We thank Dr. Koulaouzidis and Dr. Toth for their thoughtful comments regarding our study evaluating whether antroduodenal contractile parameters measured by wireless motility capsule (WMC) may predict response to gastric per-oral endoscopic myotomy (G-POEM) in refractory gastroparesis. Several of the methodologic issues raised relate to the exploratory nature of our analysis. As we discussed in our paper, this was a retrospective cohort study of modest size, and subgroup analyses should be interpreted with caution. We agree that our findings should be viewed as hypothesis-generating rather than actively guiding clinical practice and that these findings require validation in future prospective studies. While WMC does not capture detailed spatial propagation patterns, WMC-derived pressure measurements remain a useful biomarker of contractile activity. Prior studies have demonstrated significant differences in WMC antroduodenal contractility between gastroparesis patients and healthy controls. We applied these previously validated thresholds to allow clinically meaningful stratification in our smaller cohort and elected not to derive thresholds from our own dataset to avoid overfitting and inflation of predictive performance. Our study was also not designed to internally validate the contractility thresholds as it did not include healthy controls. The influence of comorbid major psychiatric disease on treatment response is an important consideration. The observed association of major psychiatric disease with G-POEM non-response is plausible given the motor and sensory neuroenteric underpinnings of gastroparesis symptoms. However, multivariate modeling that would adjust for confounders risks overfitting and is statistically unstable given the limited number of outcome events. Thus, we elected to present univariable analyses and interpret the results cautiously. Larger prospective cohorts will be necessary to determine whether WMC-derived contractility parameters remain independently predictive after accounting for relevant clinical variables. As noted in our manuscript, a functionally equivalent capsule (AnX MotiliCap) is now commercially available as a successor to the SmartPill WMC system. We agree that cross-platform validation is necessary before applying these findings to newer systems. However, our findings highlight an opportunity to evaluate similar contractile biomarkers using emerging capsule technologies in future studies. The future of managing gastroparesis will rest on improved physiologic phenotyping through tools such as functional lumen impedance planimetry, body surface gastric mapping, and antroduodenal manometry. The role of WMC, as a widely available and non-invasive test, warrants further investigation in this context. Sincerely, Kevin Huang, Brian Surjanhata, Annie Zhu, Ingrid Guerrero-Lopez, Braden Kuo, and Michael Cline All authors contributed to drafting and revising the manuscript and approved the final version. The authors declare no conflicts of interest. This article is linked to Huang et al. and Koulaouzidis et al. papers. To view these articles, visit https://doi.org/10.1111/nmo.70276 and https://doi.org/10.1111/nmo.70296. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
Huang et al. (Wed,) studied this question.