24-Hour Esophageal pH Study is used to measure the number of the reflux episodes during a person’s day, when endoscopy (EGD) findings are normal. This test determines the severity of gastroesophageal reflux disease (GERD) and measures the amount of time stomach acid is present in the esophagus. A benefit is that it allows for the evaluation of a patient’s symptoms with activity, at home or work and especially during sleep. Study results will show if reflux is the cause of non-cardiac chest pain, hoarseness, coughing, halitosis or asthma. This information will assist your physician in planning your treatment.