pH monitoring: is it the gold standard for the detection of gastroesophageal reflux disease?

Ambulatory, long term (24-h) intraluminal esophageal pH monitoring is the "gold standard" for detection and quantification of gastroesophageal reflux. Is it, however, the "gold standard" for the diagnosis of gastroesophageal reflux disease (GERD)? The answer depends in part on how GERD is defined. Is it to be defined on the basis of symptoms, inflammatory changes in the esophageal mucosa, extent of the exposure of the esophagus to acid or some combination of these factors? Since the correlation between acid exposure of the esophageal mucosa and either symptoms or histologic changes is poor at best, it seems there must be factors in addition to acid exposure that determine the severity of symptoms and histologic damage. One such is the resistance of the individual patient's mucosa to injury by acid exposure. In view of the above, it is not surprising that no specific value for acid exposure of the esophagus can be equated with the diagnosis of GERD. The addition of the symptom index, the frequency with which symptoms coincide with reflux episodes, has done little to increase the sensitivity and specificity of pH recording in the diagnosis of GERD. Another variable only occasionally considered is the day to day variation in the frequency and duration of acid reflux. Finally, intraesophageal pH recording measures only the intensity of acid exposure but we have no clinical measure of mucosa resistance to acid-induced injury, the other factor contributing to the pathogenesis of GERD.