THE UTILITY OF SYMPTOM ASSOCIATION PROBABILITY (SAP) DURING IMPEDANCE-PH MONITORING IN PREDICTING OUTCOME AFTER ANTIREFLUX SURGERY FOR LARYNGOPHARYNGEAL REFLUX

Introduction: Symptom association probability (SAP) is an index that determines if there is a statistical association between symptoms and reflux episodes on pH-monitoring or multichannel intraluminal impedance-pH monitoring (MII-pH). Studies have questioned the value of SAP during pH monitoring in predicting outcomes after anti-reflux surgery (ARS) in patients with typical reflux symptoms. However, there is a paucity of data on the value of MII-pH SAP in predicting ARS outcomes in patients with laryngopharyngeal reflux (LPR). The aim of this study was to assess the utility of SAP in predicting ARS outcomes for patients with LPR.

Methods: Records of patients who underwent primary Nissen fundoplication or magnetic sphincter augmentation (MSA) for LPR at our institution from 2013 to 2021 were reviewed. Patients with predominant LPR symptoms, a reflux symptom index (RSI) score >13, and a documented SAP for up to 3 symptoms on MII-pH were included. A symptom with SAP >95% was considered positive (SAP+), indicating a statistically significant association between that symptom and reflux events. Favorable outcome was defined as freedom from PPIs, primary symptom resolution, and a 5-point decrease or RSI score ≤13. The presence and number of SAP+ symptoms, as well as SAP+ for typical and atypical reflux symptoms were evaluated for an association with surgical outcomes. Sub analyses of SAP for acid and non-acid reflux episodes were performed.

Results: The final study population consisted of 212 patients (76.4% female) with a median (IQR) age of 60(49-67) and BMI of 28.0(25-31). On MII-pH patients had 1(0-3) LPR events and 11(6-20) full column reflux events. Nissen fundoplication was performed in 93(43.9%) patients and 119 underwent MSA. Age, sex, BMI, MII-pH parameters were similar between surgery types (p>0.05). At a mean(SD) follow-up of 13(4.8) months the RSI score improved from 28(22-35) to 9(4-17), (p<0.001) and 81.1% of patients achieved favorable outcome.
SAP was positive in 63.7% of patients. There was no association between having at least one SAP+ symptom and outcome (p=1.000). Outcome was similar between patients with one, two or all SAP+ symptoms (p=0.791). No association with outcome was found with SAP+ typical or atypical symptoms (p>0.05). Similar results were found in the sub analyses for SAP for acid (p=0.861) and non-acid reflux episodes (p=0.102). Subgroups based on age, sex, and BMI also showed no relationship between SAP and outcome (p>0.05). Similarly, there was no relationship between SAP and outcome in surgery type subgroups (p>0.05).

Conclusion: Symptom association probability was not associated with outcomes after antireflux surgery for LPR. These findings suggest that presence of symptoms should be assessed independently of their association with reflux events for risk stratification and expectation management.