Evaluation of diagnostic accuracy of two rapid stool antigen tests using an immunochromatographic assay to detect Helicobacter pylori.

OBJECTIVES

The stool antigen assay for H. pylori infection diagnosis with monoclonal antibodies is a simple and recommended technique by the Maastricht V/Florence consensus report. Recently, Pylori K-Set K-1219 (Coris Bioconcept Sprl, Belgium) and HP-F23 (Symbiosys, Brazil) have been made commercially available in Brazil. Thus, the aim of this study was to evaluate the diagnostic accuracies of these two rapid stool antigen tests by immunochromatographic assays (index tests) for the clinical practice.

DESIGN AND METHODS

A total of 98 patients who underwent upper gastrointestinal endoscopy and C-urea breath test entered the study. H. pylori infection status was defined by the combination of the rapid urease test and the C-urea breath test (reference standard). Two observers who were aware of H. pylori status performed the reading of index tests. Diagnostic accuracy (sensitivity, specificity, positive predictive value, negative predictive value with 95% confidence intervals, positive likelihood ratio, negative likelihood ratio and kappa index measure of agreement) were determined.

RESULTS

The index tests where in perfect agreement with the H. pylori status with kappa values of 0.87 for Pylori K-Set K-1219 and 0.92 for HP-F23. The sensitivity of HP-F23 was 97.9% (IC95%: 87.5-100) and specificity was 93.8% (IC95%; 84-97.2).The positive likelihood ratio was 15.8, and the negative likelihood ratio was 0.02. The Pylori K-Set K-1219 had a sensitivity of 87.7% (IC95%: 74.5-94.9) and a specificity of 100% (IC95%: 91.6-100); the positive likelihood ratio was ∞, and the negative likelihood ratio was 0.1. The test line on the cassette device of HP-F23 was stronger than of the Pylori K-Set K-1219.

CONCLUSION

The HP-F23 test performed better in clinical practice. Nonetheless, the C-urea breath test is more reliable technique. Moreover, caution must be paid to the trace or clear pale test line readings that were observed in false positive and false negative results, leading to incorrect management of the patient.