Symptom-associated probability does not reliably distinguish functional heartburn from reflux hypersensitivity

Summary

Background

Symptom association probability (SAP) is thought to distinguish reflux hypersensitivity from functional disorders. A diagnosis of hypersensitive oesophagus (SAP-positive) indicates that gastro-oesophageal reflux disease (GERD) is the cause of continued symptoms.

Aim

To conduct an analysis of pH and symptom criteria that lead to a diagnosis of SAP-positivity

Methods

We calculated SAP for 205 patients with GERD symptoms refractory to proton pump inhibitor (PPI) therapy who underwent endoscopy with wireless pH monitoring from 2007 to 2014. Patients were divided into three groups: pH-negative with no oesophagitis (n = 45), pH-positive with no oesophagitis (n = 130), and patients with oesophagitis (n = 30). We constructed a 2 × 2 table of symptom and reflux event association and quantified the number of 2-minute intervals for each of the 2 × 2 variables that distinguished SAP-positive from SAP-negative. In a separate cohort of 58 patients who had undergone anti-reflux surgery, we evaluated the effects of pre-surgery SAP.

Results

The difference in symptom association parameters that led to a diagnosis of an SAP-positive was small (2.98% in oesophagitis-positive; 1.56% in oesophagitis-negative/pH-positive; 0.48% in oesophagitis-negative/pH-negative). In the pH-negative/oesophagitis-negative group, a difference of 0.48% led to a diagnosis of hypersensitivity. There was significant variability in SAP values between day 1 and day 2 of pH testing in all groups, with the greatest in the oesophagitis-positive group, despite objective evidence for reflux (27% in oesophagitis-positive, 19% pH-positive/oesophagitis-negative, and 7% in pH-negative/oesophagitis-negative). Pre-surgery SAP was not associated with response to anti-reflux surgery.

Conclusion

In PPI-refractory GERD, SAP cannot accurately distinguish reflux hypersensitivity from functional oesophageal symptoms.

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