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Trajectory of pH monitoring helps characterize patients non-responsive to PPIs
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CHICAGO — Trajectory analysis of wireless pH monitoring can help guide diagnosis and management of patients with GERD who do not respond to PPIs and have variable esophageal acid exposure over time, according to research presented at Digestive Disease Week.
“Wireless pH monitoring has benefits compared to conventional catheter-based systems, which include an increased tolerability, improved sensitivity of reflux detection and prolonged monitoring capability, up to 96 hours. Yet despite these known benefits, in the clinical setting we do face diagnostic challenges with wireless monitoring,” Rena Hiren Yadlapati, MD, MS, of Northwestern University Feinberg School of Medicine, said during her presentation. “For one, esophageal acid exposure can vary day-to-day among the patient. Yet when we interpret these studies, we decide whether they’re abnormal or normal based on the number of positive days [and] the clinical relevance of these findings is often unclear and managed heterogeneously.”
Without a clear method to discern normal from abnormal acid exposure, Yadlapati and colleagues hypothesized that accounting for the variability in acid exposure to assess patterns of acid exposure time (AET) may have diagnostic value.
They retrospectively evaluated the acid exposure patterns of 212 PPI non-responders who underwent prolonged wireless pH monitoring after discontinuing PPI therapy at Northwestern University between August 2010 and September 2016 (65% women; 69% white; mean age; 46.7 years).
Factors related to the protocol, such as time of capsule placement and weekend monitoring, did not affect acid exposure. However, regurgitation (OR = 1.9; 95% CI, 1.2-3.2) and hiatal hernia size exceeding 2 cm (OR = 13.1) were linked to higher acid exposure, while cough only was “interestingly” linked to lower acid exposure, but this did not reach statistical significance, Yadlapati said.
A “positive” acid exposure day was defined as a pH below 4 for more than 5% of the time. Overall, 44% of patients had no positive days, 18% had one, 14% had two and 24% had three or more.
The investigators observed significant variability in esophageal acid exposure day-to-day, with particularly higher acid exposure on day 1 compared with days 2 and 4 (P < .01 for both comparisons).
“Interestingly, daily AET varied the most for subjects who were in the 1-day positive and 2-day positive groups,” Yadlapati said.
Next, the researchers used group based trajectory modeling, “a statistical model that identified groups of similar longitudinal patterns without considering a predetermined threshold,” to analyze patterns of acid exposure over time.
Analyzing the trajectory of acid exposure over 4 days showed that patients could be characterized into three distinct esophageal acid exposure patterns: low (64% with a median AET of 1.5), moderate (28% with a median AET of 7.2) and high esophageal acid exposure trajectories (8% with a median AET of 13). Grouping based on trajectory showed significant agreement with grouping based on days positive (P < .0001).
“The trajectory model was highly significant, suggesting there was significant stability within each group and that there was significant difference between the three groups,” Yadlapati said.
“Trajectory modeling increased our confidence that those with 0-day positive and those with 3- or more days positive reliably represent normal or abnormal burden, but it didn’t quite offer any novel information. Where trajectory modeling seemed to be most helpful was for the middle group, the 1-day positive and 2-day positive studies.”
The model showed 31% of 2-day positive patients had a low acid exposure trajectory, though they are usually considered abnormal, she said. Further, 15% of the 1-day positive patents had a moderate acid exposure trajectory and 85% had a low trajectory.
The added perspective of trajectory modeling may help confirm patients who do not have elevated acid exposure, for whom PPI discontinuation and seeking different etiologies of their symptoms can be considered, and those who do have elevated acid exposure, for whom optimization of acid suppression and further reflux testing can be considered.
Finally, the investigators observed 3-day trajectory analysis resulted in comparable grouping to 4-day trajectory analysis (P < .0001), suggesting that 4 days of monitoring may be unnecessary.
“Importantly, trajectory modeling provides a new perspective on acid exposure burden within the middle, difficult to interpret groups,” Yadlapati concluded. “This exploratory analysis is hypothesis generating. It suggests that a secondary assessment of patterns of acid exposure over time may help to guide diagnosis and management, particularly for cases that are unclear based on number of days positive.” – by Adam Leitenberger
Reference:
Yadlapati RH, et al. Abstract 8. Presented at: Digestive Disease Week; May 6-9, 2017; Chicago.
Disclosures: Yadlapati reports no relevant financial disclosures.
Editor’s note: This headline has been changed to better reflect the patient population.