Original article—alimentary tract
Caution About Overinterpretation of Symptom Indexes in Reflux Monitoring for Refractory Gastroesophageal Reflux Disease

https://doi.org/10.1016/j.cgh.2011.07.009Get rights and content

Background & Aims

Symptom index (SI) and symptom association probability (SAP) are indexes used to analyze data collected from ambulatory pH and/or impedance monitoring and quantify the association between symptoms and reflux events. However, their characteristics are not well defined. We measured factors that affect SI and SAP values to determine their utility in assessing patients with refractory gastroesophageal reflux disease (GERD).

Methods

We conducted a cross-sectional study of 254 patients with poor responses to proton pump inhibitor (PPI) therapy. Participants underwent esophagogastroduodenoscopy and wireless pH (n = 127) or impedance/pH monitoring when they were not receiving PPI therapy (n = 41) or impedance/pH monitoring while they received twice-daily PPI therapy (n = 86). SI and SAP values were calculated individually; ranges of values for each cell in the 2 × 2 contingency table were determined. Monte Carlo simulation was conducted to determine how varying reflux and symptom rates within the contingency table impacted the expected value and variability in SI and SAP.

Results

At best, only 33% of patients who were refractory to PPI therapy had positive SI or SAP scores for acid or nonacid reflux events. Abnormal SAP (>95%) and SI (>50%) scores required high rates of reflux. At reflux rates less than 10%, observed in 70% of the studied population, SI and SAP values were largely determined by chance occurrences, rather than the relationship between symptoms and reflux. The values for each index varied significantly day-to-day.

Conclusions

SI or SAP indexes can be overinterpreted, unless patients with gastroesophageal reflux disease who are refractory to PPI therapy have high rates of reflux.

Section snippets

Methods

The study was performed in accordance with the Declaration of Helsinki, good clinical practice, and applicable regulatory requirements. The Vanderbilt Institutional Review Board approved this clinical trial (IRB#101110) (NCT01204931).

Demographics

Two hundred fifty-four patients underwent: (1) esophagogastroduodenoscopy with wireless pH monitoring off PPI therapy (n = 127), (2) impedance/pH monitoring off PPI therapy (n = 41), or (3) impedance/pH monitoring on BID PPI therapy (n = 86) (Table 1). The primary and mutually exclusive symptom complaints included cough, heartburn, regurgitation, and chest pain. Esophagitis (LA grades of esophagitis: A = 50%, B = 27%; C = 16%, and D = 7%) was present in 15/127 (12%) patients who underwent

Discussion

This study is the first to critically assess the clinical utility of SI and SAP in patients with symptoms refractory to PPI therapy and to determine test characteristics which impact both indexes. Our data and findings are derived from all possible clinically relevant modes of therapy (off vs on therapy) and reflux monitoring methods (acid, nonacid, and total reflux events) with overwhelming implications. We found that the likelihood of abnormal SI and SAP in this group of patients is low and

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    Conflicts of interest This author discloses the following: Dr Vaezi had research grant support from Takeda Pharmaceuticals North America, Inc, for the conduct of this study. The remaining authors disclose no conflicts.

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