Comment on: Diagnostic accuracy of mean nocturnal basal impedance and other complementary tests for the diagnosis of gastroesophageal reflux disease according to the new Lyon criteria

Dear Editors,

We read with great interest the article “Diagnostic accuracy of mean nocturnal basal impedance and other complementary tests for the diagnosis of GERD according to the new Lyon criteria” by Lombo-Moreno et al. ¹ The authors provided valuable data on the performance of Mean Nocturnal Basal Impedance (MNBI) and related impedance-pH indices in light of the 2024 updated diagnostic framework.^2,3 Their findings, particularly the suboptimal discriminatory ability of MNBI, contribute meaningfully to a rapidly evolving field. However, a few aspects require further discussion.

First, the authors’ observation that MNBI discriminates GERD only modestly (AUC 0.77) is consistent with evidence showing considerable regional variability in normative impedance values. ⁴ The international consensus analysis by Sifrim et al. demonstrated substantial inter-center differences in impedance-pH metrics, even among healthy subjects, raising important concerns about the universal applicability of fixed MNBI cutoffs. Their work strongly supports the authors’ argument that MNBI should be interpreted within a broader clinical–physiological context rather than as a stand-alone diagnostic discriminator.

Second, the study emphasizes that many patients reporting typical esophageal symptoms and labeled as GERD are better explained by reflux hypersensitivity, functional heartburn, or behavioral factors rather than ongoing pathologic reflux. ⁵ In this light, the suboptimal performance of adjunctive objective metrics—MNBI, bolus exposure, or total reflux episodes—reinforces the need for integrated diagnostic reasoning rather than reliance on isolated numerical thresholds. Indeed, many studies emphasized the role of clinical parameters combined with pathophysiological findings in characterizing patients with foregut symptoms.^6,7

Finally, the better diagnostic performance of the DeMeester score observed in this study is intriguing, but should be viewed in the context that the definition of GERD was based on erosive esophagitis (grade B, C, and D erosive esophagitis) and abnormal esophageal acid exposure (>6% over 24 h), findings which are mostly affected by the acidity of the refluxate, similarly to the DeMeester score. The present findings of low sensitivity and specificity across multiple impedance-pH adjunctive measures are therefore not surprising; such physiologic abnormalities may not correlate directly with acid exposure or bolus transit indices despite remaining clinically relevant contributors to esophageal symptoms. ⁸

Overall, this work appropriately underscores both the promise and limitations of complementary impedance-derived metrics within the updated Lyon 2.0 diagnostic structure. However, the limitations of the study—particularly the retrospective design, relatively small sample size, and potential timing mismatches between endoscopy and pH monitoring—limit the robustness and generalizability of the data. Further prospective, multicenter studies, incorporating regional impedance normal data and phenotype-specific analyses, are needed to refine the diagnostic utility of these metrics within the Lyon 2.0 framework.