patients with unsuccessful treatment will be identified with the CLOtest alone, a negative result should not be taken as diagnostic of eradication.