Area Under pH 4

Abstract

Summary:Twenty‐four‐hour continuous esophageal pH monitoring has become the preferred test to quantify acid gastroesophageal reflux. Agreement has been achieved that acid gastric content reflux into the esophagus constitutes a major cause of reflux esophagitis; we therefore calculated the “area under pH 4” (A) in 560 consecutive pH monitorings in infants 1‐12 months old and related this parameter (A) to the reflux index (RI): RI < 10%: A 185 ± 295 (mean ± 1 SD); RI 10‐19%: A 1,046 ± 1,206; RI 20‐29%: A 1,967 ± 2,038; RI 30‐39%: A 3,307 ± 2,955; RI > 40%: A 7,977 ± 7,227. A higher RI is associated with a greater area under pH 4 (p < 0.001); the high SD obtained in each group, however, illustrates the great variability in surface (or acidity of the reflux episodes) in all groups. Esophagoscopy and biopsy were performed in 112 infants (20%). Specificity in the prediction of (mild) esophagitis was higher for the area under pH 4 (88%) compared with the RI (50%). The sensitivity of both parameters was comparable (96 versus 93%). Our results strongly suggest that in young infants, the acidity of the reflux episodes (the area under pH 4) is a determining factor in the prediction of esophagitis. These data need to be confirmed by more studies before general application of this parameter can be advised.