Which of the following is the gold standard test for Laryngopharyngeal Reflux?

Currently, the Gold standard test for Laryngopharyngeal Reflux is 24 hour double probe pH monitoring. An arbitrary threshold of pH=4 is used to diagnose reflux whether at the esophageal probe (5 cm above the lower esophageal sphincter) for gastroesophageal reflux or at the pharyngeal probe (2 cm above the upper esophageal sphincter) for laryngopharyngeal reflux (LPR).