Final answer:
The esophageal acid reflux test is used to diagnose GERD in patients with noncardiac chest pain.
Step-by-step explanation:
The purpose of the esophageal acid reflux test in patients with noncardiac chest pain is to diagnose gastroesophageal reflux disease (GERD). This test helps to determine if the chest pain is caused by the backflow of stomach acid into the esophagus. The test measures the amount and severity of acid reflux, and can help guide treatment decisions for noncardiac chest pain.