FLIP Panometry Tops HRM for Esophageal Motility Measurement

Heidi Splete

September 17, 2021

Functional luminal imaging probe (FLIP) panometry proved superior to high-resolution manometry (HRM) for evaluation of esophageal motility, according to a new study based on data from 329 adults.

HRM is generally considered the primary method for evaluating esophageal motility, but current recommendations include the use of a FLIP or timed barium esophogram (TBE) if HRM yields inconclusive results, Dustin A. Carlson, MD, of Northwestern University, Chicago, and colleagues wrote in the recent study. FLIP has several potential advantages over HRM, including that "the test is performed on a sedated patient at the time of endoscopy, as opposed to the awake transnasal catheter used for HRM"; however, comparisons of the two methods for predicting esophageal retention are lacking.

In the study published in the American Journal of Gastroenterology, the researchers reviewed data from 329 consecutive patients aged 18-89 years who completed FLIP, HRM, and TBE for evaluation of primary esophageal motility. They excluded patients with previous foregut surgery. The researchers compared the ability of FLIP and HRM to predict esophageal retention based on abnormal TBE findings, which was defined as a 1-minute column height greater than 5 cm or as impaction of a 12.5-mm barium tablet.

For HRM, the integrated relaxation pressure (IRP) was assessed in the supine and upright patient positions to predict abnormal TBE findings. For FLIP, esophagogastric junction (EGJ) opening was assessed with a 16-cm FLIP performed during sedated endoscopy, and the presence of abnormal TBE findings was determined using the EGJ–distensibility index and maximum EGJ diameter.

The area under the ROC curve for identifying abnormal TBE findings was 0.79 (95% confidence interval, 0.75-0.84) for supine, 0.79 (95% CI, 0.76-0.86) for upright IRP, 0.84 (95% CI, 0.79-0.88) for the EGJ–distensibility index, and 0.88 (95% CI, 0.85-0.92) for the maximum EGJ diameter.

In a logistic regression analysis, the odds ratios for predicting abnormal TBE findings were 1.8 (95% confidence interval, 0.84-3.7; P < .133) for consistent elevation of IRP in HRM, compared with normal IRP, and 39.7 (95% CI, 16.4-96.2; P < .001) for reduced EGJ opening on FLIP panometry, compared with normal EGJ opening.

"Both the IRP on HRM and FLIP panometry metrics of EGJ opening (EGJ–[distensibility index] and maximum EGJ diameter) demonstrated capabilities to differentiate between abnormal and normal esophageal retention, which supports confidence in both tools," the authors explained. "However, FLIP panometry parameters did so more accurately and with greater predictive capability as reflected by ROC and regression analysis."

A total of 40 patients (12%) showed discordance between their HRM and FLIP panometry measures, and among these, FLIP showed stronger detection of esophageal retention. FLIP panometry was consistent with TBE in 78% of cases, while HRM-IRP was consistent with TBE in 23%. "Discordant results between HRM and FLIP panometry were observed in previous studies and again in this study, a scenario with unclear clinical significance," the authors noted, which was why they used TBE as "an objective measure of esophageal retention that was independent of both HRM and FLIP to compare the two modalities."

The study findings were limited by several factors including ones related to the use of TBE as the primary outcome, as well as the lack of longitudinal outcomes, the researchers noted. There is also the potential for referral bias and selection bias with an overrepresentation of patients with achalasia and EGJ outflow obstruction. However, the results were strengthened by the large sample size of patients who completed evaluations with HRM, FLIP, and TBE.

The study "provides additional support for the use of FLIP panometry to evaluate esophageal motility because it accurately identifies normal and abnormal retention, but also identifies patients who should undergo further complementary diagnostic testing," they noted. Longitudinal studies are needed to explore best practices for managing esophageal motor disorders. In the meantime, evaluation with FLIP panometry, TBE, and HRM likely remains necessary for some patients, "particularly those with equivocal findings on a single test," to better characterize disease and guide treatment, the researchers concluded.

Findings Support Potential of FLIP

"The endoscopic FLIP is an exciting clinical tool that utilizes distension of a catheter-mounted balloon to different volumes to acquire esophageal dimensions and pressures," Amit Patel, MD, of Duke University, Durham, N.C., said in an interview.

Dr Amit Patel

"Accumulating data on FLIP inspired the recently published ACG Clinical Guidelines: Esophageal Physiologic Testing to suggest the use of FLIP to complement high-resolution manometry in the setting of obstructive esophageal symptoms and borderline HRM findings, for patients in whom an HRM study cannot be completed, and for intraprocedural use during interventions for achalasia," Patel said. "However, the comparative utility of FLIP, particularly among foundational esophageal diagnostics such as HRM and TBE, is less well developed at this point."

Patel said he was surprised by some of the findings. "The characteristics of FLIP metrics (specifically, EGJ–distensibility index <2 mm2/mm Hg and/or maximum EGJ diameter <12 mm) were numerically superior to those for traditional IRP metrics from HRM in predicting retention on TBE on AUROC, regression analyses, and discordant cases in this study," said Patel. "Although this study also corroborated the value of IRP on HRM, these findings were somewhat surprising for HRM, given its well-earned reputation as the gold standard for the diagnosis of esophageal motor disorders, its widespread use, and the record of strong data supporting its important role in clinical practice."

Overall, this study suggests these metrics from FLIP (namely, EGJ–distensibility index and EGJ diameter) may have "diagnostic value beyond traditional IRP metrics from HRM to identify objective retention on TBE," said Patel, who also said these exciting findings "support the growth of the complementary role of FLIP ... particularly in cases where HRM may be inconclusive or not tolerated by patients."

However, more research is needed. "Taking into account other HRM metrics beyond IRP, such as intrabolus pressures or evaluation of bolus transit on impedance, and provocative maneuvers on HRM, such as rapid drink challenges or solid swallows, may be appropriate for further evaluation, as will improved arbitration of 'borderline' metrics or less clear cases," Patel emphasized. Future studies should also incorporate management interventions and assessments of outcomes.

The study was supported by a grant from the Public Health service to a coinvestigator, and by the American College of Gastroenterology Junior Faculty Development Award to lead author Carlson. Carlson also disclosed speaking and consulting relationships with Medtronic, which manufactures FLIP panometry systems. Northwestern University and several coauthors also disclosed intellectual property rights and ownership surrounding FLIP panometry systems, methods, and apparatus with Medtronic. Patel had no financial conflicts to disclose.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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