Flip Technology for Assessing Esophageal Structural and Motor Disorders: a Skeptic's View

Functional lumen impedance (FLIP) technology has become commercially available to assess structural and motor abnormalities of the esophagus. Increasing numbers of papers have described novel findings with this technology. This review examines the validity of the FLIP technique, how it compares with existing diagnostic modalities, and evidence to date on diagnostic accuracy.

FLIP studies require deep sedation at the time of endoscopy to complete. They assess a simulated state of esophageal obstruction in only a distal part of the esophagus rather than deglutitive motor function of the entire esophagus. The available normative dataset is small and not matched to the older age of patients typically being evaluated. The test-retest agreement in health and disease is unknown, as is the operator dependence on performing and interpreting findings. Studies to date have largely excluded patients with structural disorders, which FLIP cannot reliably distinguish from motor disorders. FLIP is an expensive technology that has been made clinically available without its true utility being established. For FLIP to be deemed a device ready for widespread clinical use, additional studies on validity, diagnostic accuracy, and outcomes need to be performed. Prospective clinical studies need to include all patients and assess the incremental cost-effectiveness of FLIP over more innovative use of existing technology, such as high-resolution manometry with provocative challenges.