Comparison of serum, salivary, and rapid whole blood diagnostic tests for Helicobacter pylori and their validation against endoscopy based tests.

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Abstract
BACKGROUND: A rapid, reliable, and accurate test for the diagnosis of infection with Helicobacter pylori is needed for screening dyspeptic patients before referral for endoscopy. AIM: To compare a new rapid whole blood test (Helisal rapid blood, Cortecs), two serum enzyme linked immunosorbent assays (ELISAs; Helico-G, Shield and Helisal serum, Cortecs), and a salivary assay (Helisal saliva, Cortecs), with slide biopsy urease, 13C-urea breath test, and histology. METHODS: Three hundred and three consecutive dyspeptic patients attending for gastroscopy underwent two antral biopsies for histology, and one for rapid slide biopsy urease test for assessment of H pylori status. Blood and saliva were also collected. One hundred of the patients also underwent a 13C-urea breath test. Gold standard positives were defined as those with at least two positive tests among slide urease, breath test, or histology, and gold standard negatives as those with all these (or two when the breath test was not done) negative. RESULTS: Of 300 patients (median age 63, range 28-89) eligible for analysis, 137 (46%) were gold standard positives, of which Helisal rapid blood identified 116, Helico-G 129, Helisal serum 130, and Helisal saliva 120; 137 (46%) were gold standard negatives of which the number falsely identified as positive was 30 by Helisal rapid blood, 45 by Helico-G, 41 by Helisal serum, and 41 by Helisal saliva. Sensitivities and specificities were: for the whole blood test 85% and 78% respectively; for Helico-G 94% and 67%, for Helisal serum 95% and 70%, and for Helisal saliva 84% and 70%. CONCLUSIONS: If endoscopy had been undertaken only on patients with positive tests two of 16 duodenal ulcers would have been missed if the Helisal rapid blood test was used, and one if any of the ELISA tests were used. None of the blood tests would have missed any of six gastric ulcers, but the salivary test would have missed one.