With this test, a small wire with an acid sensor is placed through the infant’s nose down to the bottom of the esophagus. The sensor is usually left in place for 12-24 hours. It can detect when stomach acid “refluxes” into the esophagus. This information is generally recorded on a computer. At the conclusion of the test, we can determine how often the infant “refluxes” and whether there are any symptoms when this occurs.
Unfortunately, the severity of reflux as measured by pH probe often doesn’t correlate with the severity of symptoms . . . that is, some infants with very frequent vomiting will have a normal pH probe study. Perhaps more important, the severity of reflux measured by a pH probe does not help to predict the ultimate outcome. Although pH probe analysis is abnormal in nearly 80% of infants with mild reflux symptoms (i.e. occasional spitting and vomiting), one third of infants with severe symptoms have a normal pH probe study! Also, fewer than 40% of infants with severe esophagitis due to chronic reflux will have abnormal pH probe studies.
Perhaps the greatest potential value of pH probe analysis is in trying to correlate reflux with unusual or persistent symptoms such as apnea, stridor, coughing or wheezing, choking, gagging, or unexplained irritability. If these symptoms occur frequently enough, a pH probe analysis can determine if these symptoms occur at the same time as episodes of acid reflux.