Validity of the Cutoff Value for Integrated Relaxation Pressure Used in the Starlet High-Resolution Manometry System

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Background: In a previous study that used the Starlet high-resolution manometry system to assess integrated relaxation pressure (IRP) in healthy adults, the predicted cutoff value was about 26 mm Hg. However, some patients with achalasia have an IRP value of <26 mm Hg. This study examined the validity of the Starlet IRP cutoff value in patients with achalasia. Methods: Among 37 patients with achalasia, the percentage of patients with a Starlet IRP value ≥26 mm Hg was calculated. Patients were then classified as IRP-high (IRP ≥26 mm Hg) and IRP-low (IRP <26 mm Hg), and the groups were compared in relation to basal lower esophageal sphincter (LES) pressure, Chicago classification achalasia subtype, and esophagography subtype. Results: Twenty (54%) of the 37 patients had an IRP of ≥26 mm Hg. Basal LES pressure was significantly higher in the IRP-high group than in the IRP-low group. Chicago classification Type II achalasia was most common in the IRP-high group, whereas Type I was most common in the IRP-low group. No significant difference was noted in the distribution of esophagography subtypes between groups. Conclusions: It is difficult to determine an IRP cutoff value with Starlet. When diagnosing achalasia with Starlet, comprehensive assessment must consider findings other than IRP values. In addition, IRP was associated with Chicago classification type.