Isotope ratio mass spectrometry (IRMS) versus laser-assisted ratio analyzer (LARA) - A comparative study using two doses of [C-13]urea and two test meals for pre- and posttreatment diagnosis of Helicobacter pylori infection

This study was carried out to compare the measurements and the diagnostic a ccuracy of the traditional expensive IRMS and the new economical LARA syste m using two doses of [C-13]urea + two different test meals in patients unde rgoing upper gastrointestinal endoscopy, both before and after anti-Helicob acter treatment. A total of 354 dyspeptic patients underwent endoscopy with gastric biopsies to diagnose H. pylori infection by CLO-test and histology . No patients had taken antibiotics, bismuth, or antisecretory drugs in the 4 weeks before testing. After overnight fasting, breath samples were colle cted simultaneously in both plastic and glass tubes at baseline and at 30 a nd 60 min after urea ingestion. In 237 patients 100 mg [C-13]urea + Ensure and in 117 patients 75 mg [C-13]urea + citric acid were given. The test was also performed with the two urea dosages and meals in 67 and 64 infected p atients, respectively, four weeks after anti-Helicobacter therapy. H. pylor i was considered eradicated when both biopsy-based tests were negative. A d elta value >5 parts per thousand was considered positive. Breath samples wi th insufficient CO2 levels at both 30 and 60 min were excluded from final a nalysis (N = 37 in pre- and N = 8 in posttreatment). There was excellent ag reement between overall delta values of the two machines with both [C-13]ur ea 100 mg + Ensure and [C-13]urea 75 mg + citric acid. The 95% CI of the di fference against the mean was wider with the former (mean -1.3, +6.3, and - 9.4) than with the latter urea dosage and test meal (mean -1.2, +5.2 and -8 .1). LARA and IRMS were equally effective (P = NS) in distinguishing infect ed from uninfected patients before therapy using both doses of [C-13]urea a nd lest meals (sensitivity ranged from 95% to 99% and specificity from 95% to 97%). This good performance was maintained in the posttreatment phase (s ensitivity ranged from 90% to 100% and specificity from 90% to 97%), withou t any statistical difference among the various combinations (P = NS). The L ARA system is a valid alternative to IRMS in the diagnosis of II. pylori in fection. Both machines provide highly reliable results after 30 min, so tha t the 60 min sample can be avoided. The dose of 75 mg + citric acid suffice s to ensure an accurate UBT. The test performed with both devices and [C-13 ]urea dosages is very effective also for posttherapy evaluation of H. pylor i status.