339 OPTIMAL CUTOFF VALUE OF INTEGRATED LOWER ESOPHAGEAL SPHINCTER RELAXATION PRESSURE FOR ACHALASIA USING STARLET HIGH-RESOLUTION MANOMETRY SYSTEM

Abstract The Starlet high-resolution manometry (HRM) system is currently used in Japan. HRM provides integrated relaxation pressure (IRP) of which value represents adequacy of lower esophageal sphincter (LES) relaxation. The upper limit of normal IRP for the Starlet was proposed as 26 mmHg using healthy subjects. However, few studies have addressed whether this cutoff may well-distinguish patients diagnosed with/without achalasia. We propose the optimal cutoff of IRP for detecting achalasia using the Starlet. Methods Patients who underwent HRM test using the Starlet system at our institution between July 2018 and December 2019 were included. Of these, we excluded patients who had a history of achalasia surgery and/or endoscopic intervention, or whose HRM testing of poor quality. Achalasia was diagnosed if impaired esophageal emptying was evident based on timed barium esophagogram, upper endoscopy, and/or computed tomography. The optimal cutoff value of IRP was estimated using the receiver operating characteristic curve analysis. We further investigate difference in IRP values between achalasia subtypes to identify characteristics of patients who are more likely to be misdiagnosed. Results In total, 145 patients met study criteria. The mean age in our cohort was 52.5 ± 15.5 years, 89 patients (61.4%) were men. Of these, 42 patients (29.0%) were diagnosed with achalasia. In achalasia patients, IRP values extended to a wide-range from minimal 18.7 to maximal 63.9 mmHg. The optimal cutoff value of IRP was 24.7 mmHg with sensitivity 90.5% and specificity 90.3% (AUC 0.96 [95% CI; 0.92¬ to 0.99]). Patients with achalasia type I based on Chicago classification were most likely to have IRP value below the threshold of 25 mmHg (4/19 patients [21.1%]). Conclusion The optimal cutoff value of IRP to distinguish achalasia was ≥25 mmHg using the Starlet HRM system. This value was nearly close to the upper limit of normal IRP value of 26 mmHg in healthy volunteers. Achalasia type I was more likely to have normal IRP value indicating that comprehensive foregut assessment (eg, timed barium esophagogram, upper endoscopy, and computed tomography) is still valuable for management of achalasia.