Comparison of the serial dilution indicator and intragastric titration methods for measurement of meal-stimulated gastric acid secretion in man.

Two in vivo methods that permit quantitation of gastric acid secretion immediately after the meal are currently in use: intragastric titration and the serial dilution indicator method. During intragastric titration, intragastric pH is artificially maintained at 5.5 to 7 by the continuous addition of alkali to the gastric contents, while during serial dilution the intragastric pH is permitted to seek its natural pH. This study compared gastric acid secretion and serum gastrin in response to a liquid protein meal measured by both techniques in 10 subjects. Mean (+/- SE) 3-hr acid outputs were almost identical (53.6 +/- 6.0 mmol/3 hr with intragastric titration and 52.0 +/- 8.5 mmol/3 hr with serial dilution indicator). Furthermore, 30 min secretory responses in individual subjects were highly correlated (r = 0.98 +/- 0.01, P less than 0.001). Also, in spite of intragastric pH being less than 1.5 by 90 min after the meal during the serial dilution method, total integrated serum gastrin concentrations after the meal were similar (intragastric titration = 20.6 +/- 7.3 ng min/ml versus serial dilution indicator = 23.5 +/- 9.8 ng min/ml) and individual 30-min gastrins during the two separate tests were highly correlated (r = 0.80 +/- 0.06, P less than 0.01). It is concluded that both meal-stimulated gastric acid secretion and serum gastrin concentrations as measured by intragastric titration and by the serial dilution indicator method produced similar results.