Best method to diagnose GERD is
24 hours oesophageal pH monitoring is the gold standard investigation. PPI should be stopped for 3 weeks prior to pH monitoring. Dual probe pH monitoring(one in distal oesophagus and one in proximal oesophagus) is used to confirm the respiratory complication of GERD. Reference: SRB's Manual of Surgery, 6th Edition, page no= 782.
Oesophageal pH determination
Endoscopy
Barium swallow
Laparoscopy
G.I.T