Is there a relationship between the pH and volume of saliva and esophageal pH-metry results?

There are several implications in the buffer capacity and in the protective role of saliva in gastroesophageal reflux disease (GERD) and other digestive disorders. The lack of knowledge about the production and quality of saliva and the fact that saliva plays an important role in digestive homeostasis motivated the authors to study the relationship between reflux measured by esophageal pH-metry and the pH and volume of saliva in individuals with GERD and its laryngopharyngeal manifestations (LPR). The study was designed as a randomized clinical trial. The studied population consisted of 39 adults with GERD and LPR confirmed by a positive 24-hour double-probe esophageal pH-metry. Unstimulated whole saliva was collected and its pH and volume were compared to pH-metry results. Patients were divided into four groups according to the number of distal episodes of reflux and two groups according to the presence or absence of proximal reflux. A highly significant difference was found between the groups with distal reflux when comparing salivary volume alone and salivary volume/salivary pH. The same occurred for the presence or absence of proximal reflux. These results suggest a direct correlation between salivary volume and "salivary pH x volume" with the number of distal and proximal episodes of reflux on the esophageal pH-metry. If larger studies confirm this finding, in the future it might be possible to diagnose GERD and LPR through a simple "spit test," avoiding more costly and invasive procedures.