Limitations of 24-hour MII-pH monitoring to diagnose functional heartburn: a diagnostic reassessment.

Functional heartburn (FH) is typically diagnosed by 24-hour multichannel intraluminal impedance-pH (MII-pH) monitoring; however, relying solely on 24-hour MII-pH may miss gastroesophageal reflux events due to day-to-day variability. In addition, since FH is a diagnosis of exclusion, other underlying conditions may be undiagnosed. This study aimed to assess the clinical course of FH and identify potential alternative diagnoses. Patients with heartburn refractory to proton pump inhibitors or potassium-competitive acid blockers who underwent endoscopy, high-resolution manometry, and MII-pH monitoring after discontinuation of acid-suppressive therapy and met diagnostic criteria for FH were retrospectively analyzed. Symptom severity was assessed using the frequency scale for the symptoms of GERD. Of 114 patients with refractory heartburn, 46 (40.4%) were diagnosed with FH. Of them, 42 patients were included in the analysis. During a mean follow-up of 18.1 months, six patients underwent hypopharyngeal impedance-pH monitoring, and four were diagnosed with laryngopharyngeal reflux disease; one of them underwent laparoscopic anti-reflux surgery, resulting in symptomatic improvement. Additionally, one patient each was diagnosed with unstable angina, atlantoaxial subluxation, major depressive disorder, bipolar disorder, and somatoform disorder. Patients with unstable angina and atlantoaxial subluxation underwent the treatment of underlying conditions and had complete resolution of symptoms. Approximately 20% of patients initially diagnosed with FH were subsequently found to have alternative diagnoses. One-time, conventional 24-hour MII-pH testing may not be accurate to diagnose FH. Therefore, even after the initial diagnosis of FH, a meticulous long-term follow-up remains essential to identify initially unrecognized conditions.