13C-urea breath test for the diagnosis of Helicobacter pylori infection before treatment:: is citric acid necessary?

Aim. C-13-urea breath test is one of the best methods for the diagnosis of Helicobacter pylori infection. Although a citric acid solution is generally used prior to urea intake, the superiority of this strategy has not been sufficiently demonstrated Thus, our aim was to compare C-13- urea breath test with and without citric acid solution, to evaluate whether C-13-urea breath test can also achieve favourable results when the test meal is omitted. Methods. C-13-urea breath test with and without citric acid were compared prospectively in 53 subjects without prior Helicobacter pylori eradication therapy prescription. Basal samples and at 15: 30': and 45' after taking 100 mg of C-13-urea were obtained. The gold standard for Helicobacter pylori diagnosis was the C-13-urea breath test result with citric acid at 30', and "Delta Over Baseline" values >5 at that time were considered positive. Results. The prevalence of Helicobacter pylori infection was 68%. Mean Delta Over Baseline values with, citric acid at 15: 30' and 45' were. 29.6+/-39, 30.8+/-37 and 24.6+/-27; whereas respective values without citric acid were lower: 14.9+/-22, 12.2+/-17 and 10+/-13 (p<0.001 for all comparisons, Wilcoxon test for paired data). Thus, the area under the curve (constructed with Delta Over Baseline values at different times) with citric acid was 85+/-102, and 37+/-50 without citric acid (p<0.001) Correlation coefficient between Delta Over Baseline values with and without citric acid at 30' was 0.73 (p<0.0001) The percentage of subjects achieving the highest Delta Over Baseline value at 15: 30' and 45' with citric acid was 51%, 30% and 19%, whereas without citric acid it was 51%, 26% and 23% (nonsignificant differences). The area under receiver operating characteristic curve for C-13 urea breath test without citric acid was: 0.98 at 15', 1 at 30' and 0.97 at 45'. The best cut-off point for C-13-urea breath test without citric acid at 30' was anywhere between 3.3 and 3.9 (that is, a lower value than that usually considered with citric acid), with 100% (95% confidence interval, 90-100% sensitivity and 100% (82-100%) specificity. Conclusions. C-13-urea breath test values with citric acid are higher than those obtained without citric acid, although this difference does not imply a diagnostic superiority in untreated patients when considering C-13-urea breath test without citric acid at 30'. Therefore, for the diagnosis of Helicobacter pylori infection in untreated patients, citric acid solution in C-13-urea breath test protocol can be omitted.