Twenty-four-hour intragastric pH-metry: evidence of nightly gastric alkalinization in subjects with and without active duodenal ulcer.

Continuous 24-hour gastric pH monitoring was performed in 68 subjects to evaluate the spontaneous nightly alkalinization phenomenon (SNA). Two groups of patients were compared: the first (group A) was composed of 27 subjects with active duodenal ulcer disease; group B included 12 healthy volunteers and 29 patients with gastroesophageal reflux. Patients with duodenal disease had an alkalinization of 196.2 +/- 97.9 seconds in duration, while healthy subjects and even gastroesophageal refluxers exhibit a SNA lasting 5269 +/- 748.3 seconds (t = 6.72; p < 0.001). The absence of SNA was used as a predictive test of duodenal ulcer disease and its discriminating ability was evaluated. The evidence of this phenomenon was able to exclude the disease in 90% of group B subjects (negative predictive value) while its absence suggested correctly the presence of duodenal disease in 82% of patients (positive predictive value). The lack of SNA in duodenal ulcer patients is so frequent that its absence might be a diagnostic sign of the peptic disease.