[Optimization of the tagged urea test for the detection of H. pylori in patients with dyspepsia]. / Optimización de la prueba de la urea marcada para la detección de H. pylori en pacientes con dispepsia.

ABSTRACT

Helicobacter pylori (Hp) has been associated to gastritis, peptic ulcer, gastric cancer, and other gastrointestinal disorders. The 14C-urea breath test (UBT) has been proposed as a simple and noninvasive method for its detection, and has recently been implemented in our institution. To optimize our resources, we performed a sensitivity analysis to determine the minimal sampling and duration of testing required, and to establish objective criteria for its interpretation. With this purpose, endoscopy, antral biopsy and UBT were performed in 104 dyspeptic patients. For the UBT, a basal breath sample was taken before the administration of 10 microCi of 14C-urea and followed by sequential breath sampling at 5, 15, 30 and 60 minutes. Considering histologic findings as the gold standard, receiver operating characteristic (ROC) curves were constructed for the following three 14CO2 excretion strategies excretion by sample, maximum excretion, and cumulative excretion. Hp was detected in 74 (71%) of the patients, and its presence coincided with significantly higher 14CO2 excretion than in the Hp negative (p < 0.001). The three excretion strategies were comparable in terms of diagnostic accuracy, but the most efficient results were given by the 15 minute sample. With a cut-off point of > or = 1.7%, the sensitivity and specificity of this sample was > or = 83%, the positive and negative predictive values were 93% and 68%, and the accuracy was 84%. We conclude that UBT can be completed with a single breath sampling at 15 min, and its results objectively interpreted as positive if the 14CO2 excretion is > or = 1.7%.