There are numerous problems with pH studies; many of these problems have been alluded to in previous blog entries (see below). Another problem is that these studies are not highly predictive of response to therapy (Gut 2012; 61: 501-506).
This French study from three centers examined 100 consecutive patients (58 females) with an average age of 50 years. All patients had reflux symptoms, namely regurgitation and/or heartburn. PPI dosage was not standardized and reflux symptoms were quantified with recall questionnaires.
The authors note that up to 40% of patients with reflux symptoms have inadequate symptom relief with a 4-week course of single dose proton pump inhibitor (PPI) therapy; the aim of their study was to investigate which factors on pH probe-impedance (pH-MII) would predict a response to therapy.
Definition: Nonresponders were patients who had more than 2 days of mild symptoms per week while receiving a standard or double dose of PPI treatment for 4 weeks
- No reflux pattern on pH-MII was associated with a response to PPIs. Table 2 in the study looked at multiple factors including SI, SAP, time for acid exposure, and number of reflux events.
- Lower BMI (≤ 25 kg/m-squared), non-erosive reflux, and normal pH study were associated with poor PPI response
- Other factors associated with poor PPI response: female gender, irritable bowel syndrome (IBS), and functional dyspepsia.
- Response rates: 58% of individuals with BMI >25, 71% with esophagitis, 23% with functional dyspepsia, 30% with IBS
- Among responders, 77% were receiving a single dose PPI
Some of the poor response may be related to the study population. Only 35% had abnormal acid exposure. In total, 67% were determined to have abnormal pH studies, though this was due to a large fraction having a positive symptom-reflux association analysis.
However, this study population likely reflects a typical clinical group of patients diagnosed with GERD and demonstrates some of the shortcomings of pH-MII in clinical practice. Even patients with abnormal pH-MII studies, the presence of functional dyspepsia and IBS were strongly associated with PPI failure.
Previous related blog entries: