Multiple studies have shown that only 30-40% of patients with typical reflux symptoms (i.e., heartburn, regurgitation) have evidence of erosive esophagitis (Fig. 1) on upper endoscopy whereas the other 60-70% of patients even with troublesome reflux symptoms have no clear-cut esophageal mucosal abnormalities -. Thus, overall endoscopy is an insensitive test for diagnosing reflux disease. However, if detected, erosive esophagitis has a good positive predictive value for the diagnosis of GERD as discussed below.
A number of different classification systems for grading erosive esophagitis have been described including the Savary-Miller, Los Angeles (LA) (Table 1), Hetzel-Dent etc. -. The LA classification is a well validated, widely used system and is listed in Table 1. In general, as the grade of erosive esophagitis worsens, the degree of esophageal acid exposure increases. Lundell et al showed that the severity of esophageal acid exposure was significantly (p < 0.001)
related to the grade of esophagitis as judged by the LA classification for erosive esophagitis . Another study of 150 patients demonstrated a significantly higher duration of esophageal acid exposure in patients with grade-III/-IV esophagitis compared to grade-II esophagitis (percent time pH < 4.0 17.5% vs. 10.4%; p < 0.001). Both groups (i.e., patients with esophagitis) had significantly higher pH scores compared to control subjects (percent time pH < 4.0 1.8%; p < 0.0001) .
The presence of erosive esophagitis has a good correlation with results of 24 h pH monitoring showing increased esophageal acid exposure. In a study by DeMeester etal , the combination of typical reflux symptoms (i.e., grade-II or -III heartburn and/or regurgitation, scale of severity 0-3) and the presence of erosive esophagitis or Barrett's esophagus on en-doscopy had a 64% sensitivity and 97% specificity for accurately diagnosing GERD as defined by a positive 24-hr ambulatory pH result. A study of 24 controls and 64 patients with reflux symptoms (all of whom underwent 24-hr pH monitoring), showed that the distinction in degree of esophageal acid exposure was excellent between asymptomatic controls and patients with severe erosive esophagitis (sensitivity and specificity both 100% by logistic regression) but discrimination was relatively poor when asymptomatic controls were compared to symptomatic patients without esophagitis (71% and 79% by logistic regression) .
On the other hand, a study from Spain showed that 34% of patients with grade-I and -II esophagitis showed variable patterns of reflux whereas most patients (76.2%) with grade-III and -IV esophagitis showed a clearly defined pattern of gastroesophageal reflux in both the supine and the upright positions (p < 0.05)
Table 1. The Los Angeles Classification System for the endoscopic assessment of grade of esophagitis 
(A) One or more mucosal breaks no longer than 5 mm, none of which extends between the tops of the mucosal folds
(B) One or more mucosal breaks more than 5 mm long, none of which extends between the tops of two mucosal folds
(c) Mucosal breaks that extend between the tops of two or more mucosal folds, but which involve less than 75% of the oesophageal circumference (D) Mucosal breaks which involve at least 75% of the oesophageal circumference
. In another study of 100 patients with reflux symptoms, 51% and 48% of patients respectively with grades 1 and 2 esophagitis had a normal DeMeester's score (< 14.7) . This raises questions whether milder grades of esophagitis on endoscopy may overdiagnose GERD, if other causes of esophagitis may have been present and last but not the least, if results of 24-hr pH monitoring may have been falsely negative. Furthermore, some patients may be susceptible to esopha-geal damage at relatively low levels of acid exposure.
All these studies have compared endoscopic findings to 24-h ambulatory pH - using it as the gold standard, which is less than a perfect test for the diagnosis of GERD. Studies have shown that 37-60% of patients with non erosive reflux disease (NERD), as defined either by symptom response to PPI or significant symptom correlation with reflux episodes, will have normal ambulatory 24-H esophageal pH results , , , . Moreover, when the reproducibility of prolonged esophageal pH testing is measured on two separate days in patients with reflux symptoms or with esophagitis, the results change the diagnosis (normal or abnormal based on the percentage time pH < 4.0) in 11% of the cases . Thus, comparison with 24-h pH monitoring may lower the sensitivity of milder forms of erosive esophagitis in the diagnosis of GERD. It is possible that these shortcomings may be overcome by using the new Bravo wireless pH device and correlating these pH results to the presence of erosive esopha-gitis. Results of such studies are as yet awaited.
Overall, in the presence of typical reflux symptoms (i.e. heartburn), detection of macroscopic endoscopic injury is strongly predictive of the diagnosis of GERD.
Given the lack of efficacy of non-drug measures and antacids and the relatively low efficacy of H2 receptor antagonists, the majority of patients with erosive esophagitis require acid suppression therapy using PPI's (proton pump inhibitors) . Also, patients with erosive esophagitis, especially those with higher grades are less likely to be effectively managed with less than standard dose of PPI therapy, and step-down attempts in this group are less successful . Castell etal  noted in a large study (n = 5,241) declining efficacy of PPI's in patients with more severe grades of esophagitis (healing at 8 weeks- 92-94% in grades A/B compared to 70-72% in grades C/D).
Multiple studies have also shown that the presence of erosive esophagitis at baseline is predictive of the need for chronic acid suppression , . A long term follow up study (> 3 years) in elderly patients (> 65 years) with documented esophagitis as a inclusion criterion suggested that the presence of severe grades of esophagitis at baseline (p = 0.009) was a risk factor for relapse of esophagitis, suggesting need for maintenance therapy in this group of patients .
Thus, it is clear that more severe grades of esophagitis require more complete acid suppression for intial healing as well as for maintenance of healing . However, GERD is a symptom driven disorder and this information may not be necessary to guide therapy in all patients .
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Gastroesophageal reflux disease is the medical term for what we know as acid reflux. Acid reflux occurs when the stomach releases its liquid back into the esophagus, causing inflammation and damage to the esophageal lining. The regurgitated acid most often consists of a few compoundsbr acid, bile, and pepsin.