Validation of a rapid stool antigen test for diagnosis of Helicobacter pylori infection

Abstract

SUMMARYThe aim of this study was to validate the rapid lateral flow Helicobacter pylori stool antigen test (One step H. pylori antigen test, ACON laboratories, San Diego, USA; Prime diagnostics, São Paulo), using 13 C-Urea Breath Test as the gold standard for H. pylori infection diagnosis. A total of 98 consecutive patients, asymptomatic or dyspeptic, entered the study. Sixty-nine were women, with a mean age of 45.76 ± 14.59 years (14 to 79 years). In the H. pylori-positive group, the rapid stool antigen test detected H. pylori antigen in 44 of the 50 positive patients (sensitivity 88%; 95% CI: 75.7-95.5%), and six false-negative; and in the H. pylori-negative group 42 presented negative results (specificity 87.5%; 95% CI: 74.7-95.3%), and six false-positive, showing a substantial agreement (Kappa Index = 0.75; p < 0.0001; 95% CI: 0.6-0.9). Forty four of fifty patients that had positive stool antigen were H. pylori-positive, the PPV of the stool antigen test was 88% (95% CI: 75.7-95.5%), and 42 patients with negative stool antigen test were H. pylori-negative, the NPV of the stool antigen test was 87.5% (95% CI: 74.7-95.3%). We conclude that the lateral flow stool antigen test can be used as an alternative to breath test for H. pylori infection diagnosis especially in developing countries.

Is the Immunocromatographic Fecal Antigen Test Effective for Primary Diagnosis of Helicobacter Pylori Infection in Dyspeptic Patients?

“…The results of this imunocromatographic test are in disagreement with the immunoassay tests executed in Brazil (2,3,11,13,14,(16)(17)(18)21). Our results are also in disagreement with some results obtained even in different areas of the world, by immunocromatographic assay (4,9,18) .…”

“…False-positive results may also have occurred due to the presence of a coccoid form of H. pylori. This form despite to be a morphological manifestation of bacterial death, induces antigen detected by the test (21) .…”

“…Institutional Internal Review Board approved the protocol study under the number CAAE 11979613.7.0000.5346. We excluded patients treated with antibiotics in the last 30 days or proton pump inhibitors (PPIs) in the last two weeks (21) , as well as patients with gastric cancer, gastrectomy, bleeding disorder, acquired immunodeficiency syndrome, congestive heart failure, renal failure, and chronic liver disease.…”

“…Due to these characteristics, the use of FAT by immunochromatography in developing countries is attractive. To the best of our knowledge, only nine studies (2,3,11,13,14,(16)(17)(18)21) in the past ten years evaluated FAT to diagnosis H. pylori infection in Brazil, most of them used immuno-enzymatic assay and only one used immunochromatography (18) .…”

3rd BRAZILIAN CONSENSUS ON Helicobacter pylori

“…The most commonly used serological tests are those performed by ELISA, as previously validated in Brazil (146,169) . To control bacteria eradication in the test-and-treat strategy, only the labeled urea breath test and a fecal antigen survey are recommended, both of which have also been validated in Brazil already (26,189) .…”