A modification of the quininium resin test for assessing gastric acidity

Background: Gastric acid is an important defence against enteric infection. Studies investigating the relationship between hypochlorhydria and enteric infections or gastric malignancy have been limited by difficulties in the non-invasive measurement of gastric acidity. Aim: To develop a blood test for hypochlorhydria based on the quininium rosin test. Methods: Quininium resin dissociates to liberate free quinine at pH less than or equal to 3.5. Ten fasting adult volunteers ingested 100 mg/kg of quininium resin twice: once before (control) and once after acid suppression with rabeprazole (10 mg b.d. for 3 days). Blood and serum samples were collected at baseline and 45, 60, 75, 90 and 120 min after ingestion. Quinine levels were measured fluorometrically from 100 muL samples after simple extraction. Results obtained by the quininium resin test were compared with gastric juice pH measurements. Results: After quininium resin ingestion, mean quinine levels were lower in the acid-suppressed than in the control condition at all times (P < 0.001). Optimized cut-off values at 90 min post-ingestion yielded 95% accuracy rates in both serum and blood. Quininium resin was well tolerated. Conclusions: Using blood or serum, the quininium resin test identifies hypochlorhydria accurately and non-invasively. This test may be useful in screening for gastric atrophy and in studies investigating hypochlorhydria.