Does fasting serum gastrin predict gastric acid suppression in patients onproton-pump inhibitors?

Proton pump inhibitors (PPIs) block gastric acid secretion and may increase serum gastrin concentration. The aim of this study was to determine whethe r fasting serum gastrin concentration predicts gastric acid suppression in patients on PPI therapy. Ambulatory pH monitoring with one pH probe in the distal esophagus and a second probe in the stomach was performed in patient s with persistent symptoms of GERD despite PPI treatment. Upon completion o f pH monitoring, blood was drawn for measurement of fasting serum gastrin c oncentration. In all, 51 patients were studied: 26 on PPIs, 1 on H-2-recept or antagonists, and 24 off acid suppression. Fasting serum gastrin correlat ed inversely with percent time of gastric pH < 4 for all patients (r = -0.5 53; P < 0.001) and for the subgroup of 26 patients on PPIs (r = -0.435; P = 0.027). In patients on PPIs, an elevated gastrin (greater than or equal to 100 pg/ml) was associated with gastric pH < 4 for 25 +/- 7% of the time co mpared to 54 +/- 5% when the gastrin was normal (P = 0.004). Therapeutic ga stric acid suppression (gastric pH < 4 for <50% of time) was present in 6 o f 7 (86%) patients with an elevated fasting serum gastrin, compared with on ly 8 of 19 (42%) patients with a normal serum gastrin (P < 0.05). In conclu sion, there is a significant inverse correlation between the fasting serum gastrin concentration and gastric acid profile in patients with GERD. An el evated fasting serum gastrin concentration while on PPI therapy suggests th at gastric acid secretion is adequately suppressed.