Symptom association latency during ambulatory reflux monitoring: a review of 1445 symptoms

To determine the optimal time window of symptom association in GERD patient, a 2-minute time window is nonapplicable for all gastroesophageal reflux (GERD) symptoms and 5 minutes remains an arbitrary choice. Symptom association analysis is a critical component in pH-impedance (imp) testing. Symptom index (SI) and symptom association probability (SAP) are the two widely accepted methods. Both were introduced in the preimpedance era and initially tested in patients with typical GERD symptoms. We reviewed ambulatory pH-imp studies of (294) patients referred for evaluation of possible GERD symptoms from January 2012 to August 2015. Patients with heartburn (HB), regurgitation (Reg), cough, and throat clearing (TC) alone or in combination were reviewed. The analysis time windows were separated into five intervals (0-1, 1-2, 2-3, 3-4, 4-5 minutes) to explore the frequency of symptom occurrence in each window. The SI was then calculated and contrasted to the usual 5-minute window; similar calculations were made to SAP 2-minute windows. Secondary analysis was performed to test whether symptoms due to acid reflux have a different time perception than non-acid. Overall, there were 1445 total symptoms preceded by impedance detected reflux. Frequency analysis showed that (34.7%- 86.7%) of symptoms occurred in the first minute after onset of the reflux. χ2 showed a significant association between SI with 1 minute and SAP for heartburn (P ≤ 0.0001) and regurgitation (P = 0.0003). There was also a significant association between cough with 2-minute window and SAP (P = 0.025). There was no significant association between TC at 1-, 2-, 3-, and 4-minute time windows and SAP. There was no evidence of increased frequency of positive reflux to symptoms over time. There was also no significant difference in time window in relation to acid or nonacid reflux. It seems doubtful that a universal time window can be applied to all GERD symptoms to calculate symptom association.